Arduino Mega 2560 compatability?

Hey guys, I just threw some old code from a project I started on a duemilanove. The code worked absolutely fine on it, but on the mega 2560 it doesn't work at all. Had the same hardware plugged into the same pins, switched the com channels when switching boards, switched the board type under tools. Does the mega have different syntax or is mine just busted? I ordered this and a few more parts from a website called liquidware. Are my problems caused by my search for the lowest price, and subsequently lower quality?

Here's the code:

#include "avr/pgmspace.h"

// table of 256 sine values / one sine period / stored in flash memory
PROGMEM  prog_uchar sine256[]  = {

#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))

int ledPin = 13;                 // LED pin 7
int testPin = 7;
int t2Pin = 6;
byte bb;

double dfreq;
// const double refclk=31372.549;  // =16MHz / 510
const double refclk=31376.6;      // measured

// variables used inside interrupt service declared as voilatile
volatile byte icnt;              // var inside interrupt
volatile byte icnt1;             // var inside interrupt
volatile byte c4ms;              // counter incremented all 4ms
volatile unsigned long phaccu;   // pahse accumulator
volatile unsigned long tword_m;  // dds tuning word m

void setup()
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
  Serial.begin(115200);        // connect to the serial port
  Serial.println("DDS Test");

  pinMode(6, OUTPUT);      // sets the digital pin as output
  pinMode(7, OUTPUT);      // sets the digital pin as output
  pinMode(11, OUTPUT);     // pin11= PWM  output / frequency output


  // disable interrupts to avoid timing distortion
  cbi (TIMSK0,TOIE0);              // disable Timer0 !!! delay() is now not available
  sbi (TIMSK2,TOIE2);              // enable Timer2 Interrupt

  dfreq=1000.0;                    // initial output frequency = 1000.o Hz
  tword_m=pow(2,32)*dfreq/refclk;  // calulate DDS new tuning word 

void loop()
  while(1) {
     if (c4ms > 250) {                 // timer / wait fou a full second
      dfreq=500;             // adjust output frequency to 500 Hz

      cbi (TIMSK2,TOIE2);              // disble Timer2 Interrupt
      tword_m=pow(2,32)*dfreq/refclk;  // calulate DDS new tuning word
      sbi (TIMSK2,TOIE2);              // enable Timer2 Interrupt 

      Serial.print("  ");

   sbi(PORTD,6); // Test / set PORTD,7 high to observe timing with a scope
   cbi(PORTD,6); // Test /reset PORTD,7 high to observe timing with a scope
// timer2 setup
// set prscaler to 1, PWM mode to phase correct PWM,  16000000/510 = 31372.55 Hz clock
void Setup_timer2() {

// Timer2 Clock Prescaler to : 1
  sbi (TCCR2B, CS20);
  cbi (TCCR2B, CS21);
  cbi (TCCR2B, CS22);

  // Timer2 PWM Mode set to Phase Correct PWM
  cbi (TCCR2A, COM2A0);  // clear Compare Match
  sbi (TCCR2A, COM2A1);

  sbi (TCCR2A, WGM20);  // Mode 1  / Phase Correct PWM
  cbi (TCCR2A, WGM21);
  cbi (TCCR2B, WGM22);

// Timer2 Interrupt Service at 31372,550 KHz = 32uSec
// this is the timebase REFCLOCK for the DDS generator
// FOUT = (M (REFCLK)) / (2 exp 32)
// runtime : 8 microseconds ( inclusive push and pop)
ISR(TIMER2_OVF_vect) {

  sbi(PORTD,7);          // Test / set PORTD,7 high to observe timing with a oscope

  phaccu=phaccu+tword_m; // soft DDS, phase accu with 32 bits
  icnt=phaccu >> 24;     // use upper 8 bits for phase accu as frequency information
                         // read value fron ROM sine table and send to PWM DAC
  OCR2A=pgm_read_byte_near(sine256 + icnt);    

  if(icnt1++ == 125) {  // increment variable c4ms all 4 milliseconds

 cbi(PORTD,7);            // reset PORTD,7

Which, when pin 11 and ground are connected to a 1/4" mono jack, will play a repeating note. Again, this works on the duemilanove, but not the mega 2560. Thanks.

Take another look at your program.

My 2560 won't run it either.

There are some obvious pin number errors I think.

Some comments on what each (substantive) line does might be worth while.

there's a few extra pins in there that are to be used for oscilloscope monitoring of the sine wave. i don't use those. i also didnt create this code, i've only ever slightly altered it. i really dont know much about how it works, i only abuse it. all i know is that the same exact code works on the duemilanove.

i cut out a good few lines of code that weren’t necessary. that new version of the code still works just fine on the duemilanove, but still nothing on the mega 2560. could someone please check to see if this works on the old mega’s? if it does i’m just going to go that route instead.

all you need for wiring is digital pin 11 out to the hot prong on a 1/4" jack and a ground to the jacks ground. plug in a pair of headphones and you’ll hear a continuous beep.

The code looks like it was designed specifically for the Atmega328. Most of that code is using direct C code and not Arduino functions. You will probably have to change the timers or ports that are used to make it work on the Atmega2560. Normally this is done in the background via the Arduiono IDE but in this case the code bypasses these functions, probably because it is very dependent on timing to do what it needs to do. This is most likely not a hardware problem but a lower level programming issue. Unfortunately I haven't worked with this type of code enough to help you fix it, but that should point you in the right direction.

The Arduino Cookbook chapter 18 has a few sketches which show how to control the registers and explain some of the board differences.

The Mega2560 has significantly more ports, Serial ports, timers and other goodies. I regularly get caught having to modify sketches.

I could type in some of the example sketches in the Cookbook -- but you can do that just as easily as me.

Ah, thank you gents. I did read a few things about different timers being involved with the mega. And I'll be checking that book out today! Thanks for the suggestions.

I think on the Mega 2560 you need to use pin 10 for timer2 instead of pin 11.