Tone.cpp

/*
  Copyright (c) 2015 Arduino LLC.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "Tone.h"
#include "variant.h"

#define WAIT_TC16_REGS_SYNC(x) while(x->COUNT16.STATUS.bit.SYNCBUSY);

uint32_t toneMaxFrequency = F_CPU / 2;
uint32_t lastOutputPin = 0xFFFFFFFF;

volatile uint32_t *portToggleRegister;
volatile uint32_t *portClearRegister;
volatile uint32_t portBitMask;
volatile int64_t toggleCount;
volatile bool toneIsActive = false;

#define TONE_TC         TC5
#define TONE_TC_IRQn    TC5_IRQn
#define TONE_TC_TOP     0xFFFF
#define TONE_TC_CHANNEL 0
void TC5_Handler (void) __attribute__ ((weak, alias("Tone_Handler")));

static inline void resetTC (Tc* TCx)
{
  // Disable TCx
  TCx->COUNT16.CTRLA.reg &= ~TC_CTRLA_ENABLE;
  WAIT_TC16_REGS_SYNC(TCx)

  // Reset TCx
  TCx->COUNT16.CTRLA.reg = TC_CTRLA_SWRST;
  WAIT_TC16_REGS_SYNC(TCx)
  while (TCx->COUNT16.CTRLA.bit.SWRST);
}

void toneAccurateClock (uint32_t accurateSystemCoreClockFrequency)
{
  toneMaxFrequency = accurateSystemCoreClockFrequency / 2;
}

void tone (uint32_t outputPin, uint32_t frequency, uint32_t duration)
{
  if (toneIsActive && (outputPin != lastOutputPin))
    noTone(lastOutputPin);

  //
  // Calculate best prescaler divider and comparator value for a 16 bit TC peripheral
  //

  uint32_t prescalerConfigBits;
  uint32_t ccValue;

  ccValue = toneMaxFrequency / frequency - 1;
  prescalerConfigBits = TC_CTRLA_PRESCALER_DIV1;

  if (ccValue > TONE_TC_TOP)
  {
    ccValue = toneMaxFrequency / frequency / 2 - 1;
    prescalerConfigBits = TC_CTRLA_PRESCALER_DIV2;

    if (ccValue > TONE_TC_TOP)
    {
      ccValue = toneMaxFrequency / frequency / 4 - 1;
      prescalerConfigBits = TC_CTRLA_PRESCALER_DIV4;

      if (ccValue > TONE_TC_TOP)
      {
        ccValue = toneMaxFrequency / frequency / 8 - 1;
        prescalerConfigBits = TC_CTRLA_PRESCALER_DIV8;

        if (ccValue > TONE_TC_TOP)
        {
          ccValue = toneMaxFrequency / frequency / 16 - 1;
          prescalerConfigBits = TC_CTRLA_PRESCALER_DIV16;

          if (ccValue > TONE_TC_TOP)
          {
            ccValue = toneMaxFrequency / frequency / 64 - 1;
            prescalerConfigBits = TC_CTRLA_PRESCALER_DIV64;

            if (ccValue > TONE_TC_TOP)
            {
              ccValue = toneMaxFrequency / frequency / 256 - 1;
              prescalerConfigBits = TC_CTRLA_PRESCALER_DIV256;

              if (ccValue > TONE_TC_TOP)
              {
                ccValue = toneMaxFrequency / frequency / 1024 - 1;
                prescalerConfigBits = TC_CTRLA_PRESCALER_DIV1024;
              }
            }
          }
        }
      }
    }
  }

  toggleCount = (duration > 0 ? frequency * duration * 2 / 1000UL : -1);

  // Enable GCLK for TC4 and TC5 (timer counter input clock)
  GCLK->CLKCTRL.reg = (uint16_t) (GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 | GCLK_CLKCTRL_ID(GCM_TC4_TC5));
  while (GCLK->STATUS.bit.SYNCBUSY);

  resetTC(TONE_TC);

  // Set Timer counter Mode to 16 bits
  TONE_TC->COUNT16.CTRLA.reg |= TC_CTRLA_MODE_COUNT16;

  // Set TONE_TC mode as match frequency
  TONE_TC->COUNT16.CTRLA.reg |= TC_CTRLA_WAVEGEN_MFRQ;

  TONE_TC->COUNT16.CTRLA.reg |= prescalerConfigBits;

  TONE_TC->COUNT16.CC[TONE_TC_CHANNEL].reg = (uint16_t) ccValue;
  WAIT_TC16_REGS_SYNC(TONE_TC)

  // Configure interrupt request
  NVIC_DisableIRQ(TONE_TC_IRQn);
  NVIC_ClearPendingIRQ(TONE_TC_IRQn);
  NVIC_SetPriority(TONE_TC_IRQn, 0);
  NVIC_EnableIRQ(TONE_TC_IRQn);

  portToggleRegister = &(PORT->Group[g_APinDescription[outputPin].ulPort].OUTTGL.reg);
  portClearRegister = &(PORT->Group[g_APinDescription[outputPin].ulPort].OUTCLR.reg);
  portBitMask = (1ul << g_APinDescription[outputPin].ulPin);

  // Enable the TONE_TC interrupt request
  TONE_TC->COUNT16.INTENSET.bit.MC0 = 1;

  lastOutputPin = outputPin;
  digitalWrite(outputPin, LOW);
  pinMode(outputPin, OUTPUT);
  toneIsActive = true;

  // Enable TONE_TC
  TONE_TC->COUNT16.CTRLA.reg |= TC_CTRLA_ENABLE;
  WAIT_TC16_REGS_SYNC(TONE_TC)
}

void noTone (uint32_t outputPin)
{
  resetTC(TONE_TC);
  digitalWrite(outputPin, LOW);
  toneIsActive = false;
}

#ifdef __cplusplus
extern "C" {
#endif

void Tone_Handler (void)
{
  if (toggleCount != 0)
  {
    // Toggle the ouput pin
    *portToggleRegister = portBitMask;

    if (toggleCount > 0)
      --toggleCount;

    // Clear the interrupt
    TONE_TC->COUNT16.INTFLAG.bit.MC0 = 1;
  }
  else
  {
    resetTC(TONE_TC);
    *portClearRegister = portBitMask;
    toneIsActive = false;
  }
}

#ifdef __cplusplus
}
#endif