Generate PWM frequency smaller than 4Hz.

RE: Generate PWM frequency smaller than 4Hz.

Kenneth — Thu, 23 Jan 2025 15:38:25 GMT

The hardware does not support this low frequency.

The zephyr driver unfortunately doesn’t iterate through all possible software PWM nodes in the device tree and just works off of the 0th one.

https://github.com/zephyrproject-rtos/zephyr/blob/e60da1bd640a37370870a83277142dd560f1fb8d/drivers/pwm/pwm_nrf_sw.c#L428

Kenneth

RE: Generate PWM frequency smaller than 4Hz.

SnaiderBG — Tue, 21 Jan 2025 16:50:44 GMT

With the sw_pwm, we are having issues mainly with the device tree, it works for the predefined node pwm_led0 but when we try to use another it doesn't work. In the case we use the nrfx_pwm what considerations should we have, with the device tree and configurations. Can we still use other pwms with the zephyr pwm API?

RE: Generate PWM frequency smaller than 4Hz.

Susheel Nuguru — Tue, 21 Jan 2025 11:56:46 GMT

Have not tried this myself with sw_pwm, but what is the the error you are getting if you try to do this for 2 custom outputs? I am assuming that you have it working to get 1 Hz for 1 custom output?

Maybe use of nrfx_pwm API can be give you more control on configurations of what prescalar you want to put for timing?