gpio | Micro-RDK

gpio

The gpio model supports DC motors (both brushed and brushless).

You can configure encoders to work with gpio motors. Find more information in the encoded motor documentation.

To configure a DC motor as a component of your machine, first make sure the motor is wired to a suitable motor driver, which is in turn wired to the microcontroller. Configure the board to which the motor driver is wired. Then add your motor:

{
  "components": [
    {
      "name": "<your-board-name>",
      "model": "<your-board-model>",
      "api": "rdk:component:board",
      "attributes": {},
      "depends_on": [],
    },
    {
      "name": "<your-motor-name>",
      "model": "gpio",
      "api": "rdk:component:motor",
      "attributes": {
        "pins": {
          "dir": "<int>",
          "pwm": "<int>"
        },
        "board": "<your-board-name>",
        "min_power_pct": <float>,
        "max_power_pct": <float>,
        "pwm_freq": <float>,
        "dir_flip": <float>
      },
      "depends_on": []
    }
  ]
}

An example configuration for a gpio motor:

{
  "components": [
    {
      "name": "local",
      "model": "pi",
      "api": "rdk:component:board",
      "attributes": {},
      "depends_on": []
    },
    {
      "name": "example-gpio",
      "model": "gpio",
      "api": "rdk:component:motor",
      "attributes": {
        "pins": {
          "dir": "36",
          "pwm": "32"
        },
        "board": "local"
      },
      "depends_on": []
    }
  ]
}

The following attributes are available for gpio motors:

Name	Type	Required?	Description
`board`	string	Required	`name` of the board to which the motor driver is wired.
`pins`	object	Required	A structure that holds pin configuration information; see below.
`min_power_pct`	float	Optional	Sets a limit on minimum power percentage sent to the motor. Default: `0.0`
`max_power_pct`	float	Optional	Range is 0.06 to 1.0; sets a limit on maximum power percentage sent to the motor. Default: `1.0`
`pwm_freq`	int	Optional	Sets the PWM pulse frequency in Hz. Many motors operate optimally in the kHz range. Default: `800`
`dir_flip`	bool	Optional	Flips the direction of “forward” versus “backward” rotation. Default: `false`
`encoder`	string	Optional	The name of an encoder attached to this motor. See encoded motor.

Refer to your motor and motor driver data sheets for specifics.

`pins`

There are three common ways for your computer to communicate with a brushed DC motor driver chip. Your motor driver data sheet will specify which one to use.

PWM/DIR: Use this if one of your motor driver’s pins (labeled “PWM”) takes a pulse width modulation (PWM) signal to the driver to control speed while another pin labeled “DIR” takes a high or low signal to control the direction.
- Configure pwm and dir.
In1/In2: Use this if your motor driver has pins labeled “IN1” and “IN2” or “A” and “B,” or similar. One digital signal set to a high voltage and another set to a low voltage turns the motor in one direction and vice versa. Speed is controlled with PWM through one or both pins.
- Configure a and b.
In1/In2 and PWM: Use this if your motor driver uses three pins: In1 (A) and In2 (B) to control direction and a separate PWM pin to control speed.
- Configure a, b, and pwm.

Inside the pins struct you need to configure two or three of the following depending on your motor driver:

Name	Type	Required?	Description
`a`	string	Required for some drivers	Board pin number this motor driver’s “IN1” or “A” pin is wired to.
`b`	string	Required for some drivers	Board pin number this motor driver’s “IN2” or “B” pin is wired to.
`dir`	string	Required for some drivers	Board pin number this motor driver’s direction (“DIR”) pin is wired to.
`pwm`	string	Required	Board pin number this motor driver’s “PWM” pin is wired to.

PWM frequency and `esp32` boards

Each gpio motor uses a PWM pin at 10000 Hz PWM frequency.

This leaves you with three remaining PWM frequencies for use on an esp32. If the frequency of another PWM signal is unimportant, it can also be set to 10000 Hz. See PWM signals on esp32 pins for more information.

gpio

pins

PWM frequency and esp32 boards

`pins`

PWM frequency and `esp32` boards