Pololu Motoron Motor Controller User’s Guide

The Motoron motor controllers are a family of general-purpose modules designed to control brushed DC motors. The Motoron receives commands via I²C or UART serial (depending on which model you have), so only two I/O lines are needed regardless of how many Motorons you connect.

Features and specifications

• Control interface: I²C or UART serial (depending on the model)
  • I²C clock speed: up to 400 kHz
  • UART serial baud rate: up to 250,000 bps
• Optional cyclic redundancy checking (CRC)
• Configurable motion parameters:
  • Max acceleration/deceleration forward/reverse
  • Starting speed forward/reverse
  • Direction change delay forward/reverse
• PWM frequency: eight options available from 1 kHz to 80 kHz
• Command timeout feature stops motors if the Motoron stops receiving commands
• Configurable automatic error response
• Motor power supply (VIN) voltage measurement
• Two status LEDs
• Motor direction indicator LEDs
• Motoron Arduino library simplifies getting started with an Arduino or compatible controller
• Motoron Python library simplifies using the Motoron with Python or MicroPython

Available versions

The Motoron motor controllers are divided into three different classes with different operating voltage ranges and maximum currents.

• Each Motoron in the 550 class operates from 1.8 V to 22 V and can provide a maximum continuous current of 1.6 A to 1.8 A per motor (depending on the model).
  • Motoron M1x550 Single Motor Controllers
  • Motoron M2x550 Dual Motor Controllers
  • Motoron M3S550 Triple Motor Controller Shield for Arduino
  • Motoron M3H550 Triple Motor Controller for Raspberry Pi
• Each Motoron in the 256 class operates from 4.5 V to 48 V and can provide a maximum continuous current of 1.8 A to 2.2 A per motor (depending on the model).
  • Motoron M1x256 Single Motor Controllers
  • Motoron M2x256 Dual Motor Controllers
  • Motoron M3S256 Triple Motor Controller Shield for Arduino
  • Motoron M3H256 Triple Motor Controller for Raspberry Pi
• Each Motoron in the high-power class has a minimum operating voltage of 6.5 V, can operate up to 30 V or 40 V (depending on the model), and can provide a maximum continuous current of 14 A to 20 A (depending on the model). These high-power models have current sensing and configurable hardware current limiting.
  • Motoron M2S Dual High-Power Motor Controllers for Arduino
  • Motoron M2H Dual High-Power Motor Controllers for Raspberry Pi

Each of the links in the list above goes to a category on the Pololu website that contains several different Motoron products. Visit the links above to learn the details for each Motoron product, including its operating voltage range, maximum current, control interface, number of channels, and what hardware comes included or soldered.

For tables showing all the different Motoron products, see the Motoron category on the Pololu website.

We would be delighted to hear from you about any of your projects and about your experience with the Motoron. If you need technical support or have any feedback you would like to share, you can contact us directly or post on our forum. Tell us what we did well, what we could improve, what you would like to see in the future, or anything else you would like to say!

The information in this section can help you select a power supply and motor that will work with the Motoron.

The Motoron is designed to work with brushed DC motors. These motors have two terminals such that when a DC voltage is applied to the terminals, the motor spins.

When selecting the components of your system, you will need to consider the voltage and current ratings of each component:

• The voltage range of your power supply is the range of voltages you expect your power supply to produce while operating. There is usually some variation in the output voltage so you should treat it as a range instead of just a single number. In particular, keep in mind that a fully-charged battery might have a voltage that is significantly higher than its nominal voltage.
• The current limit of a power supply is how much current the power supply can provide. Note that the power supply will not force this amount of current through your system; the properties of the system and the voltage of the power supply determine how much current will flow, but there is a limit to how much current the power supply can provide.
• The operating voltage range of a Motoron is the absolute range of voltages that can be supplied to the Motoron’s VIN and GND pins, which power the motors. The Motoron requires a DC power supply. The operating voltage range of each Motoron is listed on the Motoron category page and on each Motoron’s product page, both in the summary at the top and in the “Specifications” tab.
• The continuous output current per channel of a Motoron is the maximum amount of current that the Motoron can continuously provide to each motor. The output current for each Motoron is listed on the Motoron category page and on each Motoron’s product page, both in the summary at the top and in the “Specifications” tab.
• The rated voltage of a DC motor is the voltage at which the DC motor was designed to run. You can apply voltages to the motor that are higher or lower than its rated voltage, but higher voltages bring a risk of overheating the motor or reducing its lifetime.
• The no-load current of a DC motor is the current that the motor will draw if you apply the rated voltage to the motor while its output is not connected to anything.
• The stall current of a DC motor is the current that the motor will draw if you apply the rated voltage to the motor while forcing its output shaft to remain stationary.

There are guidelines you should be aware of when selecting the components of your system:

1. The voltage of your power supply should generally be greater than or equal to the rated voltage of each DC motor. Otherwise, you will not get the full performance that the motor was designed for. If your power supply’s voltage is much higher than the rated voltage of a DC motor, you might account for that by using lower speeds for that motor in your commands to the Motoron.
2. The voltage of your power supply should be within the operating voltage range of the Motoron. Otherwise, the Motoron could malfunction or (in the case of high voltages) be damaged. Additionally, we recommend that the voltage of your power supply should be at least 6 V less than the absolute maximum, which leaves a safety margin for ripple voltage on the supply line. Note that a fully-charged battery will have a voltage much higher than the nominal voltage.
3. The typical current draw you expect for each motor should be less than the Motoron’s continuous current per motor. Each motor’s typical current draw will depend on your power supply voltage, the speeds you command the motor to move, and the current ratings of the motor. For the Motoron M1T550, M1U550, M2T550, M2U550, M3S550, M3H550, M1T256, M1U256, M2T256, M2U256, M3S256, and M3H256, a motor that draws too much current could trigger the Motoron’s overcurrent or overtemperature faults, which shut down the motor. For the Motoron M2S and M2H, a motor that draws too much current could cause the board to overheat, resulting in permanent damage.
4. The current limit of the power supply should be higher than the typical total current draw for all the motors in your system. Furthermore, it is generally good for the current limit to be much higher than that so your system can smoothly handle the times where the motors are drawing more than the typical current, for example when they are accelerating or encountering extra resistance.

This section explains how to connect motor power, motors, and a microcontroller to the Motoron M1T550, M2T550, M1T256, and M2T256, micro-sized controllers with an I²C interface.

Typical wiring diagram for connecting a microcontroller to a Motoron M1T256/M1T550 Single I²C Motor Controller.

Typical wiring diagram for connecting a microcontroller to a Motoron M2T256/M2T550 Dual I²C Motor Controller.

A Raspberry Pi Pico on a breadboard using a Motoron M2T256/M2U256 Dual Motor Controller to control two motors.

Making connections

You can buy a version of the Motoron that comes with male header pins already soldered, or you can buy a version with header pins included and do the soldering yourself. After your Motoron has header pins securely soldered to it, you can push the Motoron into a breadboard or connect its pins to jumper wires. Alternatively, you can make connections by directly soldering wires to the board. Regardless of which of these methods you choose, soldering is necessary to make reliable connections.

Connecting motor power and motors

The negative terminal of the motor power supply should be connected to the GND pin on the Motoron that is adjacent to VIN. The positive terminal of the motor power supply should be connected to the VIN pin. Note that connecting power to VIN does not power the Motoron’s microcontroller and does not cause any LEDs to turn on.

Each motor should have one lead connected to an MxA pin (M1A or M2A) and the other lead connected to the MxB pin with the matching motor number. The Motoron’s concept of “forward” corresponds to MxA driving high while MxB drives low, so you might consider this when deciding which motor lead connects to which Motoron pin. You can also flip the wires later if you want to flip the direction of motion.

Connecting a controller

You will need a controller with an I²C interface to send commands to the Motoron. The Motoron’s GND, SCL, and SDA pins should be connected to the corresponding pins of the controller board, and the Motoron’s logic voltage (VDD) should be connected to the logic voltage supply of the controller board (the allowable logic voltage range can be found in the specifications for your particular Motoron). The Motoron does not supply power to the controller board.

Once you make the GND and logic power connections and turn on the logic power, you should see the Motoron’s yellow LED blink. The red LED will also turn on unless something is communicating with the Motoron and causing it to turn the LED off.

You can connect multiple Motorons to the same I²C bus. To control multiple Motorons on the same I²C bus independently, you will need to configure each Motoron to have a unique I²C address, as described in Section 3.5.

This section explains how to connect motor power, motors, and a microcontroller to the Motoron M1U550, M2U550, M1U256, and M2U256, micro-sized controllers with a UART serial interface.

Typical wiring diagram for connecting a microcontroller to a Motoron M1U256/M1U550 Single Serial Motor Controller.

Typical wiring diagram for connecting a microcontroller to a Motoron M2U256/M2U550 Dual Serial Motor Controller.

A Raspberry Pi Pico on a breadboard using a Motoron M2T550/M2U550 Dual Motor Controller to control two motors.

Making connections

You can buy a version of the Motoron that comes with male header pins already soldered, or you can buy a version with header pins included and do the soldering yourself. After your Motoron has header pins securely soldered to it, you can push the Motoron into a breadboard or connect its pins to jumper wires. Alternatively, you can make connections by directly soldering wires to the board. Regardless of which of these methods you choose, soldering is necessary to make reliable connections.

Connecting motor power and motors

The negative terminal of the motor power supply should be connected to the GND pin on the Motoron that is adjacent to VIN. The positive terminal of the motor power supply should be connected to the VIN pin. Note that connecting power to VIN does not power the Motoron’s microcontroller and does not cause any LEDs to turn on.

Each motor should have one lead connected to an MxA pin (M1A or M2A) and the other lead connected to the MxB pin with the matching motor number. The Motoron’s concept of “forward” corresponds to MxA driving high while MxB drives low, so you might consider this when deciding which motor lead connects to which Motoron pin. You can also flip the wires later if you want to flip the direction of motion.

Connecting a controller

You will need a controller with a UART serial interface to send commands to the Motoron. The Motoron’s GND pin should be connected to a ground pin of the controller board. The Motoron’s RX pin should be connected to the TX pin of the controller board. If you want to read data from the Motoron, then the Motoron’s TX pin should be connected to the RX pin of the controller board. The Motoron’s logic voltage (VDD) should be connected to the logic voltage supply of the controller board (the allowable logic voltage range can be found in the specifications for your particular Motoron). The Motoron does not supply power to the controller board.

Once you make the GND and logic power connections and turn on the logic power, you should see the Motoron’s yellow LED blink. The red LED will also turn on unless something is communicating with the Motoron and causing it to turn the LED off.

This section explains how to connect motor power, motors, and a microcontroller to the Motoron M3S550, M3S256 and the M2S family, which are designed to be shields for an Arduino.

Connecting terminal blocks

For the Motoron M3S550 and M3S256, we generally recommend using green 3.5mm-pitch terminal blocks for the motor power and motor connections. If you have an assembled version of the Motoron, these terminal blocks come soldered to the board. Otherwise, you will need to solder them yourself. They should be soldered to the larger through holes for board power and motor outputs (GND, VIN, M1A, M1B, M2A …).

You can use blue 5mm-pitch terminal blocks if your current requirements are not too high and you can ensure that there is adequate spacing between any stacked boards in your system to prevent short circuits. This type of terminal block is included with the Motoron M3S550, M3S256, and M2S kit versions and comes soldered to the fully assembled versions of the Motoron M2S controllers. The 5mm blue terminal blocks are rated for 16 A so for higher-current applications we recommend soldering thick wires directly to the board. If you decide to use the 5mm terminal blocks, we recommend using the tabs on the side of the terminal blocks to connect them together before soldering them to the Motoron (see our video about how to install terminal blocks for more information).

We recommend only using the 5mm blue terminal blocks on Motoron shields that are at the top of a stack. Using those terminal blocks on two adjacent boards in a stack is likely to cause short circuits because they are taller than the headers.

The terminal blocks on the Motoron M2S high-power motor drivers are taller than the headers, so they should only be installed on the top Motoron in the stack.

Three Motoron M3S256 or M3S550 shields attached to an Arduino Uno, showing the spacing of the 3.5 mm terminal blocks.

Connecting motor power and motors

Motor power and motor connections for a Motoron M3S256, M3S550, M3H256, or M3H550 Triple Motor Controller.

Motor power and motor connections for a Motoron M2S Dual High-Power Motor Controller.

The negative terminal of the motor power supply should be connected to the Motoron’s large GND pin or the smaller pins next to it. The positive terminal of the motor power supply should be connected to the Motoron’s large VIN pin or the smaller pins next to it. These GND and VIN connections are required for each Motoron in a stack of Motorons. Connecting two Motorons via stackable headers does not connect their VIN pins at all, and it does not connect their GND pins in a way that is meant to carry the large currents involved in motor control. Note that connecting power to VIN does not power the Motoron’s microcontroller and does not cause any LEDs to turn on.

Each motor should have one lead connected to an MxA pin (M1A, M2A, or M3A) and the other lead connected to the MxB pin with the matching motor number. The Motoron’s concept of “forward” corresponds to MxA driving high while MxB drives low, so you might consider this when deciding which motor lead connects to which Motoron pin. You can also flip the wires later if you want to flip the direction of motion.

Connecting a controller

Motoron M3S550 shield being controlled by an Arduino Uno.

Motoron M2S shield being controlled by an Arduino Leonardo.

The Motoron shields for Arduino are designed to be plugged into the female headers of an Arduino or Arduino-compatible board that has the shape of the Arduino Leonardo or Arduino Uno R3 using stackable female headers or male headers soldered to the Motoron.

Plugging the Motoron into a controller this way connects the GND, SDA, and SCL pins of both boards, allowing the Arduino to communicate with the Motoron via I²C. It also powers the Motoron’s microcontroller from the Arduino’s IOREF pin. For most Motoron shields, the Motoron’s logic voltage (which powers the microcontroller) comes directly from IOREF. On the Motoron M3S550 shield, the IOREF pin supplies power to a 3.3 LDO regulator and the output of that regulator is the logic voltage.

Motoron M2S shield being controlled by an Arduino Uno. Electrical tape is used on the USB Type-B connector to help prevent shorts.

If you plug a Motoron M2S shield directly into an Arduino Uno or similar board, the tall USB connector can touch the Motoron and potentially cause a short circuit. Although that part of the Motoron M2S shield is protected by an insulating solder mask, we recommend adding electrical tape to the top of the USB connector to protect against this, as shown above.

The Motoron does not need to be connected directly to the Arduino: it can be connected through another shield (including other Motoron shields) as long as those boards pass the GND, SCL, SDA, and logic voltage connections through.

You can also connect the Motoron to a controller board that has a different shape as long as you make the same connections. The Motoron’s GND, SCL, and SDA pins should be connected to the corresponding pins on the controller board, and IOREF should be connected to the logic voltage supply of the controller board (the allowable logic voltage range can be found in the specifications for your particular Motoron).

A Raspberry Pi Pico on a breadboard using a Motoron M3S256 shield to control three motors.

A Raspberry Pi Pico on a breadboard using a Motoron M2S shield to control motors. A voltage regulator soldered to the Motoron powers the Pico.

After you have connected one Motoron shield to a controller, you can connect other Motoron shields to the same controller simply by stacking them above or below the first one.

Once you make the GND and logic power connections and turn on the logic power, you should see the Motoron’s yellow LED blink. The red LED will also turn on unless something is communicating with the Motoron and causing it to turn the LED off.

Powering the Arduino

By default, the Motoron does not supply power to the Arduino, so you will need to power your Arduino separately. However, there are options for powering the controllers, as documented in Section 4.3 for the M3S550/M3S256 and Section 4.5 for the M2S shields.

This section explains how to connect motor power, motors, and a microcontroller to the Motoron M3H550, M3H256 and the M2H family, which are designed to be plugged into a Raspberry Pi.

Connecting terminal blocks

For the Motoron M3H550 and M3H256, we generally recommend using green 3.5mm-pitch terminal blocks for the motor power and motor connections. If you have an assembled version of the Motoron, these terminal blocks come soldered to the board. Otherwise, you will need to solder them yourself. They should be soldered to the larger through holes for board power and motor outputs (GND, VIN, M1A, M1B, M2A, …).

You can use blue 5mm-pitch terminal blocks if your current requirements are not too high and you can ensure that there is adequate spacing between any stacked boards in your system to prevent short circuits. This type of terminal block is included with the Motoron M3H550, M3H256 and M2H kit versions and come soldered to the fully assembled versions of the Motoron M2H controllers. The 5mm blue terminal blocks are rated for 16 A so for higher-current applications we recommend soldering thick wires directly to the board. If you decide to use the 5mm terminal blocks, we recommend using the tabs on the side of the terminal blocks to connect them together before soldering them to the Motoron (see our video about how to install terminal blocks for more information).

If you want to stack multiple Motorons using 5mm terminal blocks, should trim the terminal block leads on the bottom side of the board (e.g. using a flush cutter) and use hex nuts in addition to 11mm standoffs (both of which are provided with the assembled and kit versions) between each board to space them out.

Two Motoron M2H boards with terminal blocks can be stacked if you trim the leads on the terminal blocks and space out each board using hex nuts in addition to the 11mm standoffs.

Connecting motor power and motors

Motor power and motor connections for a Motoron M3S256, M3S550, M3H256, or M3H550 Triple Motor Controller.

Motor power and motor connections for a Motoron M2H Dual High-Power Motor Controller.

The negative terminal of the motor power supply should be connected to the Motoron’s large GND pin or the smaller pins next to it. The positive terminal of the motor power supply should be connected to the Motoron’s large VIN pin or the smaller pins next to it. These GND and VIN connections are required for each Motoron in a stack of Motorons. Connecting two Motorons via stackable headers does not connect their VIN pins at all, and it does not connect their GND pins in a way that is meant to carry the large currents involved in motor control. Note that connecting power to VIN does not power the Motoron’s microcontroller and does not cause any LEDs to turn on.

Each motor should have one lead connected to an MxA pin (M1A, M2A, or M3A) and the other lead connected to the MxB pin with the matching motor number. The Motoron’s concept of “forward” corresponds to MxA driving high while MxB drives low, so you might consider this when deciding which motor lead connects to which Motoron pin. You can also flip the wires later if you want to flip the direction of motion.

Connecting a controller

A Motoron M3H256 being controlled by a Raspberry Pi.

A Motoron M2H dual motor controller being controlled by a Raspberry Pi.

The Motoron M3H256 is designed to be plugged into pins 1 through 20 of a Raspberry Pi using female headers. The Motoron M2H is designed to be plugged into the 40-pin connector of a Raspberry Pi using female headers.

Plugging the Motoron into a controller this way connects the GND, SDA, and SCL pins of both boards, allowing the controller to communicate with the Motoron via I²C. It also powers the Motoron’s microcontroller by connecting the Raspberry Pi’s 3V3 pin to the Motoron’s logic voltage.

The Motoron does not need to be connected directly to the Raspberry Pi: it can be connected through another board (including other Motoron boards) as long as those boards pass the GND, SCL, SDA, and logic voltage connections through.

You can also connect the Motoron to a controller board that has a different shape as long as you make the same connections. The Motoron’s GND, SCL, and SDA pins should be connected to the corresponding pins on the controller board, and the Motoron’s logic voltage (labeled IOREF or 3V3 depending on which type of Motoron you have) should be connected to the logic voltage supply of the controller board (the allowable logic voltage range can be found in the specifications for your particular Motoron).

An Arduino Micro on a breadboard using a Motoron M3H256 to control three motors.

After you have connected one Motoron to a controller, you can connect other Motorons to the same controller simply by stacking them above or below the first one.

Once you make the GND and logic power connections and turn on the logic power, you should see the Motoron’s yellow LED blink. The red LED will also turn on unless something is communicating with the Motoron and causing it to turn the LED off.

If you are planning to stack multiple Motoron M2H controllers, note that the procedure for setting their I²C addresses (as documented in Section 3.4) requires access to the GND and JMP1 pins, but those pins are in the middle of the board. Therefore, we recommend connecting and setting up one Motoron at a time before connecting the next one.

Powering the Raspberry Pi

By default, the Motoron does not supply power to the Raspberry Pi, so you will need to power your Raspberry Pi separately. However, there are options for powering the Raspberry Pi, as documented in Section 4.4 for the M3H550/M3H256 and Section 4.6 for the M2H controllers.

This section explains how to enable the correct I²C bus on your Raspberry Pi, make sure that your user has permission to access it, and test your setup.

The Motoron is designed to connect to the I2C1 bus on the Raspberry Pi, which uses GPIO pin 2 for SDA and GPIO pin 3 for SCL. If you are using Raspberry Pi OS, this bus is represented by /dev/i2c-1: that is the name of the device node that programs on your Raspberry Pi will open in order to communicate with the Motoron or any other targets on the bus.

Try typing ls /dev/i2c* to list your system’s available I²C busses. If /dev/i2c-1 is not in the list then you should run sudo raspi-config nonint do_i2c 0 to enable it. You must reboot your Raspberry Pi for this change to take effect.

We recommend adding your user to the i2c group so you can access the Motoron and other I²C devices without using sudo. Run the groups command to see what groups your user belongs to. If i2c is not in the list, then you should add your user to it by running sudo usermod -a -G i2c $(whoami), logging out, and then logging in again.

After you have enabled I²C and connected your Motoron to your Raspberry Pi’s I²C bus, run i2cdetect -y 1. If everything is set up correctly, you should see output like this:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: 10 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

This output means that the Raspberry Pi detected a device at address 16 (0x10 in hex), which is the default I²C address used by the Motoron.

If you have one Motoron and it is the only I²C target device in your system, there is no need to change the Motoron’s I²C address and you can skip this section.

Each device on an I²C bus should have a unique address so that you can communicate with the device without interfering with other devices on the bus. By default, the Motoron uses I²C address 16, so if you have connected two or more Motorons to your bus, or you have another device that uses address 16, you will need to change the I²C addresses of one or more Motorons.

If you need to change your Motoron’s I2C address, the recommended procedure for setting the I²C address of one or more Motorons that are connected to the I²C bus of your Raspberry Pi is:

1. Ensure that the JMP1 pin on each Motoron is not connected to anything.
2. Download the Motoron Motor Controller Python library for Raspberry Pi, and install its dependencies, as described in the “Getting started” section of its README file.
3. In a Terminal, use cd to navigate into the directory holding the library and its examples.
4. Run ./set_i2c_addresses_example.py. This utility will print some information and then prompt you for a command.
5. Perform a scan of the I²C bus by typing “s” and pressing Enter. You should get output that looks like this:

   Scanning for I2C devices…
   Found device at address 0
   Found device at address 16
   Done.

   The scan detects that a device on the bus is responding to address 16 because that is the Motoron’s default address. It also detects a device on address 0 because that is the I²C general call address and all Motorons respond to it by default, in addition to the normal address. We will use address 0 to send commands in later steps, so if the scan does not detect any devices on address 0, those steps will probably fail.
6. Warning: If you have devices on your I²C bus that are not Motorons, the steps below could cause undesired behavior by sending commands to them that are intended for the Motorons. You might consider removing those devices from your bus temporarily.
7. Connect the JMP1 pin of one Motoron to GND. If you have not soldered headers to the JMP1 pin and its adjacent GND pin, you can connect those two pins together using a wire, test clip, or with a shorting block attached to a 1×2 male header. Connecting JMP1 to GND is how we select which Motoron’s address will be changed in the next step. Only one Motoron at a time should have its JMP1 pin connected to GND.
8. Set the address of the selected Motoron by typing “a”, followed by the address (in decimal), and then pressing Enter. We recommend picking an address between 8 and 119 that is not in use by any other devices on your bus (numbers outside that range could work too, but they are reserved for other uses by the I²C specification). For example, type “a17” to set the address of the Motoron to 17. Alternatively, you can just send “a” by itself in order to have the program automatically pick an address for you, starting at 17 and skipping addresses that are already in use on the bus.
   
   This sends a “Write EEPROM” command to all of the Motorons using address 0, but the command will only have an effect on the one Motoron whose JMP1 line is low. That Motoron will record the address in its non-volatile EEPROM memory, but will not start using it yet.
9. Disconnect the JMP1 pin from GND.
10. Repeat the last three steps for every Motoron whose address you wish to change.
11. Type “r” to make the new addresses take effect. This sends a “Reset” command to all of the Motorons using address 0. Alternatively, you can power cycle the system or use the RST pin to reset the Motorons.
12. Perform another scan of the I²C bus by typing “s”. Check that a device is now found on each of the addresses that you assigned.
13. Please note that most of the example code we provide is configured to use address 16. If you have assigned a different address to your Motoron, you will need to configure any code you run to use that same address. For example, when using the Python library, write mc = motoron.MotoronI2C(address=17) to create a MotoronI2C object that uses address 17.

If you have one Motoron and it is the only I²C target device in your system, there is no need to change the Motoron’s I²C address and you can skip this section.

Each device on an I²C bus should have a unique address so that you can communicate with the device without interfering with other devices on the bus. By default, the Motoron uses I²C address 16, so if you have connected two or more Motorons to your bus, or you have another device that uses address 16, you will need to change the I²C addresses of one or more Motorons.

If you need to change your Motoron’s I2C address, the recommended procedure for setting the I²C address of one or more Motorons that are connected to the I²C bus of your Arduino is:

1. Ensure that the JMP1 pin on each Motoron is not connected to anything.
2. Install the Motoron Arduino library using the Arduino library manager. You can open the Library Manager from the “Tools” menu by selecting “Manage Libraries…”. If necessary, see the library’s README for more information about how to install it.
3. Upload the I2CSetAddresses example to your Arduino. If the Motoron library is installed properly, you can find this example under Files > Examples > Motoron > I2CSetAddresses.
4. Open the Arduino IDE’s Serial Monitor, which you can find in the “Tools” menu.
5. Perform a scan of the I²C bus by typing “s” in the box at the top of the Serial Monitor and pressing Enter. You should get output that looks something like this:

   Scanning for I2C devices…
   Found device at address 0
   Found device at address 16
   Done.

   The scan detects that a device on the bus is responding to address 16 because that is the Motoron’s default address. It also detects a device on address 0 because that is the I²C general call address and all Motorons respond to it by default, in addition to the normal address. We will use address 0 to send commands in later steps, so if the scan does not detect any devices on address 0, those steps will probably fail.
6. Warning: If you have devices on your I²C bus that are not Motorons, the steps below could cause undesired behavior by sending commands to them that are intended for the Motorons. You might consider removing those devices from your bus temporarily.
7. Connect the JMP1 pin of one Motoron to GND. If you have not soldered headers to the JMP1 pin and its adjacent GND pin, you can connect those two pins together using a wire, test clip, or with a shorting block attached to a 1×2 male header. Connecting JMP1 to GND is how we select which Motoron’s address will be changed in the next step. Only one Motoron at a time should have its JMP1 pin connected to GND.
8. Set the address of the selected Motoron by typing “a” in the box at the top of the Serial Monitor, followed by the address (in decimal), and pressing Enter. We recommend picking an address between 8 and 119 that is not in use by any other devices on your bus (numbers outside that range could work too, but they are reserved for other uses by the I²C specification). For example, type “a17” to set the address of the Motoron to 17. Alternatively, you can just send “a” by itself in order to have the sketch automatically pick an address for you, starting at 17 and skipping addresses that are already in use on the bus.
   
   This sends a “Write EEPROM” command to all of the Motorons using address 0, but the command will only have an effect on the one Motoron whose JMP1 line is low. That Motoron will record the address in its non-volatile EEPROM memory, but will not start using it yet.
9. Disconnect the JMP1 pin from GND.
10. Repeat the last three steps for every Motoron whose address you wish to change.
11. Send “r” using the Serial Monitor to make the new addresses take effect. This sends a “Reset” command to all of the Motorons using address 0. Alternatively, you can power cycle the system or use the RST pin to reset the Motorons.
12. Perform another scan of the I²C bus by sending “s”. Check that a device is now found on each of the addresses that you assigned.
13. Please note that most of the example code we provide is configured to use address 16. If you have assigned a different address to your Motoron, you will need to configure any code you run to use that same address. For example, when using the Arduino library, write MotoronI2C mc(17); to create a MotoronI2C object that uses address 17.

The Motoron’s default settings are sufficient for most applications consisting of one Motoron and one serial controller. If you do not have a specific reason to change a setting, you can skip this section.

Each Motoron with a UART serial interface has several settings for its serial interface that are stored in its non-volatile EEPROM memory and documented in Section 7. If you want to independently control multiple Motoron controllers from a single serial transmit line, you will need to assign a unique device number to each device using the procedure below. Another common reason to use the procedure below is if you want to use a baud rate other than the default rate of 115200 bps (bits per second).

If you need to change the settings in the EEPROM of a Motoron with a UART serial interface, the recommended procedure is:

1. Connect a single Motoron to an Arduino or Arduino-compatible controller so that it can receive serial commands and send serial responses back to the Arduino. If you are not sure how to do this, refer to the Motoron library’s README.
2. To successfully follow this procedure, you will need to know what baud rate your Motoron is using. It also helps if you know whether it is configured to use 7-bit responses and whether it is configured to use 14-bit device numbers. If you are not sure about the values the Motoron is currently using for any of those serial settings, then power cycle it (or reset it) while its JMP1 pin is shorted to GND. This causes the Motoron to use 9600 baud, 8-bit responses, and 7-bit device numbers until the next time it is reset.
3. Install the Motoron Arduino library using the Arduino library manager. You can open the Library Manager from the “Tools” menu by selecting “Manage Libraries…”. If necessary, see the library’s README for more information about how to install it.
4. Open the SerialSetup example. If the Motoron library is installed properly, you can find this example under Files > Examples > Motoron > SerialSetup.
5. Find the line near the top of the code that defines assignBaudRate and other parameters. If you want your Motorons to be configured to use a baud rate other than 115200 bps, or if you want them to use non-default values for any of the other settings defined in this area of the code, then you should change the definitions there to match what you want.
6. Upload the sketch to your Arduino.
7. Open the Arduino IDE’s Serial Monitor, which you can find in the “Tools” menu. The top of the serial monitor contains a box where you can type commands and send them to the Arduino by pressing Enter.
8. If your Motoron is currently using a baud rate other than the default of 115200 bps, use the Serial Monitor to send “b” followed by the baud rate in decimal (for example, “b9600”). This configures the Arduino to use the same baud rate so the Arduino can communicate with the Motoron.
9. If your Motoron is currently using 7-bit responses or 14-bit device numbers, you should change the sketch to use the same settings so the sketch can detect the Motoron in the next step. To do this, type “o” and press Enter until the sketch reports the correct settings.
10. To check your connections and configuration, send “i”. You should get output that looks something like this:

    Identifying Motoron controllers (115200 baud, 7-bit device number, 8-bit responses)…
     16: product=0x00CF version=1.02 JMP1=off EEPROM=10 00 00 00 00 8B 00 00 
    Done.  

    This particular output shows that a Motoron M2U256 with device number 16 was detected and its EEPROM still contains factory settings. Note that the “i” command can take several minutes if you are using 14-bit device numbers, because the code checks each device number, one at a time.
11. Connect the JMP1 pin of the Motoron to GND. If you do not do this, the Motoron will ignore all commands that write to its EEPROM. This connection does not have to last for long, so it is OK to just hold it in place with your hand.
12. Type “a” followed by the device number you want to assign to the Motoron, and optionally followed by the alternative device number you want to assign. This will write to the Motoron’s EEPROM, setting its device number, setting (or disabling) its alternative device number, and applying all the hardcoded settings that you set up step 5. For example send “a 17” to assign device number 17 and disable the alternative device number.
13. Disconnect the JMP1 pin from GND.
14. Send “r” using the Serial Monitor to reset the Motoron and make the new settings take effect. Alternatively you can power cycle the Motoron or reset it with its reset pin.
15. To make sure the steps above worked and the Motoron is using the expected settings, you might want to send the “k” command followed by the “i” command. The “k” command tells the sketch to use the hardcoded serial settings that are being written to the Motorons, and “i” is the command to identify connected Motorons (as we already used above).
16. Please note that most of the example code we provide is configured to use 115200 bps, use the Compact protocol (so all devices respond to the commands regardless of their device number), and use default values for all of the Motoron’s serial settings. If you change the serial settings of your Motoron, you will most likely need to configure your code to use the same settings. The documentation of the Motoron Arduino library (and in particular the MotoronSerial class) has information about the functions you can call to do that. The baud rate your code uses is not controlled by the Motoron library: it is controlled by the argument you pass when calling begin() on the serial port object.

This section documents what you need to know to get started writing code to control the Motoron.

To control the Motoron, you need to send commands to it using its I²C or UART serial interface (whichever one it has). The commands are sequences of bytes (8-bit numbers from 0 to 255) and some of them generate responses which are also sequences of bytes. The details of what commands are supported and how to encode them in bytes are documented in Section 3.7. The details of the Motoron’s I²C interface are documented in Section 6, and the details of its UART serial interface are documented in Section 7. Numbers prefixed with “0x” here are written in hexadecimal notation (base 16), and they are written with their most significant digits first, just like regular decimal numbers.

Arduino library and examples

If you are controlling the Motoron from an Arduino or Arduino-compatible board, we recommend that you install our Motoron Arduino library and use one of the examples that comes with it as a starting point for your code. The library comes with these beginner-friendly examples, which you can find in the Arduino IDE under Files > Examples > Motoron.

• I2CSimple and SerialSimple: Show how to control the Motoron in the simplest way.
• I2CCareful and SerialCareful: Show how to shut down the motors whenever any problems are detected.
• I2CRobust and SerialRobust: Show how to ignore or automatically recover from problems as much as possible.

Each of these examples just controls one Motoron. If you are using multiple Motorons, you can create an additional MotoronI2C or MotoronSerial object for each controller, and pass the device number (address) of each Motoron to the constructor for each object. This can be done for any of the examples listed above, and the library comes with a examples named I2CSimpleMulti and SerialSimpleMulti which show how to control multiple Motorons this way.

Python library and examples

If you are controlling the Motoron from Python or MicroPython, you might consider downloading our Motoron Python library and using one of the examples that comes with it as a starting point for your code. The Python library was designed to have the same features and behave nearly the same as the Arduino library. However, one major difference is that it generally throws an exception whenever there is a communication error, whereas the Arduino library only reports errors via its getLastError() method.

Like the Arduino library, the Python library comes with these beginner-friendly examples:

• *_simple_example.py: Show how to control the Motoron in the simplest way.
• *_careful_example.py: Show how to shut down the motors whenever any problems are detected.
• *_robust_example.py: Show how to ignore or automatically recover from problems as much as possible.

Each of these examples just controls one Motoron. If you are using multiple Motorons, you can create an additional MotoronI2C or MotoronSerial object for each controller, and pass the device number (address) of each Motoron to the constructor for each object. This can be done for any of the examples listed above, and the library comes with a examples named *_multi_example.py which show how to control multiple Motorons this way.

The library also comes with examples named *_simple_no_library_example.py which are equivalent to the corresponding simple examples, but do not use the Motoron library. These examples are meant to be used as a reference for people trying to get started with the Motoron from a different programming environment, since it is easier to see exactly what bytes are being sent.

Initialization sequence

This is a sequence of commands you can run near the beginning of your code to help you get started with controlling the Motoron.

Description: Reinitialize
Bytes: 0x96 0x74

This command resets the Motoron to its default state. We recommend doing this when starting up to ensure that the behavior of your system will only depend on the code you are currently running, instead of being affected by settings that you might have set previously in an old version of your code. The bytes shown above are the command byte for the “Reinitialize” command followed by a cyclic redundancy check (CRC) byte.

Description: Disable CRC
Bytes: 0x8B 0x04 0x7B 0x43

This command disables the cyclic redundancy check (CRC) feature of the Motoron (documented in Section 11). The CRC feature is enabled by default to make the Motoron less likely to execute incorrect commands when there are communication problems. Disabling CRC makes it easier to get started writing code for the Motoron because you do not have to implement the CRC computation or append CRC bytes to each command you send. Once you have gotten your system to work, you might consider implementing CRC and removing this command to make things more robust. This is an example of the more general “Set protocol options” command, and the last byte shown above is a CRC byte.

Description: Clear reset flag
Bytes: 0xA9 0x00 0x04

This command clears (sets to 0) a bit in the Motoron called the “Reset flag”. This flag gets set to 1 after the Motoron powers on or experiences a reset, and with the default configuration it is considered to be an error, so it prevents the motors from running.This is an example of the more general “Clear latched status flags” command, and there is no CRC byte appended because we disabled the CRC feature above.

The reset flag exists to help prevent running motors with incorrect settings. In case the Motoron itself gets reset while your system is running, the Reset flag will be set and the motors will not run.

Initialization sequence (with CRC)

This is similar to the initialization sequence above, except it leaves CRC enabled.

Description: Reinitialize
Bytes: 0x94 0x74

Description: Clear reset flag
Bytes: 0xA9 0x00 0x04

The bytes at the end of each command are CRC bytes. Instead of hard coding those bytes, you should be able to calculate each one by applying the CRC algorithm to the command and data bytes immediately before it.

Command timeout

By default, the Motoron will turn off its motors if it has not received a valid command in the last 1.5 seconds. The details of the command timeout feature are documented in Section 8. This means that the motors will stop running if your microcontroller crashes, goes into programming/bootloader mode, or stops running your motor control code for any other reason. You can send a “Set variable” command to configure the timeout period or disable the feature altogether. Change the “Command timeout” variable if you want to change the amount of time it takes for the Motoron to time out, or change the “Error mask” variable if you want to disable the command timeout. The “Set variable” command and all other commands are documented in Section 9.

Current limit

The Motoron M2S and M2H controllers have configurable hardware current limiting and the default value of the current limit is generally lower than what the controller is capable of, so you might need to set the current limit to get the desired performance of your system. However, note that the current limit should be set carefully because these high-power controllers do not have meaningful over-temperature protection. For more information see the “Current limit” variable in Section 8 and see the I2CCurrentSenseCalibrate example that comes with the Arduino library.

Motion parameters

You can send a “Set variable” command (documented in Section 9) to configure how the motors move and other settings. In particular, you can set acceleration and deceleration limits for each motor and each direction of motion, which helps to reduce sudden current spikes or jerky motions.

The Motoron only stores a few settings in its non-volatile EEPROM memory. Most settings, including the motion parameters and command timeout, get reset to their default values whenever the Motoron powers on, resets, or receives a “Reinitialize” command.

Motor control

Once you have taken care of the initialization and configuration described above, you are ready to run some motors! See the “Set speed” and “Set all speeds” commands in Section 9.

Motoron M1T550 Single I²C Motor Controller pinout.	Motoron M2T550 Dual I²C Motor Controller pinout.
Motoron M1T256 Single I²C Motor Controller pinout.	Motoron M2T256 Dual I²C Motor Controller pinout.

The diagrams above identify the control and power pins on the Motoron M1T550, M2T550, M1T256 and M2T256. Section 3.2.1 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the VDD pin, and it is controlled via I²C through the SCL and SDA pins (see Section 6). Additional GND pins provide a common ground reference between the Motoron and device controlling it.

The VM pin provides access to the reverse-protected motor supply voltage.

The ERR pin drives high when the red LED is on, which usually indicates an error as described in Section 5. The ERR pin is protected by a 220Ω series resistor. When the red LED is not on, the ERR pin is pulled down weakly.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s I²C address to be changed, as detailed in Section 3.5. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the address configured in EEPROM and use 15 as its I²C address instead.

Motoron M1U550 Single Serial Motor Controller pinout.	Motoron M2U550 Dual Serial Motor Controller pinout.
Motoron M1U256 Single Serial Motor Controller pinout.	Motoron M2U256 Dual Serial Motor Controller pinout.

The diagrams above identify the control and power pins on the Motoron M1U550, M2U550, M1U256 and M2U256. Section 3.2.2 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the VDD pin, and it is controlled via UART serial through the TX and RX pins (see Section 7). Additional GND pins provide a common ground reference between the Motoron and device controlling it.

The VM pin provides access to the reverse-protected motor supply voltage.

The ERR pin drives high when the red LED is on, which usually indicates an error as described in Section 5. The ERR pin is protected by a 220Ω series resistor. When the red LED is not on, the ERR pin is pulled down weakly.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s serial settings to be changed, as detailed in Section 3.6. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the serial settings configured in EEPROM and use safe default settings instead (see Section 10).

The diagram above identifies the control and power pins on the Motoron M3S550 and M3S256. Pins that are used by the motor controller are indicated in black, while pins that are not connected to anything by default are gray (these mostly serve as extra access points for the Arduino’s pins if the Motoron is plugged in as a shield). Section 3.2.3 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the Arduino by the IOREF pin. On the Motoron M3S256, the Motoron’s logic voltage (which powers its microcontroller) comes directly from IOREF. On the Motoron M3S550, the IOREF pin supplies power to a 3.3 LDO regulator, and the output of that regulator powers the Motoron’s microcontroller and is called the logic voltage.

The Motoron is controlled via I²C through the SCL and SDA pins (see Section 6). Additional GND pins provide a common ground reference between the Motoron and Arduino.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s I²C address to be changed, as detailed in Section 3.5. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the address configured in EEPROM and use 15 as its I²C address instead.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

Powering the Arduino

The VM pins near the lower right corner of the board provide access to the reverse-protected motor supply voltage. VM can optionally be used to power the Arduino’s VIN pin (AVIN) either directly or through a regulator.

If the voltage of your motor power supply is within the allowed input voltage range for your Arduino, then you can power the Arduino by connecting the Motoron’s AVIN pin to the nearby VM pin. Doing this supplies power to Arduino’s VIN pin (AVIN) from the reverse-protected motor supply voltage (VM).

Alternatively, you can power the Arduino through a voltage regulator. The Motoron M3S550 and M3S256 have VM, GND, and AVIN pins next to each other which are designed to be connected to a regulator. The regulator should be connected in the correct orientation so that the Motoron’s VM pin is connected to the regulator’s power input and the regulator’s power output is connected to AVIN. The motor power supply must be in the allowed input voltage range of the regulator, and the regulator must produce an output voltage that is within the allowed input voltage range of the Arduino. The regulator must also be able to supply enough current for the Arduino.

To avoid shorting two power outputs together, do not connect anything to the Arduino’s DC power jack while supplying power to AVIN through the Motoron.

Powering the Arduino’s VIN from VM on a Motoron M3S550, M3S256 or M2S.

Powering the Arduino’s VIN from an external regulator connected to VM on a Motoron M3S550, M3S256, or M2S.

The diagram above identifies the control and power pins on the Motoron M3H550 and M3H256. Pins that are used by the motor controller are indicated in black, while pins that are not connected to anything by default are gray. Section 3.2.4 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the 3V3 pin, which connects to the pin of the same name on the Raspberry Pi. The Motoron is controlled via I²C through the SCL and SDA pins (see Section 6). Additional GND pins provide a common ground reference between the Motoron and the Raspberry Pi.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s I²C address to be changed, as detailed in Section 3.4. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the address configured in EEPROM and use 15 as its I²C address instead.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

The VM pin provides access to the reverse-protected motor supply voltage.

You can optionally power the Raspberry Pi by supplying 5 V to the VREG pin. To help achieve this, the Motoron M3H550 and M3H256 have adjacent VM, GND, and VREG pins which you can connect to a voltage regulator. The regulator should be connected in the correct orientation so that the Motoron’s VM pin connects to the regulator’s power input and the regulator’s power output connects to VREG. The motor power supply must be in the allowed input voltage range of the regulator, and the regulator must output 5 V (or something close enough to be tolerated by the Raspberry Pi). The regulator must also be able to supply enough current for the Raspberry Pi (e.g. 3 A for a Raspberry Pi 4). An ideal diode circuit on the Motoron prevents reverse current from flowing from the Raspberry Pi to the VREG pin if the Raspberry Pi is separately powered (for example, through its USB power receptacle). However, we do not recommend connecting external USB power to the Raspberry Pi while it is powered through the Motoron, since recent versions of the Raspberry Pi (including the 4 Model B and 3 Model B+) do not have a corresponding diode on their USB power input, so it is possible for the Motoron to backfeed a USB power adapter through the Raspberry Pi.

Powering the Raspberry Pi’s 5V pin from an external regulator connected to VM on a Motoron M3H550 or M3H256.

The 5V pin connects to the pin of the same name on the Raspberry Pi. It is also the output of the ideal diode circuit.

The diagram above identifies the control and power pins on the Motoron M2S shields (M2S18v18, M2S24v14, M2S18v20, and M2S24v16). Pins that are used by the motor controller are indicated in black, while pins that are not connected to anything by default are gray (these mostly serve as extra access points for the Arduino’s pins if the Motoron is plugged in as a shield). Section 3.2.3 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the Arduino by the IOREF pin, and it is controlled via I²C through the SCL and SDA pins (see Section 6). Additional GND pins provide a common ground reference between the Motoron and Arduino.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s I²C address to be changed, as detailed in Section 3.5. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the address configured in EEPROM and use 15 as its I²C address instead.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

Powering the Arduino

The VM pins near the lower right corner of the board provide access to the reverse-protected motor supply voltage. VM can optionally be used to power the Arduino’s VIN pin (AVIN) either directly or through a regulator.

If the voltage of your motor power supply is within the allowed input voltage range for your Arduino, then you can power the Arduino by connecting the Motoron’s AVIN pin to the nearby VM pin. Doing this supplies power to Arduino’s VIN pin (AVIN) from the reverse-protected motor supply voltage (VM).

Alternatively, you can power the Arduino through a voltage regulator. The shield has VM, GND, and AVIN pins next to each other which are designed to be connected to a regulator. The regulator should be connected in the correct orientation so that the Motoron’s VM pin is connected to the regulator’s power input and the regulator’s power output is connected to AVIN. The motor power supply must be in the allowed input voltage range of the regulator, and the regulator must produce an output voltage that is within the allowed input voltage range of the Arduino. The regulator must also be able to supply enough current for the Arduino.

To avoid shorting two power outputs together, do not connect anything to the Arduino’s DC power jack while supplying power to AVIN through the Motoron.

Powering the Arduino’s VIN from VM on a Motoron M3S550, M3S256 or M2S.

Powering the Arduino’s VIN from an external regulator connected to VM on a Motoron M3S550, M3S256, or M2S.

The diagram above identifies the control and power pins on the Motoron M2H controllers (M2H18v18, M2H24v14, M2H18v20, and M2H24v16). Pins that are used by the motor controller are indicated in black, while pins that are not connected to anything by default are gray. Section 3.2.4 explains how to connect motor power, motors, and a microcontroller.

The motor power supply should be connected to the VIN pin and adjacent GND pin, and a motor can be connected to each pair of MxA and MxB pins (e.g. M1A and M1B). For more information on choosing a power supply and motors, see Section 3.1.

The Motoron’s logic is powered from the 3V3 pin, which connects to the pin of the same name on the Raspberry Pi. The Motoron is controlled via I²C through the SCL and SDA pins (see Section 6). Additional GND pins provide a common ground reference between the Motoron and the Raspberry Pi.

The JMP1 pin can be shorted to the adjacent GND pin to allow the Motoron’s I²C address to be changed, as detailed in Section 3.4. Also, shorting JMP1 to GND at startup causes the Motoron to ignore the address configured in EEPROM and use 15 as its I²C address instead.

The RST pin can be driven low to reset the Motoron; see Section 12 for more details.

The VM pin provides access to the reverse-protected motor supply voltage.

You can optionally power the Raspberry Pi by supplying 5 V to the VREG pin. To help achieve this, the Motoron M2H has adjacent VM, GND, and VREG pins which you can connect to a voltage regulator. The regulator should be connected in the correct orientation so that the Motoron’s VM pin connects to the regulator’s power input and the regulator’s power output connects to VREG. The motor power supply must be in the allowed input voltage range of the regulator, and the regulator must output 5 V (or something close enough to be tolerated by the Raspberry Pi). The regulator must also be able to supply enough current for the Raspberry Pi (e.g. 3 A for a Raspberry Pi 4). An ideal diode circuit on the Motoron prevents reverse current from flowing from the Raspberry Pi to the VREG pin if the Raspberry Pi is separately powered (for example, through its USB power receptacle). However, we do not recommend connecting external USB power to the Raspberry Pi while it is powered through the Motoron, since recent versions of the Raspberry Pi (including the 4 Model B and 3 Model B+) do not have a corresponding diode on their USB power input, so it is possible for the Motoron to backfeed a USB power adapter through the Raspberry Pi.

Powering the Raspberry Pi’s 5V pin from an external regulator connected to VM on a Motoron M2H.

The 5V pin connects to the pin of the same name on the Raspberry Pi. It is also the output of the ideal diode circuit.

The Motoron Motor Controller has several LEDs to indicate its status.

Status LEDs

On the edge of the board, opposite the motor output pins, there are two status LEDs.

The yellow status LED indicates reset events and shows when the motor outputs are enabled.

• During the first half second after the Motoron has powered up or its processor has been reset, the yellow LED blinks 4 times.
• Otherwise, if the Motoron motor outputs are enabled or the Motoron is trying to enable them, the yellow LED is on solid. This corresponds to the “Motor output enabled” bit in the “Status flags” variable, which is documented in Section 8.
• Otherwise, if the Reset bit in the “Status flags” variable is set and it is configured to be an error, the yellow LED blinks for 0.5 s once per second. This is the default state, and it generally indicates that communication has not been established.
• Otherwise, the yellow LED blinks briefly once per second.

The red error LED usually indicates hardware issues or errors that prevent the motors from running.

• If you have a Motoron with a UART serial interface and have enabled the “ERR is DE” option, the red LED will only turn on while the Motoron is transmitting a response on its TX line.
• Otherwise, the red LED will be on solid if a motor fault is happening, motor power has been lost, or if there is a firmware-level error stopping the motors from running. More specifically, the red LED will be on if any of the “Motor faulting”, “No power”, or “Error active” flags documented in Section 8 are 1.
• Otherwise the red LED will be off.

If the red LED is off, it does not necessarily mean that the VIN power voltage is high enough for the Motoron to drive motors.

Motor direction LEDs

On the side of the board with the motor output pins, each motor has two direction indicator LEDs.

The green direction LED indicates that the voltage on the MxA pin is high while the voltage on the MxB pin is low. This direction is called forward and corresponds to a positive speed numbers.

The red direction LED indicates that the voltage on the MxB pin is high while the voltage on the MxA pin is low. This direction is called reverse and corresponds to a negative speed numbers.

Both direction LEDs get brighter if the absolute value of the speed increases, or if the motor power supply (VIN) increases.

To control the Motoron M1T550, M2T550, M3S550, M3H550, M1T256, M2T256, M3S256, M3H256, M2S, or M2H, you will need to use the Motoron’s I²C interface.

I²C is a specification for a bus that can be used to connect multiple devices. The bus uses two signal lines: SDA is the data line and is used to transmit and receive data, while SCL is the clock line is used to coordinate the flow of data. There are two types of devices that can connect to an I²C bus: a controller is a device that initiates transfers of data, generates clock signals, and terminates transfers, while a target is a device that is addressed by a controller. The Motoron acts only as a target.

I²C voltage levels

The voltages on the Motoron’s SDA and SCL lines must not exceed 6.5 V (they are 5 V tolerant). Each of these lines is pulled up with an on-board 10 kΩ pull-up resistor. On the Motoron shields for Arduino, the pull-ups connect to IOREF. On Motoron controllers for Raspberry Pi, the pull-ups connect to the 3V3 pin. On other Motorons the pull-ups connect to the VDD pin. For the signals on SDA and SCL to be read properly by the Motoron, the low level must be less than 30% of the Motoron’s logic voltage, and the high level must be more than 70% of the Motoron’s logic voltage.

I²C clock speed

The Motoron’s I²C interface supports clock speeds up to 400 kHz. It uses clock stretching to slow down the transfer of data when bytes are written faster than it can handle, or if a read transfer is started before data is available.

If your I²C controller does not support clock stretching properly, you can avoid clock stretching by limiting your write transfers to be at most 31 bytes long and delaying for 1 millisecond after each write transfer to give the Motoron time to process it.

I²C address

By default, the Motoron uses the 7-bit I²C address 16. This address is stored in the Motoron’s non-volatile EEPROM memory, and you can change it by sending a “Write EEPROM” command. If the JMP1 pin is shorted to GND at startup, the Motoron will ignore the address in EEPROM and use 15 as its I²C address instead. The Motoron determines what I²C address to use when it starts up, so any changes to the JMP1 pin or the EEPROM will not take effect until the next reset.

The Motoron also responds to the I²C general call address (0) in addition to its normal address by default. This allows you to send the same command to multiple Motoron targets simultaneously. The general call address is write-only; reading bytes from it is not supported. (However, if you send a command to the general call address that results in a response, you can read the response from an individual Motoron using its regular address.) You can use the “Set protocol options” command to disable the general call address, but it will become re-enabled the next time the Motoron is reset.

I²C protocol

There are two types of data transfers that can be initiated by an I²C controller: a write transfer writes some number of bytes to a target, and a read transfer reads some number of bytes from the target.

When you write bytes to the Motoron using write transfers, those bytes are interpreted as commands as described in Section 9. The Motoron does not care how the bytes are grouped into write transfers: you can send each command in its own transfer for simplicity, or send multiple commands together in a single transfer for extra efficiency. The Motoron acknowledges every byte written to it using I²C’s built-in acknowledgment mechanism, regardless of whether those bytes actually form valid commands.

Some Motoron commands generate responses. To read the response to a command, you can start a read transfer after writing the last byte of a command, before you have written any other bytes. (To ensure that responses do not get mixed up, the Motoron clears its stored response every time a new byte is written.) It is OK to skip reading a response if you do not need it, or to just read part of it. It is also OK to read the response using multiple read transfers.

If you read bytes via I²C at a time when there is no response data available, the Motoron will provide a value of 0xAA for each byte you read. This can happen if you read at the wrong time, or if you read too many bytes. Enabling CRC for responses (as described in Section 9) and checking the value of the CRC byte is a good way to detect if this is happening.

To control the Motoron M1U550, M2U550, M1U256 or M2U256, you will need to use the Motoron’s UART serial interface.

The RX and TX pins of the Motoron provide its serial interface. The Motoron’s RX pin is an input, and its TX pin is an output. The RX pin has a weak pull-up resistor, and each pin is protected by a 220Ω series resistor.

Serial voltage levels

The UART serial interface uses non-inverted TTL logic levels: a level of 0 V corresponds to a value of 0, and a level of VDD corresponds to a value of 1. The input signal on RX must be below 0.3×VDD to be recognized as low, and above 0.7×VDD to recognized as high. The voltage on RX must not exceed VDD by more than 0.3 V. Therefore, if the Motoron is running at 3.3 V, its RX pin is not 5 V tolerant.

Serial data format

The data format is 8 data bits, one stop bit, with no parity, which is often expressed as 8-N-1. The diagram below depicts a typical serial byte:

Diagram of a non-inverted TTL serial byte.

Serial baud rate

The UART serial interface is asynchronous, meaning that the sender and receiver each independently time the serial bits. The sender and receiver must be configured to use the same baud rate, which is typically expressed in bits per second.

By default, the Motoron uses 115200 baud. The baud rate is stored in the Motoron’s non-volatile EEPROM memory, and you can change it by sending a “Write EEPROM” command. If the JMP1 pin is shorted to GND at startup, the Motoron will ignore the baud rate in EEPROM and use 9600 baud instead. The Motoron determines what baud rate to use when it starts up, so any changes to the JMP1 pin or the EEPROM will not take effect until the next reset.

The Motoron supports baud rates from 300 to 250000 bps. It is possible to configure the Motoron to use baud rates up to 1 Mbps, but there are two potential problems with high baud rates. First of all, if the Motoron receives a rapid stream of commands using a baud rate higher than 115200, there is a risk that the Motoron firmware might not process the commands fast enough and eventually start discarding data (this condition is called a software overrun and can be detected). Secondly, the Motoron can only generate baud rates of the form 16 Mbps divided by an integer, so baud rates faster than 115200 baud cannot always be accurately generated.

Serial command protocols

The Compact protocol is the simpler and more compact of the two protocols supported by the Motoron. It is the protocol you should use if the Motoron is the only device connected to your serial line. A compact protocol command consists of a command byte with its most-significant byte set followed by the data bytes needed for the command (if there are any), each of which has its most-significant bit cleared. The Command reference section documents the specific bytes you need to send for a compact protocol command. You also need to append a cyclic redundancy check byte at the end of the command unless you have disabled CRC for commands.

The Pololu protocol can be used in situations where you have multiple devices connected to your serial line. This protocol is compatible with the serial protocol used by our other serial motor and servo controllers. As such, you can daisy-chain a Motoron on a single serial line along with our other serial controllers (including additional serial Motorons) and use the Pololu protocol to send commands specifically to the designated Motoron without confusing other devices on the line. Any compact protocol command can be transformed into a Pololu protocol command using the following process: first, clear the most significant bit of the command byte (the first byte). For example, the command byte of a normal “Set speed” command is 0xD1, and it becomes 0x51 in the Pololu protocol. Next, insert at the beginning of the command a 0xAA byte followed by a byte between 0 and 127 that specifies the device number of the Motoron you want to address. Unless you have disabled CRC for commands, you need to append a CRC byte at the end of the command and it must be calculated over the entire Pololu protocol command, including the first two bytes.

The Motoron’s device number is 16 by default. The device number is stored in the Motoron’s non-volatile EEPROM memory, and you can change it by sending a “Write EEPROM” command. If the JMP1 pin is shorted to GND at startup, the Motoron will ignore the device number in EEPROM and use 15 instead. The Motoron determines what device number to use when it starts up, so any changes to the JMP1 pin or the EEPROM will not take effect until the next reset.

You do not need to configure the Motoron ahead of time to use a specific protocol: the Motoron will detect what protocol you are using from the first byte of your command.

The Motoron can be configured to respond to an alternative device number. If the alternative device number is enabled, the Motoron will respond to commands that are addressed to either the primary device number or the alternative device number. This can be useful if you want to assign your Motorons to groups and send a single command to all the Motorons in a group, while still being able to individually address each Motoron.

Communication option: 14-bit responses

The Motoron can be configured to use a 14-bit device number. With this option enabled, the device numbers can range from 0 to 16383, instead of the typical range of 0 to 127. After the 0xAA byte, you have to send two device number bytes, both of which are between 0 and 127: the first byte holds the lower 7 bits of the device number, while the second byte holds the upper 7 bits of the device number. The format of the “Multi-device error check” and “Multi-device write” commands also change when this option is enabled.

Communication option: 7-bit responses

In general, the data sent by the Motoron in response to serial commands is arbitrary binary data: the bytes can be anything from 0 to 255. The Motoron’s 7-bit responses option causes it to encode those responses in a format that only uses values from 0 to 127. This can be useful if you have wired your Motorons in such a way that the responses from one Motoron will be seen by another Motoron, and you do not want those responses to accidentally be interpreted as commands.

The 7-bit encoding performed by the Motoron works as follows. First, if the serial response is longer than 7 bytes, the Motoron truncates it to be exactly 7 bytes long, throwing away all the bytes after the first 7. This behavior might change in future firmware versions, so we recommend that you do not request more than 7 bytes from the Motoron if you have enabled 7-bit responses. Next, the Motoron sets the most-significant bit of each byte in the response to 0. The Motoron packs the former values of those most significant bits (MSbs) into a single byte and appends it to the response. The bits of that final byte are in the same order as the bytes they correspond to: the least significant bit corresponds to the first byte, while the next bit corresponds to the second byte, and so on. The Motoron does this conversion before it computes and appends the (optional) CRC byte for the response.

Communication option: ERR is DE

Oscilloscope trace showing the ERR/DE pin of the Motoron M2U256 driving high while its TX pin sends data.

The Motoron’s ERR pin can be configured to act as a driver enable (DE) line. When the ERR is DE option is enabled, instead of indicating errors as described in Section 5, the ERR pin will drive high while the Motoron is transmitting serial data on its TX pin and drive low at other times. This feature is intended to be used in RS-485 systems where the ERR pin is connected to the driver enable (DE) pin of an RS-485 transceiver. The Motoron’s red LED is tied to the ERR pin, so its will briefly blink whenever the Motoron transmits a serial response.

8. Variable reference

uint32_t vinVoltageMv = (uint32_t)vinVoltage * referenceMv / 1024 * 1047 / 47;

uint32_t vinVoltageMv = (uint32_t)vinVoltage * referenceMv / 1024 * 459 / 47;

9. Command reference

command[0] = 0x9C;  // Set Variable
command[1] = motor & 0x7F;
command[2] = offset & 0x7F;
command[3] = value & 0x7F;
command[4] = (value >> 7) & 0x7F;

command[0] = 0xD1;  // Set Speed, normal mode
command[1] = motor & 0x7F;
command[2] = speed & 0x7F;
command[3] = (speed >> 7) & 0x7F;

command[0] = 0xB1;  // Set braking, normal mode
command[1] = motor & 0x7F;
command[2] = amount & 0x7F;
command[3] = (amount >> 7) & 0x7F;

10. EEPROM settings reference

11. Cyclic redundancy check (CRC)

#include <stdint.h>
 
uint8_t getCRC(uint8_t * message, uint8_t length)
{
  uint8_t crc = 0;
  for (uint8_t i = 0; i < length; i++)
  {
    crc ^= message[i];
    for (uint8_t j = 0; j < 8; j++)
    {
      if (crc & 1) { crc ^= 0x91; }
      crc >>= 1;
    }
  }
  return crc;
}

12. Reset pin

Related products

	Motoron M3S256 Triple Motor Controller Shield for Arduino (Connectors Soldered)
	Motoron M1T550 Single I²C Motor Controller (Header Pins Soldered)
	Motoron M3H550 Triple Motor Controller for Raspberry Pi (Connectors Soldered)
	Motoron M3S550 Triple Motor Controller Shield for Arduino (Connectors Soldered)
	Motoron M1T256 Single I²C Motor Controller (Header Pins Soldered)
	Motoron M2T256 Dual I²C Motor Controller (Header Pins Soldered)
	Motoron M2H18v18 Dual High-Power Motor Controller for Raspberry Pi (Connectors Soldered)
	Motoron M2S18v18 Dual High-Power Motor Controller Shield for Arduino (Connectors Soldered)
	Motoron M3H256 Triple Motor Controller for Raspberry Pi (Connectors Soldered)
	Motoron M2T550 Dual I²C Motor Controller (Header Pins Soldered)

Related categories

Motoron Motor Controllers