Issues with PWM and GPIOTE: interrupt masking and missing pulses

[sgabran]

Hi,

Problems I am having with PWM:

1. Using app_PWM and GPIOTE to start and stop the PWM: When button is pressed, GPIOTE handler sets a flag that is polled to start the PWM. PWM starts "app_pwm_enable(&PWM1);" and the GPIOTE does not responds to any other button presses. I tried to manioulate the IRQ priority for the GPIOTE but no good.

2. Using driver PWM or app_PWM to produce 4MHz pulses, starting with 8MHz or 16MHz clock, there are always missing pulses.

any advice ?

thanks

[Sigurd]

Hi,

I recommend using PWM driver for this.

Here is some example code on how to generate a defined number of 4 MHz pulses when a button on the DK is pressed.

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/** @file
 * @defgroup pwm_example_main main.c
 * @{
 * @ingroup pwm_example
 *
 * @brief PWM Example Application main file.
 *
 * This file contains the source code for a sample application using PWM.
 */

#include <stdio.h>
#include <string.h>
#include "nrf_drv_pwm.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "boards.h"
#include "bsp.h"
#include "app_timer.h"
#include "nrf_drv_clock.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);

#define PWM_PIN 3

#define TOP_VALUE 4

// Set to the number of pulses to be generated
#define PULSES 12

static void pwm_init(void)
{
    nrf_drv_pwm_config_t config =
    {
        // These are the common configuration options we use for all PWM
        // instances.
        .irq_priority = APP_IRQ_PRIORITY_HIGH,
        .count_mode   = NRF_PWM_MODE_UP,
        .step_mode    = NRF_PWM_STEP_AUTO,
    };

    config.base_clock = NRF_PWM_CLK_16MHz;
    config.top_value  = TOP_VALUE;
    config.load_mode  = NRF_PWM_LOAD_COMMON;

    config.output_pins[0] = PWM_PIN;
    config.output_pins[1] = NRF_DRV_PWM_PIN_NOT_USED;
    config.output_pins[2] = NRF_DRV_PWM_PIN_NOT_USED;
    config.output_pins[3] = NRF_DRV_PWM_PIN_NOT_USED;
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config, NULL));
}

static void generate_pulse_1mhz(uint16_t pulses)
{

    static uint16_t /*const*/ seq_values[] ={0,0x8000};
    
    nrf_pwm_sequence_t const seq =
    {
        .values.p_common = seq_values,
        .length          = NRF_PWM_VALUES_LENGTH(seq_values),
        .repeats         = 0,
        .end_delay       = 0
    };
    
    nrf_drv_pwm_simple_playback(&m_pwm0, &seq, pulses,  NRF_DRV_PWM_FLAG_STOP);

}
static void bsp_evt_handler(bsp_event_t evt)
{
    switch (evt)
    {
        
        case BSP_EVENT_KEY_0:
             generate_pulse_1mhz(PULSES);

             break;

       
       case BSP_EVENT_KEY_1:

                   break;
            
        default:
            return;
    }

}



void app_error_fault_handler(uint32_t id, uint32_t pc, uint32_t info)
{
    bsp_board_leds_on();
    app_error_save_and_stop(id, pc, info);
}

static void init_bsp()
{
    APP_ERROR_CHECK(nrf_drv_clock_init());
    nrf_drv_clock_lfclk_request(NULL);

    APP_ERROR_CHECK(app_timer_init());
    APP_ERROR_CHECK(bsp_init(BSP_INIT_BUTTONS, bsp_evt_handler));
    APP_ERROR_CHECK(bsp_buttons_enable());
}


int main(void)
{
    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();


    NRF_LOG_INFO("PWM example started.");
    init_bsp();

    bool accurate_HFCLK = true;

    if(accurate_HFCLK)
    {
      // Start accurate HFCLK (XOSC), will consume more current!
      NRF_CLOCK->TASKS_HFCLKSTART = 1;
      while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) ;
      NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
    }

    pwm_init();


    for (;;)
    {
        // Wait for an event.
        __WFE();

        // Clear the event register.
        __SEV();
        __WFE();

        NRF_LOG_FLUSH();
    }
}


/** @} */

 

[sgabran]

Thank you Sigurd, all the best