1.2. Comparison to the original Jrk controllers

This section lists most of the things you should consider if you have an existing application using the original Jrk 21v3 or Jrk 12v12 controllers and are considering upgrading to a Jrk G2.

Motor driver improvements

Compared to the original Jrk controllers, the discrete MOSFET H-bridges on the Jrk G2 18v19, 24v13, 18v27, and 24v21 support higher operating voltages and larger output currents. Additionally, those Jrk G2 models have configurable hardware current limiting: when the motor current exceeds a configurable threshold, the motor driver uses current chopping to actively limit it.

The Jrk G2 21v3 uses a TB9051FTG motor driver that features hardware current chopping with a fixed threshold of approximately 6.5 A.

Physical connection changes

You will need to keep some things in mind when updating the physical connections of an existing application:

  • The Jrk G2 circuit boards have different dimensions, mounting hole locations, and pin locations.
  • On the Jrk G2, the RC pulse input should be connected to the pin named RC instead of RX.
  • On the Jrk G2, analog control inputs should be connected to SDA/AN instead of RX.
  • An analog control potentiometer should generally be powered from SCL and GND if you want to detect disconnection (instead of AUX and GND).
  • The Jrk G2 does not have a pin named FB: analog feedback signals should be connected to the FBA pin and frequency/tachometer feedback signals should be connected to the FBT pin.
  • An analog feedback potentiometer should generally be powered from AUX and POT− (21v3, 18v19, and 24v13 only), or AUX and GND.
  • Unlike the FB pin on the original jrks, the FBA pin does not have a pull-up resistor. If you need one, you can add it externally or connect FBA to FBT to take advantage of the FBT pull-up resistor.
  • The Jrk G2 uses a USB Micro-B connector (the original Jrks used Mini-B).

Configuration and software changes

There are several changes to keep in mind when configuring the Jrk G2 or updating any software that communicates with it:

  • The Jrk G2 uses different configuration software from the original Jrk controllers. It is open source and works on Windows, Linux, and macOS. See Section 3 for installation instructions.
  • The Jrk G2 serial protocol is generally a superset of the original Jrk serial protocol, so in many cases, serial interface software running on a microcontroller or computer (using the Jrk’s RX and TX lines or its virtual USB serial ports) will not need to be modified to work with the Jrk G2.
  • The Jrk G2 native USB interface uses different product IDs and supports a different set of USB commands. However, the “Set target” and “Motor off” commands are unchanged.
  • The “detect baud rate” feature was removed, so you will need to configure the baud rate of your Jrk ahead of time using the Jrk G2 Configuration Utility if you are controlling it over serial with a microcontroller.
  • The default “Feedback mode” on the Jrk G2 is “None” instead of “Analog”.
  • On the Jrk G2, the analog control input pin (SDA/AN) does not have its pull-up resistor enabled by default, but there is an option to enable it in the “Pin configuration” tab of the Jrk G2 configuration utility. (The original Jrk always enabled a pull-up on RX, which served as the analog input.)
  • The Jrk G2’s “Feedback deadzone” feature has been changed so that it applies to “Duty cycle target” instead of “Duty cycle”, which makes it compatible with the new deceleration limits.
  • The Jrk G2’s “Duty cycle” variable will move towards zero (either immediately or limited by the configurable deceleration limit) when there is an error, so the Jrk G2 will respect acceleration limits properly once the error is resolved.
  • The 8-bit “Current” variable (which can be fetched with the serial command 0x8F) has units of 256 mA on the Jrk G2. A new 16-bit current variable is available with higher resolution.
  • Unlike the original Jrk controllers, the Jrk G2 does not reset the state of all of its error flags when you click “Apply settings” in the configuration utility. Error flags will generally be preserved.
  • The current limiting and current regulation options have changed. See Section 7.6 for details.

New features

The Jrk G2 also supports a variety of new, optional features. These features were added in a backward-compatible way and should not have an effect on your application unless you purposely use them. Some of the most notable new features are:

  • The Jrk G2 has configurable deceleration limiting. Additionally, you can choose which errors respect the deceleration limits.
  • The Jrk G2 has a new “Wraparound” option for analog feedback, which is useful for systems that continuously rotate over a full circle.
  • PID coefficients and many other settings can be adjusted on the fly over serial, I²C, or USB, using the new “Set RAM settings” command.
  • The new “Force duty cycle target” command lets you override the result of the PID algorithm.
  • The new “Force duty cycle” command lets you override the result of the PID algorithm while also ignoring acceleration and deceleration limits.
  • New frequency feedback options allow closed-loop speed control using a much larger range of tachometer frequencies.
  • Measurements of the RC input, analog control input, analog feedback input, and the tachometer input can all be enabled even if the Jrk’s main algorithm is not using them to control the motor.
  • The Jrk G2’s new I²C interface provides another option to connect a microcontroller to the Jrk, and allows you to control multiple Jrks without using AND gates or level shifters.
  • The Jrk G2 can measure the voltage of its VIN power supply and provide this reading over serial, I²C, and USB.

Related Products

Jrk G2 18v19 USB Motor Controller with Feedback
Jrk G2 24v13 USB Motor Controller with Feedback
Jrk G2 18v27 USB Motor Controller with Feedback
Jrk G2 24v21 USB Motor Controller with Feedback
Jrk G2 21v3 USB Motor Controller with Feedback
Jrk G2 21v3 USB Motor Controller with Feedback (Connectors Soldered)
Log In
Pololu Robotics & Electronics
Shopping cart
(702) 262-6648
Same-day shipping, worldwide
Shop Blog Forum Support
My account Comments or questions? About Pololu Contact Ordering information Distributors