Nano IOT Timer Interrupt

Projects Programming
1

Managed to get a timer-ISR running using timer TC3. The ISR fires at the expected rate.
But if the interrupt is enabled, and I want to upload changed code, it does not work. I have to go via the Bootloader, so I suspect that there are resource conflicts: maybe TC3 or the changed GCLK is also used by hidden parts of the arduino base-sw-packet.

Here the init-funct that configures the timer:

void TIM_TimerInit(void) 
{
  // Set GCLK0 (48MHz) as clock source for timer TC3
  GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 | GCLK_CLKCTRL_ID_TCC2_TC3;    
  // Put the timer TC3 into match frequency (MFRQ) mode, divide clock by 1024, reset timer on the next prescaler pulse (not GCLK)
  TC3->COUNT16.CTRLA.reg = TC_CTRLA_WAVEGEN_MFRQ | TC_CTRLA_PRESCALER_DIV1024 | TC_CTRLA_PRESCSYNC_PRESC;      

  // Set TC3 period to 1Hz: 48MHz / (1024 * 3Hz) - 1 = 15624, wait for sync
  TC3->COUNT16.CC[0].reg = 15624;
  while (TC3->COUNT16.STATUS.bit.SYNCBUSY);               

  // Enable TC3 overflow interrupts
  TC3->COUNT16.INTENSET.reg = TC_INTENSET_OVF;
  // Enable TC3, wait for sync
  TC3->COUNT16.CTRLA.bit.ENABLE = 1;
  while (TC3->COUNT16.STATUS.bit.SYNCBUSY);

  // set NVIC priority for TC3 to 0 (highest), connect TC3 to NVIC
  NVIC_SetPriority(TC3_IRQn, 0);
  NVIC_EnableIRQ(TC3_IRQn);         
}

Does anybody know how to find out which on-chip resources can be used without messing up something else?

2

What happends when you use timer 4?

// Example: Switch to TC4
void TIM_TimerInit(void) {
 
  // Set GCLK0 for TC4
  GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 | GCLK_CLKCTRL_ID_TC4_TC5;
  
  // Configure TC4
  TC4->COUNT16.CTRLA.reg = TC_CTRLA_WAVEGEN_MFRQ | TC_CTRLA_PRESCALER_DIV1024 | TC_CTRLA_PRESCSYNC_PRESC;

																		   
  TC4->COUNT16.CC[0].reg = 15624; // Adjust for desired frequency
  while (TC4->COUNT16.STATUS.bit.SYNCBUSY);
  
  // Enable interrupts
  TC4->COUNT16.INTENSET.reg = TC_INTENSET_OVF;
							  
  TC4->COUNT16.CTRLA.bit.ENABLE = 1;
  while (TC4->COUNT16.STATUS.bit.SYNCBUSY);
  
																  
  NVIC_SetPriority(TC4_IRQn, 0);
  NVIC_EnableIRQ(TC4_IRQn);
}

// ISR for TC4
void TC4_Handler() {
  // Your ISR code
  TC4->COUNT16.INTFLAG.reg = TC_INTFLAG_OVF; // Clear interrupt
}
3

Hi StefanL38,

thanks for your proposal. I think I found the root cause - although I do not understand it completely:

Timer 3 is still in use.
I gave a different name to my ISR (to stick to my personal naming conventions :-): Its name was ISR_TIM_TC3.

At the top of the file I added:
#define TC3_Handler ISR_TIM_TC3

After using the original name, and removing the #define, everything works as expected.

Nevertheless thanks a lot for your support !

... and just a minute ago I found that the renaming itself is not the problem, but the #define was the wrong way around. It should be: #define ISR_TIM_TC3 TC3_Handler

4

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