RE: Synchronized PWM outputs with nRF Connect SDK

DougR — Sat, 27 Jan 2024 22:32:56 GMT

I got it working. Looks like pwm_set_dt() only sets the first channel. The following code sets each channel individually, and seems to work as desired.

#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>
#include <zephyr/device.h>
#include <zephyr/drivers/pwm.h>
#include <math.h>

static const struct pwm_dt_spec custompwm0 = PWM_DT_SPEC_GET(DT_ALIAS(mycustompwm));

#define PWM_FREQ 100 // Hz
#define CYCLE_FREQ 1 // Hz

#define STEPS 8
float levels[STEPS]; 
#define DUTY_RANGE 0.8f
#define DEADTIME_NS 500U

#define TWO_PI 6.28318530718f

int main(void)
{
	int ret;

	if (!device_is_ready(custompwm0.dev)) {
		printk("Error: PWM device %s is not ready\n",
		       custompwm0.dev->name);
		return 0;
	}

	for (int i =0; i < STEPS; i++) {
		levels[i] = 0.5f*(1 + DUTY_RANGE*sin(TWO_PI*i/STEPS));
	}

	int count = 0;
	
	while (1) {
		ret = pwm_set_dt(&custompwm0, 
			PWM_HZ(PWM_FREQ), 
			(int) PWM_HZ(PWM_FREQ)*levels[count++ % STEPS]);
		ret = pwm_set(custompwm0.dev, 1,
			PWM_HZ(PWM_FREQ), 
			(unsigned int) PWM_HZ(PWM_FREQ)*levels[count % STEPS] - DEADTIME_NS, PWM_POLARITY_NORMAL);
		ret = pwm_set(custompwm0.dev, 2,
			PWM_HZ(PWM_FREQ), 
			(unsigned int) PWM_HZ(PWM_FREQ)*levels[count % STEPS] + DEADTIME_NS, PWM_POLARITY_INVERTED);

		if (ret) {
			printk("Error %d: failed to set pulse width\n", ret);
			return 0;
		}

		k_sleep(K_USEC(1000000U/(CYCLE_FREQ*STEPS)));
	}
	return 0;
}