External clock input on timer0

youthreewire · June 21, 2015, 1:55am

Hello,

I want to set up the timer interrupt 1 for external clock input on the Due.How do I do it? I have some code for the timer but it is set to internal clock4. I need to give it an external 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_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);
}

I need the Due code to do the following in the atmega328 code below.

// setup timer1 for codec clock division
  TCCR1A = 0x00; // set to CTC mode
  TCCR1B = 0x0f; // set to CTC mode, external clock
  TCCR1C = 0x00; // not used
  TCNT1H = 0x00; // clear the counter
  TCNT1H = 0x00;
  #if SAMPLE_RATE == 88
    OCR1AH = 0x00; // set the counter top
    OCR1AL = 0x3f;
  #elif (SAMPLE_RATE == 44) || (SAMPLE_RATE == 22)
    OCR1AH = 0x00; // set the counter top
    OCR1AL = 0x7f;
  #elif SAMPLE_RATE == 8
    OCR1AH = 0x02; // set the counter top
    OCR1AL = 0xbf;
  #elif SAMPLE_RATE == 2
    OCR1AH = 0x04; // set the counter top
    OCR1AL = 0x7f;
  #endif
  TIMSK1 = 0x02; // turn on compare match interrupt
  
  // turn off all enabled interrupts (delay and wire)
  TIMSK0 = 0x00;
  TWCR = 0x00;

  sei(); // turn on interrupts

youthreewire · June 21, 2015, 10:05am

I found some information about the Due timers here:

Here they mention about connecting an external clock but TCLK0 but also mentioned about I/O Lines TIOA0 ,TIOB0. i am confused here.

github.com

ivanseidel/DueTimer/blob/master/TimerCounter.md

# The Timer Counter blocks of Arduino Due's AT91SAM3X8E

The AT91SAM3X8E embedds nine general-purpose 32-bit timers/counters. They are organized in three blocks (`TC0`, `TC1`, `TC2`) each containing three channels (`0`, `1`, `2`).
Each block and channel has input lines for their clock and input/output lines which can be used in different ways, such as PWM pins etc.


### Resources

Information on the Timer Counter and its I/O signals pins can be found here:

* Section **37 Timer Counter (TC)** in the [Atmel SAM3X Datasheet][]  
  You find this chapter on the pages 869 through 920. It explains in detail how to operate the counter in different modes and has nice diagrams that show you how the clock input works and how to set up interrupts based on counter values etc.
* [Arduino Due's SAM3X Pin Mapping][] and the 
* [Arduino Due pinout diagram][].

### The Timer Counter Signals / Pins

Many of the I/O lines of the Timer Counter are directly accessible on pin headers of the Arduino Due board. This section helps you to find out which of them are and which are not.

In order to actually connect those signals (`TCLKx`, `TIOAx` and `TIOBx`) to the pins on the Arduino Due, you must tell the Parallel I/O Controllers (`PIOA`, `PIOB`, `PIOC` or `PIOD`) to set up their mux (multiplexer) accordingly.<br />

This file has been truncated. show original

youthreewire · June 21, 2015, 11:01am

I found this in the data sheet
"Block Mode Register (TC_BMR)—defines the external clock inputs for each channel, allowing them to be
chained"

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External clock input on timer0

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