NRF51 Flash write during brown-out

RE: NRF51 Flash write during brown-out

butch — Sat, 03 Jun 2017 21:45:45 GMT

Another thread says 2.3V is adequate for flash write to work. Can I assume that EVENTS_POFWARN is wired to the internal circuitry that disables the NVMC? If so, then if, in the ISR you clear EVENTS_POFWARN (set at 2.7V) after determining it is set but before attempting write to flash, the write might succeed? My goal is, in a browning out system, to write the PC to UICR (not to program flash.) I don't need the memory protection, I need to know where in the code it is browning out, while debugging a system that intends to manage power from a weak solar powered supply. (sans SD.) I might post this as a separate question.

RE: NRF51 Flash write during brown-out

Susheel Nuguru — Thu, 09 Jul 2015 13:00:18 GMT

I have Agilent variable DC output power supply www.tequipment.net/.../

RE: NRF51 Flash write during brown-out

Bouke — Thu, 09 Jul 2015 12:56:45 GMT

Thanks for the thorough answer! How did you change the input power?

RE: NRF51 Flash write during brown-out

Susheel Nuguru — Wed, 08 Jul 2015 13:24:25 GMT

pin 22 is connected to LED and it does not change its state. if I move the write operation into main just before the check, then it sucesfully writes and the LED changes its state. So the conclusion is that after the POFWARN event occured, write failed. write block is removed if your voltage is again above the POF threshold.

RE: NRF51 Flash write during brown-out

Susheel Nuguru — Wed, 08 Jul 2015 13:21:38 GMT

This threshold is user set and you have to enable Power Fail comparator function explicitly . Please look into Power_Register ->POFCON

Regarding you write operation, all writes are blocked immediately after EVENTS_POFWARN is triggered. I verified this on 100028 board

#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "nrf_gpio.h"
#include "boards.h"

#define POF_PIN      (21)

void soc_hal_flash_word_unprotected_write(uint32_t * p_address, uint32_t value)
{
  NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos);
  while (NRF_NVMC->READY == NVMC_READY_READY_Busy)
  {
    // Do nothing.
  }
  *p_address = value;

  // Wait flash write to finish
  while (NRF_NVMC->READY == NVMC_READY_READY_Busy)
  {
      // Do nothing.
  }

  // Turn off flash write enable and wait until the NVMC is ready.
  NRF_NVMC->CONFIG = (NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos);
  while (NRF_NVMC->READY == NVMC_READY_READY_Busy)
  {
    // Do nothing.
  }
}

uint32_t *ptr = (uint32_t *)0X3C000;
void POWER_CLOCK_IRQHandler()
{
    if(NRF_POWER->EVENTS_POFWARN == 1)
    {
        soc_hal_flash_word_unprotected_write(ptr, 0XDEADBEEF);
        NRF_POWER->EVENTS_POFWARN = 0;
        nrf_gpio_pin_toggle(POF_PIN);
        
    }
}

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    // Configure LED-pins as outputs.
    LEDS_CONFIGURE(1<<POF_PIN);
    LEDS_CONFIGURE(1<<22);
    nrf_gpio_pin_clear(POF_PIN);
    nrf_gpio_pin_clear(22);
    NRF_POWER->INTENSET = POWER_INTENSET_POFWARN_Msk;
    NRF_POWER->POFCON = ((POWER_POFCON_THRESHOLD_V23 << POWER_POFCON_THRESHOLD_Pos) | (POWER_POFCON_POF_Enabled << POWER_POFCON_POF_Pos));
    NVIC_EnableIRQ(POWER_CLOCK_IRQn);
    while(1)
    {
    if(*ptr == 0XDEADBEEF)
    {
        nrf_gpio_pin_set(22);
    }
    };
    
}