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Topic: Timer Interrupts on Due (Read 81 times) previous topic - next topic

MarkEMarkEMark

Hi all. I've implemented Sebastian Vik & cmaglie's timer code. I've got it working as is, with the LED. And I also tried a Serial.println and that works fine too.

However after transplanting the code to something more meaty (RGB Pixel light string) - the TC3_Handler only executes once.

The LEDs driver is using the hardware SPI channel - could it be anything to do with that? To rule out a clash of interrupts with the LED driver, I tried TC4/5 then TC0, but I still only get the first frame.

Any ideas? I'll post a video of the lights, if I get it working. (The code works otherwise - if I base the timer on time, it works fine)

I'll post the code, but you'd need the lights to see it:

https://github.com/MarkEMarkEMark/WS2801MEO

(note the previous version of the code works without the timer)

gst0098

Hi to all, I'm new to the arduino environment, I own an arduino due, I made some experiments with interrupts, apparently I cannot get the frequency higher than 250kHz, is this a known limit of the hardware ? I'm missing something, I read the datasheet and it states that TC_CMR_TCCLKS_TIMER_CLOCK1 is 84MHz / 2 = 41MHz so I was hoping that setting appropriately RA and RC (in my case 20 and 41 respectively) I would be able to acquire timer interrupts at 1MHz frequency.

Where am I wrong ?

Thanks in advance,
Giuseppe

gst0098

I answer myself, I was wrong, with correct values the timer interrupt can be triggered at 1MHz.
The problem was that the analogWrite is too slow to go to that frequency, so I digged into the arduino/sam7core sources and found how to use the SAM library directly, the code (much fast) that I wrote is:

// This function to configure a Timer was given some replies above, I changed only the used CLOCK.
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_CLOCK1);
  uint32_t rc = VARIANT_MCK/2/frequency; //2 because we selected TIMER_CLOCK1 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);
}

volatile boolean l;

void TC3_Handler()
{
  TC_GetStatus(TC1, 0);
  dacc_write_conversion_data(DAC0, (l = !l)*4095);
}

void setup() {
  Serial.begin(115200);
  pinMode(DAC0, OUTPUT);
  analogWriteResolution(12); 
  pmc_enable_periph_clk(DACC_INTERFACE_ID);
  dacc_reset(DACC_INTERFACE);
  dacc_set_transfer_mode(DACC_INTERFACE, 0);
  dacc_set_power_save(DACC_INTERFACE, 0, 0);
  dacc_set_timing(DACC_INTERFACE, 0x0, 1, 0x0);

  dacc_set_analog_control(DACC_INTERFACE, DACC_ACR_IBCTLCH0(0x02) |
                   DACC_ACR_IBCTLCH1(0x02) |
                   DACC_ACR_IBCTLDACCORE(0x01));
  dacc_disable_trigger(DACC_INTERFACE);
  dacc_set_channel_selection(DACC_INTERFACE, 0);
  dacc_enable_channel(DACC_INTERFACE, 0);

  // Start timer. Parameters are:

  // TC1 : timer counter. Can be TC0, TC1 or TC2
  // 0   : channel. Can be 0, 1 or 2
  // TC3_IRQn: irq number. See table.
  // 40  : frequency (in Hz)
  // The interrupt service routine is TC3_Handler. See table.

  startTimer(TC1, 0, TC3_IRQn, 1000000);
}


Thanks to all,
Giuseppe Stanghellini

DuaneB

what does this compile to ?

Code: [Select]
dacc_write_conversion_data(DAC0, (l = !l)*4095);

why not l = ~l;

with l initialised to 4095 -it should be a lot faster.

Duane B

rcarduino.blogspot.com

gst0098


what does this compile to ?

Code: [Select]
dacc_write_conversion_data(DAC0, (l = !l)*4095);

why not l = ~l;

with l initialised to 4095 -it should be a lot faster.

Duane B

rcarduino.blogspot.com


Good point! Nevertheless the code was timing correctly at 1MHz. Checked with a picoscope,

Giuseppe

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