How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

RAM_MS — Mon, 20 Sep 2021 11:56:05 GMT

I want One-pulse mode PWM like present in stm32 .

50% duty cycle is fine and 1Mhz i.e 1 microsecond clock .

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

Kenneth — Mon, 20 Sep 2021 07:38:11 GMT

I thought you wanted 50% duty cycle, if you want different duty cycle then maybe you can consider using a second pwm instance for the second channel? If you start them from the CPU there will be a 16MHz period between the two, will that be a problem?

Kenneth

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

RAM_MS — Fri, 17 Sep 2021 06:44:30 GMT

Hello

Again by doing (duty | 0x8000) channel 1 output is opposite to channel 0 but with different duty cycle .

That is if duty cycle of channel 0 is 40 then duty cycle become 60 .which is not required .

My question was about opposite polarity with same duty cycle.

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

RAM_MS — Thu, 16 Sep 2021 13:09:28 GMT

Hello ,Kenneth

Please guide me to solve this problem .

My simple aim to control two pwm channel in opposite duty cycle from interrupt and interrupt signal is also an square wave signal with 50% duty cycle and 20ms period.

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

Kenneth — Thu, 16 Sep 2021 12:22:20 GMT

Please don't mix direct hardware access to the PWM peripheral and at the same time also use the driver to access the PWM peripheral. Then you very likely will end up in a bad state or configuration.

Kenneth

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

RAM_MS — Thu, 16 Sep 2021 11:12:30 GMT

Hello, Kenneth

I tried using pwm hardware peripheral but It's not working can You please guide me where is the fault in my code??

#define OUTPUT_PIN LED_1
#define OUTPUT_PIN2 LED_2

#define    PIN_IN    22
#define    PWM_PIN   11


unsigned int duty = 4000 ;
static volatile bool  gpio_flag;
  

static int16_t buf[] = {10000}; // Inverse polarity (bit 15), 10000us duty cycle
static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);



// Declare variables holding PWM sequence values. In this example only one channel is used 
nrf_pwm_values_individual_t seq_values[] = {0, 0, 0, 0};
nrf_pwm_sequence_t const seq =
{
    .values.p_individual = seq_values,
    .length          = NRF_PWM_VALUES_LENGTH(seq_values),
    .repeats         = 0,
    .end_delay       = 0
};

void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
   gpio_flag = true;
}

static void gpio_init(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_LOTOHI(true);
    in_config.pull = NRF_GPIO_PIN_PULLDOWN;

    err_code = nrf_drv_gpiote_in_init(PIN_IN, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_in_event_enable(PIN_IN, true);
}



// Set duty cycle between 0 and 100%
void pwm_update_duty_cycle(uint16_t duty_cycle)
{
    
   
    {
        seq_values->channel_0 = duty_cycle ;
        seq_values->channel_1 = duty_cycle | 0x8000;
    }
    
    
    nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}

static void pwm_init(void)
{
    nrf_drv_pwm_config_t const config0 =
    {
        .output_pins =
        {
            OUTPUT_PIN, // channel 0
            OUTPUT_PIN2,             // 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_1MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 10000,
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    // Init PWM without error handler
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config0, NULL));
    
}

static void zcd_init(void)
{

 // Configure PWM_PIN as output, and set it to 0
  NRF_GPIO->DIRSET = (1 << PWM_PIN);
  NRF_GPIO->OUTCLR = (1 << PWM_PIN);
  
  
  NRF_PWM0->PRESCALER   = PWM_PRESCALER_PRESCALER_DIV_16; // 1 us
  NRF_PWM0->PSEL.OUT[0] = PWM_PIN;
  NRF_PWM0->MODE        = (PWM_MODE_UPDOWN_Up << PWM_MODE_UPDOWN_Pos);
  NRF_PWM0->DECODER     = (PWM_DECODER_LOAD_Individual       << PWM_DECODER_LOAD_Pos) | 
                          (PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos);
  NRF_PWM0->LOOP        = (PWM_LOOP_CNT_Disabled << PWM_LOOP_CNT_Pos);
  
  NRF_PWM0->COUNTERTOP = 20000; // 20ms period
  
  
  NRF_PWM0->SEQ[0].CNT = ((sizeof(buf) / sizeof(uint16_t)) << PWM_SEQ_CNT_CNT_Pos);
  NRF_PWM0->SEQ[0].ENDDELAY = 0;
  NRF_PWM0->SEQ[0].PTR = (uint32_t)&buf[0];
  NRF_PWM0->SEQ[0].REFRESH = 0;
  NRF_PWM0->SHORTS = 0;
  
  NRF_PWM0->ENABLE = 1;
  NRF_PWM0->TASKS_SEQSTART[0] = 1;
}

int main(void)
{

  // Start accurate HFCLK (XOSC)
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) ;
  NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
   
    bsp_board_init(BSP_INIT_LEDS);
    zcd_init();
    gpio_init();
    pwm_init();
    gpio_flag = false;
    

    while (1)
    {
        //if (gpio_flag == true)
        {
          gpio_flag = false;
          unsigned int val = duty;
          pwm_update_duty_cycle(val);
        }
    }
}

Mainly my zcd_init() function is not working . where I created an 50% duty cycle signal of 20 ms period and given to my gpio interrupt pin 22.

RE: How to set duty cycle of two pwm channel in opposite polarity inside gpio interrupt handler?

Kenneth — Tue, 07 Sep 2021 13:22:23 GMT

Hi,

I notice you are using app_pwm, which is not actually the PWM hardware peripheral instance, but instead app_pwm is using several ppi, gpiote and timer to create a PWM signal:
https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.2/lib_pwm.html

You may get into trouble updating the PWM in such case since it will depend on the interrupt priority of those peripherals.

I instead suggest that you use the PWM hardware peripheral, which have no such dependencies.

You can find an example here that show how you can setup the PWM peripheral:
https://devzone.nordicsemi.com/f/nordic-q-a/39314/pwm-update_function/152602#152602

You can find an example below where pwm channel 1 is inverted of pwm channel 0:

/cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-e7e4528908a64f45bf120ad5a23ef4b4/25464.main.c

The above main.c is a modification of \nRF5_SDK_17.0.2_d674dde\examples\peripheral\pwm_driver