Ble advertising and timer conflict

[Folny]

Hi

I would like to ask you for advice on how to solve my problem with Ble and the timer I have nRf52840 and I am trying to add a timer to examples\ble_peripheral\ble_app_uart timer works properly unless advertising_start(); and then the timer conflict with Ble begins. Does anyone have a solution to this problem ? I am adding part of the timer code and also photos where to see my problem.

#define GPIO_24       NRF_GPIO_PIN_MAP(0,24)

void timer_init(void)
{
    NRF_TIMER2->TASKS_STOP = 1;

    NRF_TIMER2->SHORTS    = (TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos);
    NRF_TIMER2->MODE      = TIMER_MODE_MODE_Timer;
    NRF_TIMER2->BITMODE   = (TIMER_BITMODE_BITMODE_24Bit << TIMER_BITMODE_BITMODE_Pos);
    NRF_TIMER2->PRESCALER = 1;  
    NRF_TIMER2->INTENSET  = (TIMER_INTENSET_COMPARE0_Set << TIMER_INTENSET_COMPARE0_Pos);

    NRF_TIMER2->CC[0]       = 100;

    NRF_TIMER2->TASKS_START = 1;
	NVIC_EnableIRQ(TIMER2_IRQn);
} 

void TIMER2_IRQHandler(void)
{
    if (NRF_TIMER2->EVENTS_COMPARE[0])
    {
       nrf_gpio_pin_toggle(GPIO_24);
	   NRF_TIMER2->EVENTS_COMPARE[0] = 0;
    }
}

not start advertising

start advertising

[haakonsh]

The SoftDevice has execution priority during timing-critical radio events. That means that your TIMER's ISR is blocked from executing during advertisements. 

If you need to toggle a GPIO based on a TIMER, you should use the PPI and GPIOTE peripherals. That way do not even need the TIMER interrupt at all.

[Folny]

Thank you for your answer but I don't want to switch only GPIO I need it to read and sample data with AD7691.

[haakonsh]

At what sample rate?
And for how long, continuously?

[Folny]

The frequency will be about 40-80 kHz and must run continuously.

Here is part of the code

int32_t AD7982_Read_GPIO(void){

  int16_t  AD_Data = 0;
  char BitCounts = 0;

  NRF_GPIO->OUTSET = (1UL << ADC_CNV_PIN);
  Delay_ADC(40);
  NRF_GPIO->OUTCLR = (1UL << ADC_CNV_PIN);
  Delay_ADC(10);
	
for(BitCounts = 0; BitCounts < 18; BitCounts++)
{
  AD_Data = AD_Data << 1;
	NRF_GPIO->OUTSET = (1UL << ADC_CLK_PIN);
  AD_Data |= nrf_gpio_pin_read(ADC_MISO_PIN);
  NRF_GPIO->OUTCLR = (1UL << ADC_CLK_PIN);
}
  return AD_Data;
}

void TIMER2_IRQHandler(void){

  if (NRF_TIMER2->EVENTS_COMPARE[0]){
			
  ctr++;
  ticks++;
	
  int32_t AD_Read = AD7982_Read_GPIO();
  bins[ctr] = AD_Read;
	
  if (ctr == SAMPLES -1)
  {
    ++numSamples;
    if (numSamples == numSamplesToAverage)
    {
      numSamples = 0;
      if (!sampleReady)     
      {
        memcpy((void*)averages, bins, sizeof(averages));
        sampleReady = true;
      }
      memset(bins, 0, sizeof(bins));
    }
		ctr = -1;
   } 
    NRF_TIMER2->EVENTS_COMPARE[0] = 0;
  }
}

[Folny]

The code will be based on this principle but an external 18bit ADC AD7691 will be used.

https://github.com/dc42/arduino/blob/master/MetalDetector/MetalDetector.ino

[haakonsh]

Then you have three options:

1. Not use the SoftDevice.
   If all you're going to do with BLE is to send periodic advertisements then you don't really need the SoftDevice, you can control the RADIO directly and send advertisements when you have available CPU time. 
   
   
2. Use the PPI peripheral to create a state-machine that runs independently from the CPU, with the purpose of controlling the ADC.
   
   
3. Use the SAADC peripheral instead. It has Direct Memory Access through EasyDMA, this means that you can run the SAADC independently from the CPU. 

[Folny]

I was considering using an esb library so it would work well but I want the device to work via bluetooth with a mobile phone so the only option is to send ads manually. So my question is, what command should I use in the code to send the ad ?.

[haakonsh]

Well, what are your goals here?
What information are you sending over BLE?
Why do you need the external adc? What signals are you sampling?

[Folny]

Ble I want to use as a classic uart and send data to the phone's external ADC is because I need to measure very small differences in values. I am also attaching the file I want to edit for my project, timer 2 has been added there and it is created in nRF5_SDK_16.0.0 please try to look at it and edit it to make the timer stable I will be very grateful to you.

4572.ble_app_uart.zip

[haakonsh]

Do you intend to stream the adc data to the phone?

Also, you need a driver-amplifier for the AD7691 anyways, so why don't you just use a regular instrumental amplifier and the internal SAADC of the nRF52? 

There's little chance that you will be able to have a continuous sampling of the external ADC with concurrent BLE operation, it will require significant development time.

[Folny]

Yes I want to send data to the phone I wanted to use a quality ADC so I decided to use AD7691 but with that is not a problem my project is already done and the PCB designed and installed when I designed the PCB I had no idea there would be problems with the timer.