Lpc2000

Hi Leon -
I don't step deep into it but as you using variables greater 8 bits what's
about little-endian/big-endian confusion, maybe?
Regards -
Henry

-----Urspr\ufffdngliche Nachricht-----
Von: Leon Heller <leon_heller@...>
An: lpc2100@yahoogroups.com <lpc2100@yahoogroups.com>
Datum: Mittwoch, 3. Dezember 2003 11:46
Betreff: [lpc2100] Problem with DDS


>I'm using the following code for software direct digital waveform
synthesis:
>
>int main(void)
>{
>  unsigned int i;
>  unsigned long int acc, adder;
>  unsigned int ptr, temp;
>
>  initPLL();
>  MAMCR = 0;
>  MAMTIM = 5;
>  MAMCR = 2;
>  VPBDIV = 0x01;
>  portInit();
>  //main loop
>  //add value to accumulator
>  //load byte from current table
>  //output byte to port
>  //repeat
>
>  adder = 2000;               //set up adder
>  acc = 0;                    //clear accumulator
>  while (1)
>  {
>    acc = acc + adder;      //update phase accumulator
>    ptr = (acc &= 0xFF);    //pointer into table
>    IOSET = square[ptr] << 8;//output byte to port
>    IOCLR = ~(square[ptr] << 8);
>  }
>  return 0;
>}
>
>but I can't get an equal mark-space ratio out of it for a square wave, and
>sine waves are completely screwed up.
>
>The following code for an AVR works very well:
>
>; main loop
>;
>; r28,r29,r30 is the phase accumulator
>;   r24,r25,r26 is the adder value determining frequency
>;
>;  add value to accumulator
>; load byte from current table in ROM
>; output byte to port
>; repeat
>;
>LOOP1:
>  add  r28,r24   ; 1
>  adc  r29,r25   ; 1
>  adc  r30,r26   ; 1
>  lpm      ; 3
>  out  PORTB,r0  ; 1
>  rjmp LOOP1   ; 2 => 9 cycles
>
>I'm using the same AD557 8-bit DAC and the same look-up tables. I'm
>obviously doing something silly, but I can't see what it is. Can anyone
>help?
>
>Leon
>--
>Leon Heller, G1HSM
>Email: aqzf13@...
>http://www.geocities.com/leon_heller
>
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