RE: Minimizing System Off current when using PWM

Mike Austin (LPI) — Tue, 06 May 2025 01:15:48 GMT

Thanks Vidar.

Turns out the issue wasn't to do with my pwm device, but the fact that I wasn't putting my stepper motor driver into its low current "sleep" mode prior to going into System OFF {face palm}

Anyway, I added the above step in my shutdown procedure anyway, as its probably good practise.

Best regards,

Mike

RE: Minimizing System Off current when using PWM

Vidar Berg — Mon, 05 May 2025 12:17:09 GMT

Hello Mike,

GPIO configurations are retained in System OFF mode, so an PWM output can continue to drive the output high or low in this state. Depending on what it is connected to, this may lead to excessive current draw. To stop the PWM and bring the GPIOs back to their default reset state, you can use the power management suspend task just before calling sys_poweroff().

In your prj.conf

...
CONFIG_PM_DEVICE=y

Add suspend task before sys_poweroff():

	...
	/* Disable PWM and reset GPIO configuration */
	err = pm_device_action_run(<pwm dev>, PM_DEVICE_ACTION_SUSPEND);
	if (err) {
		LOG_ERR("Could not suspend PWM (%d)\n", err);
	}
	
	sys_poweroff();

Best regards,

Vidar