#nrf52840: create 2 PWMs with different pulse width using single instance by direct register access

[vikrant8051]

As per #nrf52840 datasheet

  NRF_P0->DIR |= 0x0001E000;
  NRF_P0->OUT |= 0x0001E000;


  uint16_t pwm_seq[4]= {160 , 3200};

  NRF_PWM0->PSEL.OUT[0] = 0;
  NRF_PWM0->PSEL.OUT[0] = 13 ;

  NRF_PWM0->PSEL.OUT[1] = 0 ;
  NRF_PWM0->PSEL.OUT[1] = 14 ;

  NRF_PWM0->ENABLE = 0x00000001;
 
  NRF_PWM0->MODE = 0x00000000;

  NRF_PWM0->PRESCALER = 0x00000000; //16Mhz

  NRF_PWM0->COUNTERTOP = 16000; // PWM_Freq = 1000 Hz

  //NRF_PWM0->LOOP = 0x00000000;

  //NRF_PWM0->DECODER = 0x00000002;
 
  NRF_PWM0->SEQ[0].PTR = (uint32_t)(pwm_seq);
 
  NRF_PWM0->SEQ[0].CNT = 2;
 
  NRF_PWM0->SEQ[0].REFRESH = 0;
 
  NRF_PWM0->SEQ[0].ENDDELAY = 0;
 
  NRF_PWM0->TASKS_SEQSTART[0] = 1;

I've configured PWM0 registers as mentioned above. But with this setting both LED1 & LED2 are showing same intensity that means both channels set to common pulse width.

How to edit this configuration so that both channels will set to different pulse width ?

If I set NRF_PWM0->DECODER = 0x00000002; I didn't observe anything on two channels.

How to update pulse width dynamically after these initial configuration ?

Thank You !!

[vikrant8051]

Hello World !!

Here answering my own question....

I found that working of PWM module depends upon sequence of configuration.

Here is simple working demo,

//---------------------------------------------------------------------------------------------------------------------------------------------------------

#include "nrf_delay.h"

uint16_t pwm_seq[4];

void gpio_init(void)
{

  NRF_P0->DIR |= 0x0001E000;   
  NRF_P0->OUT |= 0x0001E000; 

  NRF_PWM0->PSEL.OUT[0] = 13 ;     // LED_1
  NRF_PWM0->PSEL.OUT[1] = 14 ;     // LED_2
 
  NRF_PWM0->MODE = 0x00000000;

  NRF_PWM0->PRESCALER = 0x00000004; //1 Mhz

  NRF_PWM0->COUNTERTOP = 1000;  //1 Khz

  NRF_PWM0->DECODER = 0x00000002;
 
  NRF_PWM0->LOOP = 0x00000000;
 
  NRF_PWM0->SEQ[0].REFRESH = 0;
 
  NRF_PWM0->SEQ[0].ENDDELAY = 0;

  NRF_PWM0->SEQ[0].PTR = (uint32_t)(pwm_seq);
 
  NRF_PWM0->SEQ[0].CNT = 4;

  NRF_PWM0->ENABLE = 0x00000001;
 
  NRF_PWM0->TASKS_SEQSTART[0] = 1;


}


int main(void)
{
 
  unsigned char data=0;
  int i;

  gpio_init();

  while(1)
  {
    pwm_seq[0] += 10;
    pwm_seq[1] += 100;
    
    NRF_PWM0->TASKS_SEQSTART[0] = 1;

    if(pwm_seq[0] > 1000)
    {
      pwm_seq[0] = 0;
    }

    if(pwm_seq[1] > 1000)
    {
      pwm_seq[1] = 0;
    }


    nrf_delay_ms(100);
 
  }

  return(0);

}