Porting a Library

Troubleshooting
1

I’m trying to port the toneAC library so i can drive a piezo utilizing differential drive. I’ve started by replacing the _BV macro and adding application.h but don’t know how to continue. I haven’t found too many resources on how to do this so I would appreciate some help. It’s a short library so i’ll post what i have here. On the other hand, if you know of a better way to use differential drive with a piezo (or resources on how to port a library), please let me know. Thanks for any help you may be able to provide!

.h

// PURPOSE:
// Replacement to the standard tone library with the advantage of nearly twice
// the volume, higher frequencies (even if running at a lower clock speed),
// much higher quality (no clicking), nearly 2k smaller compiled code and less
// stress on the speaker. Disadvantages are that it must use certain pins and
// it uses two pins instead of one. But, if you're flexible with your pin
// choices, this is a great upgrade. It also uses timer 1 instead of timer 2,
// which may free up a conflict you have with the tone library. It exclusively
// uses port registers for the fastest and smallest code possible.
//
// USAGE:
// Should work with most Arduino and compatible systems including Teensy 2.0.
// Designed with Arduino 1.02. You must use the two PWM pins for timer 1 on
// your Arduino (see CONNECTION below). Connect your piezo or speaker up the
// listed pins and use the toneAC() command instad of tone() for the benefits
// mentioned above.
//
// CONNECTION:
//   ATmega328, ATmega128, Uno, etc. - pins  9 & 10
//   ATmega2560, ATmega1280, Mega    - pins 11 & 12
//   Teensy 2.0 (maybe Leonardo?)    - pins 14 & 15
//
// SYNTAX:
//   toneAC(frequency)                 - Play the specified frequency indefinitely.
//   toneAC(frequency, volume)         - You can optionally select a certain volume level (0 - 100).
//   toneAC(frequency, volume, length) - Also optionally set the length to play in milliseconds.
//   toneAC()                          - Stop output.
//   noToneAC()                        - Same as toneAC().
//
// HISTORY:
// 01/11/2013 v1.0 - First release.
//
// ---------------------------------------------------------------------------

#ifndef toneAC_h
  #define toneAC_h

  #if defined (SPARK)
    #include "application.h"
  #else
    #if defined(ARDUINO) && ARDUINO >= 100
      #include "Arduino.h"
    #else
      #include "WProgram.h"
    #endif
  #endif

  #if defined (__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__) || defined(__AVR_ATmega1284P__)
    #define PWMT1AMASK DDB5
    #define PWMT1BMASK DDB6
  #else
    #define PWMT1AMASK DDB1
    #define PWMT1BMASK DDB2
  #endif

  void toneAC(unsigned long frequency = 0, uint8_t volume = 100, unsigned long length = 0);
  void noToneAC();

#endif

.cpp

#include "toneAC.h"

void toneAC(unsigned long frequency, uint8_t volume, unsigned long length) {
  if (frequency == 0 || volume == 0) { noToneAC(); return; } // If frequency or volume is 0, turn off sound and return.
  if (volume > 199) volume = 199;                            // Make sure volume is in range (100 is full volume, 50% duty).

  DDRB |= (1 << (PWMT1AMASK)) | (1 << (PWMT1BMASK)); // Set timer 1 PWM pins to OUTPUT (because analogWrite does it too).

  uint8_t prescaler = (1 << (CS10));                   // Try using prescaler 1 first.
  unsigned long limit = F_CPU / frequency / 2 - 1; // Calculate the upper limit.
  if (limit > 65535) {                      // If not in the range for prescaler 1, use prescaler 64 (below 123 Hz @ 16 MHz).
    limit = F_CPU / frequency / 2 / 64 - 1; // Calculate the upper limit using prescaler 64.
    prescaler |= (1 << (CS11));                 // Add the prescaler bit.
  }
  unsigned int duty = max(limit * (unsigned long) volume / 200, 1); // Calculate the duty cycle (volume).

  ICR1   = limit;                       // Upper limit.
  TCCR1B = (1 << (WGM13))  | prescaler;     // PWM, Phase and Frequency Corrected (ICR1) and prescaler.
  OCR1A  = OCR1B = duty;                // Set the duty cycle (volume).
  TCCR1A = (1 << (COM1A1)) | (1 << (COM1B1)) | (1 << (COM1B0)); // Inverted / none-inverted mode (AC).

  if (length) { delay(length); noToneAC(); } // Just a simple delay, doesn't return control till finished.
}

void noToneAC() {
  TCCR1B = (1 << (CS11));        // Default clock prescaler of 8.
  TCCR1A = (1 << (WGM10));       // Set to defaults so PWM can work like normal (PWM, phase corrected, 8bit).
  PORTB &= ~(1 << (PWMT1AMASK)); // Set timer 1 PWM pins to LOW.
  PORTB &= ~(1 << (PWMT1BMASK));
}