Nrf52 simple Baremetal timer function, CPU reset if interrupt enabled.

[Abir Hossain]

Trying to use the basic baremetal mode as my application is very simple and dont want to go through RTOS stuff.

I tried with Timer and RTC, both case if I enable the interrupt then the cpu gets rebooted.
Following is the code, not sure if it is the way I am building the code or some other parameter is messing things up.

This example if basically "..\..\sdk\nRF5_SDK_17.1.0_ddde560\examples\peripheral\timer"
I will try to upload the zip of the full project. Different peripheral works except the Interrupt part.

#include <stdio.h>
#include <nrf.h>

#define PIN_LED1 (17UL) // nrf52-dk
volatile bool bLED1Set= false;
int main(void)
{
// Start LFCLK (32kHz) crystal oscillator. If you don't have crystal on your board, choose RCOSC instead.
NRF_CLOCK->LFCLKSRC = CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos;
NRF_CLOCK->TASKS_LFCLKSTART = 1;
while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;

// 32kHz timer period
NRF_RTC0->PRESCALER = 0;

// 30.5ms us compare value, generates EVENTS_COMPARE[0]
NRF_RTC0->CC[0] = 1000;

// Enable EVENTS_COMPARE[0] generation
NRF_RTC0->EVTENSET = RTC_EVTENSET_COMPARE0_Enabled << RTC_EVTENSET_COMPARE0_Pos;
// Enable IRQ on EVENTS_COMPARE[0]
NRF_RTC0->INTENSET = RTC_INTENSET_COMPARE0_Enabled << RTC_INTENSET_COMPARE0_Pos;

// Enable RTC IRQ and start the RTC
NVIC_EnableIRQ(RTC0_IRQn);
NRF_RTC0->TASKS_START = 1;

// Configure GPIO pin as output with standard drive strength.
NRF_GPIO->PIN_CNF[PIN_LED1] = (GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos) |
(GPIO_PIN_CNF_DRIVE_S0S1 << GPIO_PIN_CNF_DRIVE_Pos) |
(GPIO_PIN_CNF_INPUT_Connect << GPIO_PIN_CNF_INPUT_Pos) |
(GPIO_PIN_CNF_PULL_Disabled << GPIO_PIN_CNF_PULL_Pos) |
(GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos);

while (1)
{
// __WFE();
if(bLED1Set){
NRF_GPIO->OUTCLR = (1UL << PIN_LED1);
bLED1Set = false;
}else{
NRF_GPIO->OUTSET = (1UL << PIN_LED1);
bLED1Set = true;
}

}
}

// This IRQ handler will trigger every 30.5 ms
void RTC0_IRQHandler(void)
{
volatile uint32_t dummy;
if (NRF_RTC0->EVENTS_COMPARE[0] == 1)
{
NRF_RTC0->EVENTS_COMPARE[0] = 0;

// Increment compare value with 30.5 ms from current time.
NRF_RTC0->CC[0] = NRF_RTC0->COUNTER + 1000;

// Read back event register so ensure we have cleared it before exiting IRQ handler.
dummy = NRF_RTC0->EVENTS_COMPARE[0];
dummy;
}
}

[ovrebekk]

Hi Abir

If you don't use a SoftDevice I don't know why this code would cause a crash. 

Can you let me know what kind of hardware you are testing on?

Is it a standard DK, or some other kind of board?

If you can upload the entire project that would be great, then I can easily test it here. It should be enough to drag drop a file into your reply if you want to attach files. 

Best regards
Torbjørn

[hmolesworth]

Try this and also init the i/o pin before enabling the timer:

/ This IRQ handler will trigger every 30.5 ms
void RTC0_IRQHandler(void)
{
  if (NRF_RTC0->EVENTS_COMPARE[0] == 1)
  {
    NRF_RTC0->EVENTS_COMPARE[0] = 0;
    // COUNTER and COMPARE[n] registers are all 24-bit. It seems an intermediate sampled
    // value must be used as pRTC->CC[IDX_SYS_TICK] += N; does not work for some reason,
    // maybe requires so many cycles to read back and CountValue must be synchronous (unchanging)
    //  - COUNTER register read takes a fixed 5 x PCLK16M clock cycles
    volatile uint32_t CountValue = NRF_RTC0->COUNTER;
    // Increment compare value with 30.5 ms from current time.
    NRF_RTC0->CC[0] = CountValue + 1000;
    // Data Synchronization Barrier: completes when all explicit memory accesses before
    // last instruction completes to avoid spurious interrupt
    __DSB();
  }
}

[Abir Hossain]

The board is nrf52-DK, nrf52832, official board
basic-timer.zip

[Abir Hossain]

Thanks for the reply both ovrebekk and hmlesworth. I will try this changes too.
But I think it is more of a project setup issue.

I tried similar code on uVision and working fine. I am using Vscode and used an example Zphyre project as templete. So My guess is some components/config from Zphyre is conflicting with my attempt to make project baremetal. Thats why added the project here.

Thanks

[Abir Hossain]

Thanks for the reply both ovrebekk and hmlesworth. I will try this changes too.
But I think it is more of a project setup issue.

I tried similar code on uVision and working fine. I am using Vscode and used an example Zphyre project as templete. So My guess is some components/config from Zphyre is conflicting with my attempt to make project baremetal. Thats why added the project here.

Thanks