Step/Direction

This is the simplest possible way of controlling the ODrive. It is also the most primitive and fragile one. So don’t use it unless you must interoperate with other hardware that you don’t control.

Pinout

While any GPIOs can be used, we suggest using the Isolated IO pins STEP and DIR, please refer to the pinout page to locate these pins on your ODrive.

Important

ISO_VDD and ISO_GND must be provided by the microcontroller to use these Isolated IO pins.

To use alternative GPIO pins for this interface, set <axis>.config.step_gpio_pin and <axis>.config.dir_gpio_pin to their desired GPIO number and save_configuration().

How to Configure

  1. Set the STEP gpio (S) mode to DIGITAL_PULL_DOWN:

    <odrv>.config.gpio(S)_mode = GpioMode.DIGITAL_PULL_DOWN

  2. Set the DIR gpio (D) mode to DIGITAL:

    <odrv>.config.gpio(D)_mode = GpioMode.DIGITAL

  3. Enable the interface:

  4. Enable circular setpoints

    <axis>.controller.config.circular_setpoints = True
<axis>.pos_vel_mapper.config.circular_setpoints = True

After this, step and direction will be enabled when you put the axis into closed loop control. Note that to change out of step/dir, you need to set <axis>.config.enable_step_dir to False, go to AxisState.IDLE, and then back into closed loop control.

Circular setpoints are used to keep floating point error at a manageable error for systems where the motor can rotate large amounts. If the motor is commanded out of the circular range, the position setpoint automatically wraps around to stay in the range. Two parameters are used to control this behavior: <odrv>.<axis>.controller.config.circular_setpoint_range and <odrv>.<axis>.controller.config.steps_per_circular_range. The circular setpoint range sets the operating range of input_pos, starting at 0.0. The steps per circular range setting controls how many steps are needed to traverse the entire range.

For example, to use 1024 steps per 1 motor turn, in a space that wraps every 128 turns:

<axis>.controller.config.circular_setpoint_range = 128.0      #[turns]
<axis>.pos_vel_mapper.config.circular_setpoint_range = 128.0      #[turns]
<axis>.controller.config.steps_per_circular_range = 1024*128 #[steps]

The circular range is a floating point value and the steps per circular range parameter is an integer. For best results, set both parameters to powers of 2.

The maximum step rate is pending tests, but 250kHz step rates with both axes in closed loop has been achieved.

Please be aware that there is no enable line right now, and the step/direction interface is enabled by default, and remains active as long as the ODrive is in position control mode. To get the ODrive to go into position control mode at bootup, see how to configure the startup procedure.