Timer Interrupts on Due

system · April 20, 2013, 8:29pm

Using this code, you can set a timer for any of the ISRs TC0_Handler through TC8_Handler, see table of parameters below. It is possible to use the timers without a physically mapped pin, such as TC1 channel 0 (TC3_Handler) shown here:
volatile boolean l;

//TC1 ch 0
void TC3_Handler()
{
        TC_GetStatus(TC1, 0);
        digitalWrite(13, l = !l);
}

void startTimer(Tc *tc, uint32_t channel, IRQn_Type irq, uint32_t frequency) {
        pmc_set_writeprotect(false);
        pmc_enable_periph_clk((uint32_t)irq);
        TC_Configure(tc, channel, TC_CMR_WAVE | TC_CMR_WAVSEL_UP_RC | TC_CMR_TCCLKS_TIMER_CLOCK4);
        uint32_t rc = VARIANT_MCK/128/frequency; //128 because we selected TIMER_CLOCK4 above
        TC_SetRA(tc, channel, rc/2); //50% high, 50% low
        TC_SetRC(tc, channel, rc);
        TC_Start(tc, channel);
        tc->TC_CHANNEL[channel].TC_IER=TC_IER_CPCS;
        tc->TC_CHANNEL[channel].TC_IDR=~TC_IER_CPCS;
        NVIC_EnableIRQ(irq);
}

void setup(){
        pinMode(13,OUTPUT);
        startTimer(TC1, 0, TC3_IRQn, 4); //TC1 channel 0, the IRQ for that channel and the desired frequency
}

void loop(){
}
Here is the table of parameters:

ISR/IRQ TC Channel Due pins

TC0 TC0 0 2, 13

TC1 TC0 1 60, 61

TC2 TC0 2 58

TC3 TC1 0 none <- this line in the example above

TC4 TC1 1 none

TC5 TC1 2 none

TC6 TC2 0 4, 5

TC7 TC2 1 3, 10

TC8 TC2 2 11, 12

I'm a bit confused about the code for the startTimer function.

-What is the purpose of TC3_Handler() and how does it interact with startTimer()?
-Once startTimer() is called, how do I stop the timer(how do I disable PWM)?
-There's a few lines that I don't understand in startTimer():

        TC_Configure(tc, channel, TC_CMR_WAVE | TC_CMR_WAVSEL_UP_RC | TC_CMR_TCCLKS_TIMER_CLOCK4); <--- How does TC_Configure() work? Where can I find reference about this?
        uint32_t rc = VARIANT_MCK/128/frequency; <---------- is VARIANT_MCK the frequency of arduino DUE(84MHz)? What does rc do?
        TC_SetRA(tc, channel, rc/2); //50% high, 50% low<----sets the duty cycle? 
        TC_SetRC(tc, channel, rc);<---------- what is this line for?
        TC_Start(tc, channel);<---------------enables PWM? How does it work?
        tc->TC_CHANNEL[channel].TC_IER=TC_IER_CPCS;<----------What does this line do?
        tc->TC_CHANNEL[channel].TC_IDR=~TC_IER_CPCS;<--------What does this line do?
        NVIC_EnableIRQ(irq); <-----enables interrupt?

Topic		Replies	Views
Hardware Timer Interrupts on the Due Arduino Due	3	1603	May 6, 2021
another timer question Arduino Due	2	1321	May 6, 2021
Due Interrupt code from Uno Arduino Due	3	1365	May 6, 2021
Could someone help me about this DUE Timer or Interrupt code? Arduino Due	5	3792	May 6, 2021
problem with Timer & Interrupt (Due) Arduino Due	3	944	May 6, 2021

ISR/IRQ	TC	Channel	Due pins
TC0	TC0	0	2, 13
TC1	TC0	1	60, 61
TC2	TC0	2	58
TC3	TC1	0	none <- this line in the example above
TC4	TC1	1	none
TC5	TC1	2	none
TC6	TC2	0	4, 5
TC7	TC2	1	3, 10
TC8	TC2	2	11, 12

Timer Interrupts on Due

Related Topics