Precise angle control of Servo motor using PWM

RE: Precise angle control of Servo motor using PWM

ovrebekk — Thu, 29 Jul 2021 08:03:49 GMT

Good to hear you figured it out. I will consider the case resolved then 🙂

RE: Precise angle control of Servo motor using PWM

Salman — Wed, 28 Jul 2021 04:55:03 GMT

I figured it out nrfx_pwm_stop(&m_pwm0, true); will make it stop and when every I want to move the servo I can just use the pwm_update_duty_cycles and it will work.

RE: Precise angle control of Servo motor using PWM

Salman — Wed, 28 Jul 2021 04:42:51 GMT

How can I enable and disable the PWM instance? I only want to enable it when I want to use it. It was possible using PWM library is it possible using PWM driver?

RE: Precise angle control of Servo motor using PWM

Salman — Wed, 28 Jul 2021 04:27:26 GMT

I figured it out I have to enable the PWM legacy layer in the sdk_config as well

RE: Precise angle control of Servo motor using PWM

Salman — Tue, 27 Jul 2021 21:09:06 GMT

Thanks for the code. With some modification the example you have given is working. However when I am trying to implement it in "ble_app_uart" example I am getting the following error.

..\..\..\main.c(96): error: #20: identifier "NRFX_PWM0_INST_IDX" is undefined

I have enabled the following in the sdk_config.h

here NRFX_PWM0_INST_IDX is disabled, however I have enabled it in the sdk_config.h (as shown in the picture above.)

I am unable to figure out what is the problem.

RE: Precise angle control of Servo motor using PWM

ovrebekk — Mon, 26 Jul 2021 13:51:20 GMT

I wouldn't recommend using the app_pwm driver unless you are targetting the nRF51 series. The nRF51 lacked a proper PWM controller, and the app_pwm library was developed to mitigate this.

On the nRF52 series I recommend using the nrf_drv_pwm driver instead, which uses the PWM module in the device rather than relying on timers.

I made a small example some while back showing how to use the nrf_drv_pwm driver to set 4 outputs in a loop:

devzone.nordicsemi.com/.../6644.pwm_5F00_driver_5F00_simple.zip

The resolution of the PWM in your case depends primarily on the clock speed, which is set to 1MHz in the example but can be configured up to 16MHz if needed.

If you keep the frequency at 1MHz and set the countertop value to 20000 you should have a total PWM interval of 20ms, and a total of 1000 values to choose from when adjusting the PWM length between 1ms and 2ms.

Best regards
Torbjørn