Teensy2.0++ Progmem>53% corrupting USB functionality

GrZl · Apr 5, 2020

Hello,

i am porting a common license PWM-sample-drumbox to teensy2++ over teensyduino/teensy loader V1.51. The project reads 8bit array values from Progmem into a ringbuffer and generates audio with hardware PWM. Everything is working perfect, the code occupies about 12% of progmem, 8% ram.

Now i fill more and more program memory with these audio-sample arrays for having more audiosamples to play. From a certain point of used program memory - somewhere around 53% - i get a problem: after flashing over usb (and the rebooting display in the loader), windows loses the USB device and the project does not work anymore. I have to replug USB with the button pressed down and flash a smaller project first until the teensy2.0++ will be recognized by USB and working properly again.

To me it looks like a program occupying more than 53% starts to 'overwrite' parts of the bootloader/USB driver. Having written bootloaders myself (for flashing firmwares over UART/MIDI) i doubt the usb/flashing functionality occupies nearly 50%/64k of the progmem.

If someone please could give me a hint what might be wrong, most probably i misunderstood something essential about the teensy/usb flashing concept?

thanks in advance
Gregor

defragster · Apr 5, 2020

Not used T_2's family - but Paul's bootloader is called 'HalfKay' - and expect whatever space it uses is accounted for in 'available' resources.

The Teensy family uses MCU's with onboard USB - not an external UART<>USB chip. So when the code crashes the USB stack fails … if it is like the T_3 and later ARM units.

Common cause there is that some memory corruption from a bad pointer or other code problem that doesn't hit anything under 53% hits something essential as additional resources are consumed.

As samples are read and acted on guess would be errant pointer or indexing or loading of subsequent additional samples, or a larger or ill formed sample read?

Without T_2 history and no code to see that is just typical speculation ...

larry_berlin · Apr 5, 2020

Hello,

according forum rules please post your code. Here are a lot of people wich are able to point you in the right direction if code shown.

My blind guess is, you have function calls wich use a lot of heap (maybe you have local arrays in your code or so).

GrZl · Apr 6, 2020

Code:

// dsp-L8 Latin Perc Chip (c) DSP Synthesizers 2015
// Free for non commercial use
// http://janostman.wordpress.com

// modified by G.Zoll, 04/2020 for miditrigger, multiple kits, teensy2++, ...

#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <MIDI.h>

#include "samples_909.h"      // 1-8
#include "samples_MiniPops.h" // 9-16 selected by 9 to GND
#include "samples_latin.h"    // 17-24 selected by 10 to GND
 

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


#define digitalReadFast(P) bitRead(*digitalPinToPINReg(P), digitalPinToBit(P))                  
#define digitalWriteFast(P, V) bitWrite(*digitalPinToPortReg(P), digitalPinToBit(P), (V))

const unsigned char PS_128 = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);

int led = 6;

MIDI_CREATE_INSTANCE(HardwareSerial, Serial1, MIDI);

// arrays with 8 sample lenghts sorted by kits

uint16_t smpLength1[3] = {SampleLength1, SampleLength9, SampleLength17};
uint16_t smpLength2[3] = {SampleLength2, SampleLength10, SampleLength18};
uint16_t smpLength3[3] = {SampleLength3, SampleLength11, SampleLength19};
uint16_t smpLength4[3] = {SampleLength4, SampleLength12, SampleLength20};
uint16_t smpLength5[3] = {SampleLength5, SampleLength13, SampleLength21};
uint16_t smpLength6[3] = {SampleLength6, SampleLength14, SampleLength22};
uint16_t smpLength7[3] = {SampleLength7, SampleLength15, SampleLength23};
uint16_t smpLength8[3] = {SampleLength8, SampleLength16, SampleLength24};


//--------- Ringbuf parameters ----------
uint8_t Ringbuffer[256];
uint8_t RingWrite=0;
uint8_t RingRead=0;
volatile uint8_t RingCount=0;
volatile uint16_t SFREQ;
//-----------------------------------------

ISR(TIMER1_COMPA_vect) {
  
    //-------------------  Ringbuffer handler -------------------------
    
    if (RingCount) {                            //If entry in FIFO..
      OCR2A = Ringbuffer[(RingRead++)];          //Output LSB of 16-bit DAC
      RingCount--;
    }
    
    //-----------------------------------------------------------------
}

void setup() {
  
    OSCCAL=0xFF;
        
    //8-bit PWM DAC pin
    pinMode(24, OUTPUT);

    // inputs for selection of kits
    pinMode(PIN_E0,INPUT_PULLUP);  // E0
    pinMode(PIN_E1,INPUT_PULLUP);  // E1
    

    //_______________________________________________ Set up Timer 1 to send a sample every interrupt.
    cli();
    // Set CTC mode
    // Have to set OCR1A *after*, otherwise it gets reset to 0!
    TCCR1B = (TCCR1B & ~_BV(WGM13)) | _BV(WGM12);
    TCCR1A = TCCR1A & ~(_BV(WGM11) | _BV(WGM10));    
    // No prescaler
    TCCR1B = (TCCR1B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);
    // Set the compare register (OCR1A).
    // OCR1A is a 16-bit register, so we have to do this with
    // interrupts disabled to be safe.
    //OCR1A = F_CPU / SAMPLE_RATE; 
    // Enable interrupt when TCNT1 == OCR1A
    TIMSK1 |= _BV(OCIE1A);   
    sei();
    
    //OCR1A = 200; //was '400' for 40KHz Samplefreq

    // _______________________________________________Set up Timer 2 to do pulse width modulation on D11

    // Use internal clock (datasheet p.160)
    ASSR &= ~(_BV(EXCLK) | _BV(AS2));

    // Set fast PWM mode  (p.157)
    TCCR2A |= _BV(WGM21) | _BV(WGM20);
    TCCR2B &= ~_BV(WGM22);

    // Do non-inverting PWM on pin OC2A (p.155)
    // On the Arduino this is pin 11.
    TCCR2A = (TCCR2A | _BV(COM2A1)) & ~_BV(COM2A0);
    TCCR2A &= ~(_BV(COM2B1) | _BV(COM2B0));
    // No prescaler (p.158)
    TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);

    // Set initial pulse width to the first sample.
    //OCR2A = 128;

    //_______________________________________________set timer0 interrupt at 61Hz
    /*  UNUSED
    TCCR0A = 0;// set entire TCCR0A register to 0
    TCCR0B = 0;// same for TCCR0B
    TCNT0  = 0;//initialize counter value to 0
    // set compare match register for 62hz increments
    OCR0A = 255;// = 61Hz
    // turn on CTC mode
    TCCR0A |= (1 << WGM01);
    // Set CS01 and CS00 bits for prescaler 1024
    TCCR0B |= (1 << CS02) | (0 << CS01) | (1 << CS00);  //1024 prescaler 

    TIMSK0=0;
    */

    // _______________________________________________set up the ADC
    SFREQ=analogRead(0);
    ADCSRA &= ~PS_128;  // remove bits set by Arduino library
    // Choose prescaler PS_128.
    ADCSRA |= PS_128;
    ADMUX = 64;
    sbi(ADCSRA, ADSC);

    // midi
      // Initialise MIDI
    MIDI.begin(MIDI_CHANNEL_OMNI);
    MIDI.setThruFilterMode(midi::Thru::Off);
  
    // Initialise MIDI message handlers
    MIDI.setHandleNoteOff(midiNoteOffHandler);
    MIDI.setHandleNoteOn(midiNoteOnHandler);
    //MIDI.setHandleControlChange(midiControlHandler);
         
}

  uint8_t phaccAG,phaccCA,phaccMA,phaccWH,phaccTI,phaccCH,phaccQU,phaccBO;
  uint8_t pitchAG=32;
  uint8_t pitchCA=64;
  uint8_t pitchMA=64;
  uint8_t pitchWH=32;
  uint8_t pitchTI=64;
  uint8_t pitchCH=16;
  uint8_t pitchQU=16;
  uint8_t pitchBO=64;
  uint16_t samplecntSMP1,samplecntSMP2,samplecntSMP3,samplecntSMP4,samplecntSMP5,samplecntSMP6,samplecntSMP7,samplecntSMP8;
  uint16_t samplepntSMP1,samplepntSMP2,samplepntSMP3,samplepntSMP4,samplepntSMP5,samplepntSMP6,samplepntSMP7,samplepntSMP8;

  uint8_t samplKit = 0;
  
void loop() {  
  
  int16_t total;
  uint8_t divider = 0;
  uint8_t MUX=0;
  
  while(1) { 
    
     MIDI.read();

    samplKit = 0;
    if (!digitalRead(PIN_E0))  samplKit = 1;
    if (!digitalRead(PIN_E1))  samplKit = 2; 

    //------ Add current sample word to ringbuffer FIFO --------------------  
        
    if (RingCount<255) {  //if space in ringbuffer
      total=0;
        if (samplecntSMP1) {
            phaccAG+=pitchAG;
            if (phaccAG & 128) {
                phaccAG &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL1 + samplepntSMP1)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL9 + samplepntSMP1)-128);
                    break;  
                  case 2:
                    //total+=(pgm_read_byte_near(SMPL17 + samplepntSMP1)-128);
                    total+=(pgm_read_byte_near(SMPL17 + samplepntSMP1)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL1 + samplepntSMP1)-128);
                samplepntSMP1++;
                samplecntSMP1--;                
            }
      }
      if (samplecntSMP2) {
            phaccBO+=pitchBO;
            if (phaccBO & 128) {
                phaccBO &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL2 + samplepntSMP2)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL10 + samplepntSMP2)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL18 + samplepntSMP2)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL2 + samplepntSMP2)-128);
                samplepntSMP2++;
                samplecntSMP2--;                
            }
      }
       if (samplecntSMP3) {
            phaccMA+=pitchMA;
            if (phaccMA & 128) {
                phaccMA &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL3 + samplepntSMP3)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL11 + samplepntSMP3)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL19 + samplepntSMP3)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL3 + samplepntSMP3)-128);
                samplepntSMP3++;
                samplecntSMP3--;
                
            }
      }
       if (samplecntSMP4) {
            phaccQU+=pitchQU;
            if (phaccQU & 128) {
                phaccQU &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL4 + samplepntSMP4)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL12 + samplepntSMP4)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL20 + samplepntSMP4)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL4 + samplepntSMP4)-128);
                samplepntSMP4++;
                samplecntSMP4--;
                
            }
      }
       if (samplecntSMP5) {
            phaccCA+=pitchCA;
            if (phaccCA & 128) {
                phaccCA &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL5 + samplepntSMP5)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL13 + samplepntSMP5)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL21 + samplepntSMP5)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL5 + samplepntSMP5)-128);
                samplepntSMP5++;
                samplecntSMP5--;
                
            }
      }    
      if (samplecntSMP6) {
            phaccTI+=pitchTI;
            if (phaccTI & 128) {
                phaccTI &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL6 + samplepntSMP6)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL14 + samplepntSMP6)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL22 + samplepntSMP6)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL6 + samplepntSMP6)-128);
                samplepntSMP6++;
                samplecntSMP6--;
                
            }
      }  
      if (samplecntSMP7) {
            phaccWH+=pitchWH;
            if (phaccWH & 128) {
                phaccWH &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL7 + samplepntSMP7)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL15 + samplepntSMP7)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL23 + samplepntSMP7)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL7 + samplepntSMP7)-128);
                samplepntSMP7++;
                samplecntSMP7--;
                
            }
      }  
      if (samplecntSMP8) {
            phaccCH+=pitchCH;
            if (phaccCH & 128) {
                phaccCH &= 127;
                switch (samplKit) {
                  case 0:
                    total+=(pgm_read_byte_near(SMPL8 + samplepntSMP8)-128);
                    break;
                  case 1:
                    total+=(pgm_read_byte_near(SMPL16 + samplepntSMP8)-128);
                    break;  
                  case 2:
                    total+=(pgm_read_byte_near(SMPL24 + samplepntSMP8)-128);
                    break;                  
                }
                //total+=(pgm_read_byte_near(SMPL8 + samplepntSMP8)-128);
                samplepntSMP8++;
                samplecntSMP8--;
                
            }
      }  
      
      total>>=1;    // divide by 2      
      // if (!(PINB&4)) total>>=1;      // noisegate?
      total+=128;  // make it centered audiowave      
     
      if (total>255) total=255;     // total is int16, truncating to 255 makes sense.

      // noisegate
      //uint16_t accSum = samplecntSMP1+samplecntSMP2+samplecntSMP3+samplecntSMP4+samplecntSMP5+samplecntSMP6+samplecntSMP7+samplecntSMP8;
      //if (accSum==0) total = 0;
      
      cli();
      Ringbuffer[RingWrite]=total;
      RingWrite++;
      RingCount++;
      sei();
    }

//----------------------------------------------------------------------------

//----------------- Handle Triggers ------------------------------
/*

        if (PIND&4) {
          samplepntSMP2=0;
          samplecntSMP2=1474;
        }
        if (PIND&8) {
          samplepntAG=0;
          samplecntAG=1720;
        }
        if (PIND&16) {
          samplepntTI=0;
          samplecntTI=3680;
        }
        if (PIND&32) {
          samplepntQU=0;
          samplecntQU=6502;
        }
        if (PIND&64) {
          samplepntMA=0;
          samplecntMA=394;
        }
        if (PIND&128) {
          samplepntCH=0;
          samplecntCH=5596;
        }

        if (PINB&1) {
          samplepntCA=0;
          samplecntCA=2174;
        }
         if (PINB&2) {
          samplepntWH=0;
          samplecntWH=2670;
        }
        */
 

//-----------------------------------------------------------------

//--------------- ADC block -------------------------------------

  if (!(divider++)) {
    if (!(ADCSRA & 64)) {

      uint16_t pitch=((ADCL+(ADCH<<8))>>3)+1;
      //if (MUX==0) pitchAG=pitch;
      //if (MUX==1) pitchTI=pitch;
      //if (MUX==2) pitchQU=pitch;
      if (MUX==3) {
        pitchAG=pitch;
        pitchTI=pitch;
        pitchQU=pitch;
        pitchMA=pitch;
        pitchCH=pitch;
        pitchWH=pitch;        
        pitchCA=pitch;
        pitchBO=pitch;      
      }
      //if (MUX==4) pitchCH=pitch;
      //if (MUX==5) pitchWH=pitch;

      MUX++;
      if (MUX==6) MUX=0;
      ADMUX = 64 | MUX; //Select MUX
      sbi(ADCSRA, ADSC); //start next conversation
    }
  }
  
//---------------------------------------------------------------
  
  } 
}
/*  MIDI HANDLERS  */
void midiNoteOnHandler(byte channel, byte note, byte velocity) {
  digitalWrite(led, HIGH);
  handleMIDINOTE(0x90, note, 127);
}

void midiNoteOffHandler(byte channel, byte note, byte velocity) {
  digitalWrite(led, LOW);
  handleMIDINOTE(0x80, note, 0);
}

void midiControlHandler(byte channel, byte number, byte value) {
  if (number==1) {
    pitchAG=value;
    pitchTI=value;
    pitchQU=value;
    pitchMA=value;
    pitchCH=value;
    pitchWH=value;    
    pitchCA=value;
    pitchBO=value;
  }
}

void handleMIDINOTE(uint8_t message, uint8_t note, uint8_t vel) {
  
  if ((!vel) && (message == 0x90)) message = 0x80;
  if (message == 0x80) {
    
  }
  if (message == 0x90) {
      if (note==36) {
          samplepntSMP1=0;
          //samplecntSMP1=SampleLength1;//1474;
          samplecntSMP1= smpLength1[samplKit];
        }
        if (note==37) {
          samplepntSMP2=0;
          //samplecntSMP2=SampleLength2;
          samplecntSMP2= smpLength2[samplKit];
        }
        if (note==38) {
          samplepntSMP3=0;
          //samplecntSMP3=SampleLength3;
          samplecntSMP3= smpLength3[samplKit];
        }
        if (note==39) {
          samplepntSMP4=0;
          //samplecntSMP4=SampleLength4;
          samplecntSMP4= smpLength4[samplKit];
        }
        if (note==40) {
          samplepntSMP5=0;
          //samplecntSMP5=SampleLength5;
          samplecntSMP5= smpLength5[samplKit];
        }
        if (note==41) {
          samplepntSMP6=0;
          samplecntSMP6=SampleLength6;
          samplecntSMP6= smpLength6[samplKit];
        }

        if (note==42) {
          samplepntSMP7=0;
          //samplecntSMP7=SampleLength7;
          samplecntSMP7= smpLength7[samplKit];
        }
         if (note==43) {
          samplepntSMP8=0;
          //samplecntSMP8=SampleLength8;
          samplecntSMP8= smpLength8[samplKit];
        }
   
  }
}

example for one of the 8 arrays per drumkit in the external headers:

Code:

#define SampleLength11 752  // CONGA & CLAVE
const unsigned char SMPL11[SampleLength11] PROGMEM =
{
  125,82,65,93,135,172,181,161,118,74,48,54,88,139,184,207,199,166,124,92,86,109,150,192,217,215,187,146,108,90,100,130,166,191,194,171,132,93,68,68,90,123,151,160,147,115,80,54,50,68,100,132,150,147,125,96,72,66,80,111,144,167,172,158,133,109,99,107,132,162,186,194,183,159,132,116,116,131,156,177,185,176,152,124,103,96,105,125,144,154,149,130,104,83,74,80,
  98,119,134,135,123,103,84,76,81,99,122,141,148,142,127,111,102,105,121,142,161,171,168,154,137,125,123,133,149,166,175,172,158,139,123,116,119,131,145,153,151,138,120,104,94,95,105,119,129,130,123,108,94,86,87,98,113,126,132,130,120,109,102,103,113,129,143,152,152,144,134,126,125,131,143,156,164,164,156,144,133,127,130,137,147,153,152,144,131,119,111,110,115,124,130,131,125,115,103,96,
  96,101,111,120,124,122,116,108,102,102,109,120,130,137,139,134,128,123,122,128,137,147,153,155,150,143,136,133,134,140,147,152,152,147,138,129,123,122,125,130,134,134,130,122,113,107,105,108,114,120,122,120,115,109,104,104,108,115,123,128,129,126,122,119,119,123,130,138,144,145,143,139,135,133,135,140,146,150,150,147,141,135,131,130,132,136,138,138,134,128,121,116,115,116,119,122,123,121,117,112,
  108,107,110,114,119,123,123,121,118,116,116,119,125,131,135,137,136,133,131,131,133,137,142,145,146,145,141,137,135,135,136,139,141,141,138,133,128,124,123,123,125,127,127,124,121,116,113,112,113,116,119,120,120,119,116,114,115,117,121,125,129,130,130,128,127,127,130,133,137,140,142,141,139,137,135,136,138,140,142,141,140,136,133,130,129,129,130,131,130,128,125,121,118,117,117,119,120,121,120,118,
  116,115,115,116,119,122,124,125,125,124,123,124,126,129,132,135,136,136,135,134,134,135,137,139,140,140,139,137,135,133,132,133,133,134,133,131,129,126,123,122,122,122,123,123,122,120,118,116,116,117,118,120,122,122,122,121,121,121,123,125,128,130,131,131,131,131,131,132,134,136,138,138,138,136,135,134,134,134,135,135,135,133,131,129,127,126,126,126,126,125,124,122,121,119,118,119,119,120,121,121,
  120,120,119,120,121,122,124,126,127,127,127,127,128,129,131,133,134,135,135,134,134,134,134,135,135,136,135,135,133,132,130,129,129,129,129,128,127,125,124,122,121,121,121,122,122,121,121,120,119,119,120,121,122,123,124,124,124,125,125,127,128,130,131,132,132,132,132,132,133,134,135,135,135,135,134,133,132,132,131,131,131,130,129,128,127,125,125,124,124,124,124,123,122,121,120,120,121,121,122,122,
  123,123,123,123,124,125,126,127,128,129,129,130,130,130,131,132,133,134,134,134,133,133,133,133,133,133,132,132,131,130,129,128,127,127,127,126,126,125,124,123,122,122,122,122,122,123,123,122,122,122,123,123,124,125,126,127,127,127,128,128,129,130,131,132,132,132,132,132,132,132,133,133,133,132,132,131,130,130,129,129,129,128,128,127,127,126,125,125,125,125,125,125,125,124,124,124,124,125,125,126,
  126,126,126,127,127,127,128,128,129,129,129,129,129,129,129,130,130,130,130,130,130,130,129,129,129,129,129,129,128,128,128,128,128,128,127,127,127,127,127,127,127,127,127,127,127,128,128,128,128,128,128,128,128,128,128,128,
};

pdaehne · Apr 6, 2020

Hello Gregor,

when you're getting over 53% of flash memory, you're getting over the 64kb border, which means your address pointers are three bytes instead of two. I just had a quick look over your code, but it seems that you use the "pgm_read_byte_near()" macro to read your samples, which takes only a two byte address (as the "_near" suffix implies). Try to use the "pgm_read_byte_far()" macro instead.

Bye,

Patrick

defragster · Apr 6, 2020

These start 0:

Code:

uint8_t RingWrite=0;
uint8_t RingRead=0;

>> the RingWrite++ only increments with no checks to wrap to 0 when > 255 for indexing into :: Ringbuffer[256];

>> the ISR can reduce RingCount:

Code:

    if (RingCount) {                            //If entry in FIFO..
      OCR2A = Ringbuffer[(RingRead++)];          //Output LSB of 16-bit DAC
      RingCount--;
    }

>> That shows too where RingRead++ is incremented - it is never decremented or set to zero when it wraps >255

Both of those will run through memory off the end of the Ringbuffer[256]; array without bounding checks - it is not a Ring buffer but a list that grows to the end of RAM.

To be a usable Ring both when '++' - each in one spot need to have a test : if ( RingXXX>255 ) RingXXX = 0;

larry_berlin · Apr 6, 2020

defragster said:
These start 0:

Code:

uint8_t RingWrite=0; uint8_t RingRead=0;

>> the RingWrite++ only increments with no checks to wrap to 0 when > 255 for indexing into :: Ringbuffer[256];

>> the ISR can reduce RingCount:

Code:

if (RingCount) { //If entry in FIFO.. OCR2A = Ringbuffer[(RingRead++)]; //Output LSB of 16-bit DAC RingCount--; }

>> That shows too where RingRead++ is incremented - it is never decremented or set to zero when it wraps >255

Both of those will run through memory off the end of the Ringbuffer[256]; array without bounding checks - it is not a Ring buffer but a list that grows to the end of RAM.

To be a usable Ring both when '++' - each in one spot need to have a test : if ( RingXXX>255 ) RingXXX = 0;

You're right.
But the following question, if the variables are defined as uint8_t, will they not automatically return to 0 at 255++?

GrZl · Apr 6, 2020

defragster said:
>> the RingWrite++ only increments with no checks to wrap to 0 when > 255 for indexing into :: Ringbuffer[256];
>> That shows too where RingRead++ is incremented - it is never decremented or set to zero when it wraps >255

being a uint8_t ... i thought wrapping>255 automatically resets it to 0? how can it ever exceed 255?

GrZl · Apr 6, 2020

pdaehne said:
Hello Gregor,

when you're getting over 53% of flash memory, you're getting over the 64kb border, which means your address pointers are three bytes instead of two. I just had a quick look over your code, but it seems that you use the "pgm_read_byte_near()" macro to read your samples, which takes only a two byte address (as the "_near" suffix implies). Try to use the "pgm_read_byte_far()" macro instead.

Bye,

Patrick

Thank you Patrick, i will check that.

defragster · Apr 6, 2020

GrZl said:
being a uint8_t ... i thought wrapping>255 automatically resets it to 0? how can it ever exceed 255?

Correct,it should ...Too used to 32 bit to read the code I posted …

>I posted this and somehow clicked the 'delete' … restored

Teensy2.0++ Progmem>53% corrupting USB functionality

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