sdk11 pwm frequency control

RE: sdk11 pwm frequency control

Stefan Birnir Sverrisson — Tue, 30 Aug 2016 16:55:35 GMT

ok, I see your point.

To get 38.0 kHz, I suspect you need timer prescaler as = 0 to have the base frequency of the timer as 16MHz

The desired timer ticks are therefore 16MHz/38khz=421=0x1A5. In order to set the TIMER CC value as 0x1A5, you could hardcode that in the app_pwm.c -> app_pwm_init function. Instead of calling nrf_drv_timer_us_to_ticksin line 777, just set ticks = 0x1A5;

RE: sdk11 pwm frequency control

HakJae — Tue, 30 Aug 2016 06:56:01 GMT

So i used "app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_2CH(26L, 3, BSP_LED_1);" and "app_pwm_channel_duty_set(&PWM1, 0, 50);". it can control period merely 'us' unit. it have 38.461khz.. i want to have 38.0xx khz. So i should control prescaler. how to control prescaler ?

RE: sdk11 pwm frequency control

Stefan Birnir Sverrisson — Tue, 30 Aug 2016 06:29:08 GMT

For reliable PWM, use the PWM library in SDK 11. The PWM library uses TIMER peripheral in the background. There is a library function app_pwm_channel_duty_set to set the duty cycle. To set the PWM period, configure app_pwm_config_t.period_us before initializing the PWM library. There is pwm_library example in SDK 11.