Writing data to Central (BLEserial example) at set interval with timer.

Question

Hello Everyone,

I newbie to BLE world and new to programming. Currently I am following this github repo: https://github.com/sandeepmistry/arduino-BLEPeripheral . I am using nrf51822, S130 SDK11 with arduino 1.8.1.
I am trying to write data (battery data) and toggle led at set interval using timer 2.
I am using BLESerial example code to write data.
When the timer times out, the BLE kind of crashes and doesn't respond
However, if I disable "BLESerial.write(data);" , the led toggles properly and program runs correctly.
Somehow, the BLESerial call is causing problem. Is it something that BLESerial function calls and TIMER2 are inter-related?
I checked the product specification which mentions TIMER0 is used by softdevice and there is no dependency on TIMER2. Can someone help me out for this issue?

Timer code:
void ms_timer_init(void)
{
    
    NRF_TIMER2->TASKS_STOP        = 1;                       // Stop timer, if it was running
    NRF_TIMER2->TASKS_CLEAR       = 1;
    NRF_TIMER2->MODE              = TIMER_MODE_MODE_Timer;   // Timer mode (not counter)
    NRF_TIMER2->EVENTS_COMPARE[0] = 0;                       // clean up possible old events
    NRF_TIMER2->EVENTS_COMPARE[1] = 0;
    NRF_TIMER2->EVENTS_COMPARE[2] = 0;
    NRF_TIMER2->EVENTS_COMPARE[3] = 0;

    // Timer is polled, but enable the compare0 interrupt in order to wakeup from CPU sleep
    NRF_TIMER2->INTENSET    = TIMER_INTENSET_COMPARE0_Msk;
    NRF_TIMER2->SHORTS      = 1 << TIMER_SHORTS_COMPARE0_CLEAR_Pos;    // Clear the count every time timer reaches the CCREG0 count
    NRF_TIMER2->PRESCALER   = 9;                                       // Input clock is 16MHz, timer clock = 2 ^ prescale -> interval 1us
    NRF_TIMER2->CC[0]       = 32;                          // 625uS with 1MHz clock to the timer
    NVIC_EnableIRQ(TIMER2_IRQn);
    NRF_TIMER2->TASKS_START = 1;
}

// Start the timer - it will be running continuously}
/** TIMTER2 peripheral interrupt handler. This interrupt handler is called whenever there it a TIMER2 interrupt*/


void TIMER2_IRQHandler(void)
{
  if ((NRF_TIMER2->EVENTS_COMPARE[0] != 0) && ((NRF_TIMER2->INTENSET & TIMER_INTENSET_COMPARE0_Msk) != 0))
  { 
    NRF_TIMER2->EVENTS_COMPARE[0] = 0;         //Clear compare register 0 event
    BLESerial.write(data);
    digitalWrite(LED, !(digitalRead(LED)));
  }
}

ovrebekk · Accepted Answer

Hi 
 Most likely the issue is cased by running BLE functions from a high priority interrupt. When using a BLE stack such as the S130 SoftDevice interrupt priorities 0 and 2 are reserved for the SoftDevice, and should not be used by the application. 
 Try setting the interrupt priority of the TIMER2 interrupt to 3, and it should work better: 
 NVIC_SetPriority(TIMER2_IRQn, 3); 
 Best regards Torbjørn

Writing data to Central (BLEserial example) at set interval with timer.

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