Servomotor

Overview

This is a sample app which drives a servomotor using the PWM API.

The sample rotates a servomotor back and forth in the 180 degree range with a PWM control signal.

This app is targeted for servomotor ROB-09065. The corresponding PWM pulse widths for a 0 to 180 degree range are 700 to 2300 microseconds, respectively. Different servomotors may require different PWM pulse widths, and you may need to modify the source code if you are using a different servomotor.

Requirements

The sample requires a servomotor whose signal pin is connected to a pin driven by PWM. The servo must be defined in Devicetree using the pwm-servo compatible (part of the sample) and setting its node label to servo. You will need to do something like this:

/ {
    servo: servo {
        compatible = "pwm-servo";
        pwms = <&pwm0 1 PWM_MSEC(20) PWM_POLARITY_NORMAL>;
        min-pulse = <PWM_USEC(700)>;
        max-pulse = <PWM_USEC(2500)>;
    };
};

Note that a commonly used period value is 20 ms. See samples/basic/servo_motor/boards/bbc_microbit.overlay for an example.

Wiring

BBC micro:bit

You will need to connect the motor’s red wire to external 5V, the black wire to ground and the white wire to the SCL pin, i.e. pin P19 on the edge connector.

Building and Running

The sample has a devicetree overlay for the BBC MicroBit.

This sample can be built for multiple boards, in this example we will build it for the bbc_microbit board:

west build -b bbc_microbit samples/basic/servo_motor
west flash