Hi all. 
I have a question regarding PROGMEM which I am using to store sinewave arrays and notetable arrays.
Its for a synth project I am working on.
I wanted to try changing waveshapes so I added another wavetable in PROGMEM and changed the program accordingly but the program just acted the same. I started to wonder if the old wave was still in the PROGMEM memory so I deleted the array information leaving the PROGMEM arrays empty but when I re uploaded the code THE WAVES STILL PLAYED!!! 
How could this be happening?
How can I make sure that upon every upload, the arrays are reuploaded anew and its not just using the ones from before??
Does PROGMEM require special treatment?
Any help appreciated.
Steve.
Post your code. Perhaps you are not doing what you think you are doing.
I wanted to try changing waveshapes so I added another wavetable in PROGMEM and changed the program accordingly but the program just acted the same.
This will not normally happen. I have done the same thing myself and have not seen this effect.
New code will overwrite old code in Program memory but if the new code is shorter than the old code there will be bits of the old code left. Loading new code will not cause blanking out of areas of memory that are not used by the new code. This should not affect your program as you should not be able to reference it. However, a rouge or hardwired pointer could under some circumstances access the remnants of old code.
However, a rouge or hardwired pointer
"Rogue", not red
Hi Crossroads. OK. I' posting the entire program below.
You can see the PROGMEM arrays near the top & they are used in the synthesis engine near the bottom. In the wave update stage and in the interrupt. Oh, I have to say I'm using an XAduino board which uses an ATXMEGA128a3 and Arduino 1.0.1 which has been modified for the XMEGA.
I'vec missed out the MIDI part of the code to shorten the length so it fits. It doesn't have to do with PROGMEM calls anyway..
Hope someone can help.
//Modification of GordonJCP's FMTOY to work on XMEGA128a3.
// Uses on board DAC as opposed to PWM.
//Controlled by Bluetooth through Serial port 0 from an Android tablet.
//Thanks to Erik.T (AVR_Freaks) for the advice on using the DAC.
#include<avr/io.h>
#include<avr/interrupt.h>
#include <avr/pgmspace.h>
#include <stdint.h>
#include <avr/wdt.h>
//#define SERIAL
// table of 256 sine values / one sine period / stored in flash memory
PROGMEM byte sine256[] = {
127,130,133,136,139,143,146,149,152,155,158,161,164,167,170,173,176,178,181,184,187,190,192,195,198,200,203,205,208,210,212,215,217,219,221,223,225,227,229,231,233,234,236,238,239,240,
242,243,244,245,247,248,249,249,250,251,252,252,253,253,253,254,254,254,254,254,254,254,253,253,253,252,252,251,250,249,249,248,247,245,244,243,242,240,239,238,236,234,233,231,229,227,225,223,
221,219,217,215,212,210,208,205,203,200,198,195,192,190,187,184,181,178,176,173,170,167,164,161,158,155,152,149,146,143,139,136,133,130,127,124,121,118,115,111,108,105,102,99,96,93,90,87,84,81,78,
76,73,70,67,64,62,59,56,54,51,49,46,44,42,39,37,35,33,31,29,27,25,23,21,20,18,16,15,14,12,11,10,9,7,6,5,5,4,3,2,2,1,1,1,0,0,0,0,0,0,0,1,1,1,2,2,3,4,5,5,6,7,9,10,11,12,14,15,16,18,20,21,23,25,27,29,31,
33,35,37,39,42,44,46,49,51,54,56,59,62,64,67,70,73,76,78,81,84,87,90,93,96,99,102,105,108,111,115,118,121,124
};
PROGMEM byte sine256_2[] = {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, };
int main(void)
{
setup2();
initialization();
while(1){
// st=0x90;p1=69;p2=125;
byte note = 60;
byte note2=60;
while(Serial.available()<=12) {
}
// update the voices
phaccu_lfo += tword_lfo;
lfo_icnt = phaccu_lfo >> 8;
lfo = (pgm_read_byte(sine256+lfo_icnt)-127)/128.0f;
eg1 = eg1_rate_level[eg1_phase] + eg1_rate[eg1_phase] * eg1;
if (!eg1_phase && eg1 > 0.98) eg1_phase=1;
eg2 = eg2_rate_level[eg2_phase] + eg2_rate[eg2_phase] * eg2;
if (!eg2_phase && eg2 > 0.98) eg2_phase=1;
gain1 = (current.op1_gain<<1) + (eg1 * ((current.op1_env-64)<<1));// + keyfollow ;
if (gain1 < 0) gain1 = 0;
gain2 = (current.op2_env<<1)*eg2;
dfreq=tfreq;
tword_m1 = pow(2,32)*((dfreq* current.op1_ratio)/2 * (1+(lfo*current.op1_lfo)/256.0))/refclk;
tword_m2 = pow(2,32)*((dfreq* current.op2_ratio)/2 * (1+(lfo*current.op2_lfo)/256.0))/refclk;
phaccu_lfoB += tword_lfoB;
lfo_icntB = phaccu_lfoB >> 8;
lfoB = (pgm_read_byte_near(sine256_2+lfo_icntB)-127)/128.0f;
// lfoB = (pgm_read_byte_near(saw256+lfo_icntB)-127)/128.0f;
eg3 = eg3_rate_level[eg3_phase] + eg3_rate[eg3_phase] * eg3;
if (!eg3_phase && eg3 > 0.98) eg3_phase=1;
eg4 = eg4_rate_level[eg4_phase] + eg4_rate[eg4_phase] * eg4;
if (!eg4_phase && eg4 > 0.98) eg4_phase=1;
gain1B = (current2.op3_gain<<1) + (eg3 * ((current2.op3_env-64)<<1));// + keyfollow ;
if (gain1B < 0) gain1B = 0;
gain2B = (current2.op4_env<<1)*eg4;
//dfreq = portamento*tfreq+(1-portamento)*dfreq;
dfreq2=tfreq2;
tword_m1B = pow(2,32)*((dfreq2* current2.op3_ratio)/2 * (1+(lfoB*current2.op3_lfo)/256.0))/refclk;
tword_m2B = pow(2,32)*((dfreq2* current2.op4_ratio)/2 * (1+(lfoB*current2.op4_lfo)/256.0))/refclk;
//} THIS ONE!!!!
}
}
}
//******************************************************************
// timer2 setup
// set prscaler to 1, PWM mode to phase correct PWM, 16000000/510 = 31372.55 Hz clock
// Serial timer interrupt
//******************************************************************
// 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)
volatile int out,out2;
ISR ( TCC0_OVF_vect ) {
// internal timer
if(icnt1++ > 31) { // slightly faster than 1ms
do_update=1;
icnt1=0;
}
// operator 1
phaccu1=phaccu1+tword_m1;
icnt=phaccu1 >> 24;
y1 = pgm_read_byte_near(sine256 + ((icnt+fb1) % 256));
fb1 = fb*(y1 + fb1) >> 8;
// operator 2
phaccu2=phaccu2+tword_m2;
icnt=phaccu2 >> 24;
//fb2 = gain1*(y1) >> 8-(gain1>>1);
y2 = pgm_read_byte_near(sine256 + ((icnt+fb2)%256));
fb2 = ((gain1*y1)>>6)-(gain1>>1);
// operator 3
phaccu1B=phaccu1B+tword_m1B;
icntB=phaccu1B >> 24;
y1B = pgm_read_byte_near(sine256_2 + ((icntB+fb1B) % 256));
fb1B = fbB*(y1B + fb1B) >> 8;
// operator 4
phaccu2B=phaccu2B+tword_m2B;
icntB=phaccu2B >> 24;
//fb2 = gain1*(y1) >> 8-(gain1>>1);
fb2B = ((gain1B*y1B)>>6)-(gain1B>>1);
y2B = pgm_read_byte_near(sine256_2 + ((icntB+fb2B)%256));
// set the PWM
out = ((gain2*y2)>>8)-(gain2>>1);
out2 = ((gain2B*y2B)>>8)-(gain2B>>1);
// DC restore and clip output
out += 127;
out >>=1;
if (out<0) out=0;
if (out>0xff) out = 0xff;
out2 += 127;
out2 >>=1;
if (out2<0) out2=0;
if (out2>0xff) out2 = 0xff;
DACB.CH0DATA=(out<<4);
DACB.CH1DATA=(out2<<4);
}
It is customerry to post code that will compile. Also this is an arduino forum but that is not arduino code.