nrf52832 pwm interrupt at end of period

[L.B.]

Hello everyone,

I'm trying to make a PWM signal that fires an interrupt at the end of each PWM period. I've had the same question here:

https://devzone.nordicsemi.com/f/nordic-q-a/45182/nordic-nrf51822-pwm-ppi-timer1

but now I'm using nrf52832.

Is it possible to have such an interrupt?

If yes, can I do it with nrf_drv_ APIs instead of direct register access like in the link above?

Regards,

L. B.

[haakonsh]

You'll have to port the code to use the Timer driver API's. Afterwards, what you need to do to enable the interrupt is to call nrf_drv_timer_compare_int_enable(). The event handler provided to nrf_drv_timer_init will be called on any interrupt generated by that timer instance, so you'll have to determine what event it was, see:

nrf_drv_timer_init, nrf_timer_event_handler_t, and nrf_timer_event_t. 

[L.B.]

OK, so there is no legal way to do it, because the event NRF_PWM_EVENT_PWMPERIODEND is not being used by the driver.

Here is how I did it, with combined approach driver API + register access:

#include "nrf_drv_pwm.h"
#include "nrfx_pwm.h"

static nrf_drv_pwm_t m_pwm1 = NRF_DRV_PWM_INSTANCE(1);

static nrf_drv_pwm_config_t config1 = {
        .output_pins = {
                3, // channel 0
                NRF_DRV_PWM_PIN_NOT_USED, // channel 1
                NRF_DRV_PWM_PIN_NOT_USED, // channel 2
                NRF_DRV_PWM_PIN_NOT_USED  // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_16MHz,
        .count_mode   = NRF_PWM_MODE_UP_AND_DOWN,
        .top_value    = 116, //~70kHz
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
};

static nrf_pwm_values_individual_t /*const*/ seq_values[] = {
        {0x4D}
};

static nrf_pwm_sequence_t const pwm_seq_settings = {
        .values.p_individual = seq_values,
        .length              = NRF_PWM_VALUES_LENGTH(seq_values),
        .repeats             = 0,
        .end_delay           = 0
};

void user_touch_pwm_handler(nrf_drv_pwm_evt_type_t event_type){
    static uint32_t count = 0;

    if(count == 9){
        nrf_drv_pwm_uninit(&m_pwm1);
    }

    count++;
}

void user_touch_pwm_init(void){
    nrf_drv_pwm_init(&m_pwm1, &config1, user_touch_pwm_handler);
    m_pwm1.p_registers->INTENSET |= NRF_PWM_INT_PWMPERIODEND_MASK;
    nrf_drv_pwm_simple_playback(&m_pwm1, &pwm_seq_settings, 1, NRF_DRV_PWM_FLAG_LOOP);
}

This program will generate 10 pulses on P0.03 with 70 kHz frequency and will stop.

Regards,

L. B.