Maple Frequency Measurement Example

/*
* This paste provided by Chris Troutner from http://thesolarpowerexpert.com
*
* This code is based on publicly available code available at the following sources:
* http://pastebin.com/NQtbVCFh
* http://forums.leaflabs.com/topic.php?id=1038
*
* It's inteded for a Maple Rev 5 from leaflabs.com
*/

#include <timer.h>



int value = 0;
int count = 0;

int overflow_flag = 0;

HardwareTimer timer4 = HardwareTimer(4);

//quick method to return if there's anyone on the other end of the serialusb link yet.
boolean isConnected(){
  return (SerialUSB.isConnected() && (SerialUSB.getDTR() || SerialUSB.getRTS()));
}

void setup()
{

  SerialUSB.begin();
  while(!isConnected()); //wait till console attaches.
  SerialUSB.println("Hello!");

  //Setup Timer4 Channel 1 (pin 5) as an input
  pinMode(5, INPUT);

  //Configure pin 7 as an output
  pinMode(7, OUTPUT);

  setup_timer();

}

void __measurePulse_irq()
{

  //For some reason, the interrupt is triggred as soon as
  //the device is turned on. This gets around that bug.
  if( count == 0 )
    return;
  else {

    if(~overflow_flag)
      value = TIMER4_BASE->CCR1;        //read the captured value
    else {
      value = 0;
      overflow_flag = 0;
    }


    timer4.setCount(0);  //Zero timer
  }
}

void handle_overflow() {

  overflow_flag = 1;
}

void loop() {

  //Display the value very 500 mS
  if( count == 100 ) {
    //delay(500);
    SerialUSB.println(value);
    //value = 0;
    count = 0;
  }


  //Pulse pin 7 at a rate of 100 Hz @ 50% DC
  digitalWrite(7, HIGH);
  delay(5);
  digitalWrite(7, LOW);
  delay(5);

  count++;

}


//Halt processor and flash LED - used for debugging
void HaltAll(void) {

  //Timer4.pause();
  timer4.pause();
  pinMode(BOARD_LED_PIN, OUTPUT);

  while(1) {

     toggleLED();
     delay(1000);

  }

}

/*
This is a mis-mash of code from these two sources:
http://pastebin.com/NQtbVCFh
http://forums.leaflabs.com/topic.php?id=1038
*/
void setup_timer(void) {

  //Create a pointer to the timer (why?)
  timer_dev *t = TIMER4;

  //Initialize timer
  timer4.pause();

  /*
  A prescaler of 288 means that at 72MHz, I get the following:
  100 Hz = 2510
  10 Hz = 25084
  */
  timer4.setPrescaleFactor(288);

  timer4.setOverflow(65535);
  timer4.setCount(0);

  //New code to set overflow timer
  timer4.setMode(2, TIMER_OUTPUT_COMPARE); //Set this channel to compare
  timer4.setCompare(2, 65534); //Set the compare for the channel to the overflow vale
  timer4.attachInterrupt(2, handle_overflow); //Assign the interrupt handler

  timer4.refresh();

  //Create a pointer to the timer registers (why?)
  timer_reg_map r = t->regs;


  //capture compare regs TIMx_CCRx used to hold val after a transition on corresponding ICx

  //when cap occurs, flag CCXIF (TIMx_SR register) is set,
  //and interrupt, or dma req can be sent if they are enabled.

  //if cap occurs while flag is already high CCxOF (overcapture) flag is set..

  //CCIX can be cleared by writing 0, or by reading the capped data from TIMx_CCRx
  //CCxOF is cleared by writing 0 to it.

  //Capture/Compare 1 Selection
  //  set CC1S bits to 01 in the capture compare mode register.
  //  01 selects TI1 as the input to use. (page 336 stm32 reference)
  //  (assuming here that TI1 is D6, according to maple master pin map)
  //CC1S bits are bits 0,1
  bitSet(r.adv->CCMR1, 0);
  bitClear(r.adv->CCMR1, 1);


  //Input Capture 1 Filter.
  //  need to set IC1F bits according to a table saying how long
  //  we should wait for a signal to be 'stable' to validate a transition
  //  on the input.
  //  (page 336 stm32 reference)
  //IC1F bits are bits 7,6,5,4
  bitClear(r.adv->CCMR1, 7);
  bitClear(r.adv->CCMR1, 6);
  bitSet(r.adv->CCMR1, 5);
  bitSet(r.adv->CCMR1, 4);

  //sort out the input capture prescaler..
  //00 no prescaler.. capture is done as soon as edge is detected
  bitClear(r.adv->CCMR1, 3);
  bitClear(r.adv->CCMR1, 2);

  //This command does everything above to the CCMR1 register.
  //TIMER4_BASE->CCMR1 = 0x00F1;        //channel 1 configure as input, IC1 mapped on TI1

  //select the edge for the transition on TI1 channel using CC1P in CCER
  //CC1P is bit 1 of CCER (page 339)
  // 0 = rising
  // 1 = falling
  bitClear(r.adv->CCER,1);

  //set the CC1E bit to enable capture from the counter.
  //CCE1 is bit 0 of CCER (page 339)
  //Enable capture
  bitSet(r.adv->CCER,0);


  //TIMER4_BASE->CCMR2 = 0x0000;        //channels 3&4 disabled
  //TIMER4_BASE->CCER = 0x0001;     //configure channel 1 as an input
  //TIMER4_BASE->SMCR = 0x0000;     //all slave modes disabled, CC transitions on clock
 //TIMER4_BASE->CR1 = 0x0001;       //enable the counter
  //TIMER4_BASE->CR2 = 0x0000;      //connect TIM4_CH1 pin to TI1 input
  //TIMER4_BASE->PSC = 0x00FF;      //set a random large prescalar just for testing

  //timer_attach_interrupt(TIMER4, TIMER_CC1_INTERRUPT, __measurePulse_irq);
  timer4.attachInterrupt(1, __measurePulse_irq);

  //timer_resume(TIMER4);
  timer4.resume();

  /*value = TIMER4_BASE->CCMR2;
  SerialUSB.println("Value is: ");
  SerialUSB.println(value);
  HaltAll();
  */
}