4.13. Setting up STEP/DIR control

You can set the Tic’s control mode to “STEP/DIR” to turn the Tic into a digitally-configurable stepper motor driver.

In this mode, you will need to connect a microcontroller to the Tic’s STEP and DIR pins to control the stepper motor. The STEP and DIR pins are connected through 220 Ω or 470 Ω protection resistors to the STEP and DIR inputs on the Tic’s on-board stepper motor driver IC; using them to control the driver bypasses the Tic’s speed-limiting and acceleration-limiting features, and the Tic will have no knowledge of the current position or speed of the stepper motor.

The STEP and DIR lines are pulled down by default. The driver takes one step whenever it sees a rising edge on the STEP pin, and the direction of the step is specified by the DIR pin. For detailed specifications of the STEP/DIR interface, see the MP6500 datasheet (1MB pdf) for the Tic T500, the DRV8834 datasheet (2MB pdf) for the Tic T834, the DRV8825 datasheet (1MB pdf) for the Tic T825, or the TB67S249FTG datasheet (533k pdf) for the Tic T249.

In STEP/DIR mode, the Tic’s USB, serial, and I²C interfaces can still be used to set the driver’s current limit, decay mode, and step mode, or to de-energize the driver.

Alternatively, when the Tic’s control mode is set to anything other than “STEP/DIR”, you can use the STEP and DIR pins as outputs to control an external stepper motor driver. However, you will still need to supply power to the Tic’s VIN pin, or else the Tic will report a “Low VIN” error and not attempt to drive the motor.

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