0

I'm trying to send 60 float values via serial. Numbers are provided by an accelerometer and saved in a 240 bytes-long array. The array is sent to a function and these values are then copied in a structure.

The problem The content of the array is still correct when the function is called. Then, when I copy it in the structure, something wrong happens and data are modified after the 26th float.

Where does the modification of an array of floats take place?

void sendBuffAcc(float a[])
{
  int stepCont = 1;

  // Prints the content of the globally defined array buffXAccToSend
  Serial.println();      
  for (int i=0;i<sizeBuffAcc;i++)    
  {  
    Serial.print("val: ");
    Serial.print(i);
    Serial.print("    ");
    Serial.println(buffXAccToSend[i]);
  }
  Serial.println();           

  MyShortCommand * pMyCmdShort = (MyShortCommand *)(&bufferAcc[sizeof(MyControlHdr)]);

  for (int i=0;i<sizeBuffAcc;i++)    
  {
    Serial.print("val: ");
    Serial.print(i);
    Serial.print("| Global Array:");
    Serial.println(buffXAccToSend[i]);

    numFilterValuesToSend++;    

    pMyCmdShort->cmd = accValuesID;  
    pMyCmdShort->param1 = a[i];  
    pMyCmdShort->param2 = 0;
    pMyCmdShort->param3 = 0;
    pMyCmdShort->param4 = 0;

    Serial.print("|   Param: ");
    Serial.print(pMyCmdShort->param1);
    Serial.print("|   Array:");
    Serial.println(a[i]);

    // Move the pointer to save data in next positions
    pMyCmdShort++;
  }
  stepCont++;
 }
 storeAccData = false;
 contBuffAcc=1;      
}

First, the content of the global array buffXAccToSend is printed via serial, then the i-th elements of a[i] and the value assigned to the pMyCmdShort->param1. This is the output:

val: 0    -0.00
val: 1    -0.00
val: 2    0.01
val: 3    -0.01
val: 4    0.04
val: 5    0.00
val: 6    0.01
val: 7    0.03
val: 8    0.01
val: 9    -0.00
val: 10    0.00
val: 11    -0.01
val: 12    -0.00
val: 13    0.01
val: 14    -0.02
val: 15    0.03
val: 16    0.00
val: 17    0.02
val: 18    -0.01
val: 19    0.00
val: 20    0.00
val: 21    -0.00
val: 22    -0.01
val: 23    -0.01
val: 24    0.01
val: 25    0.01
val: 26    -0.00
val: 27    0.03
val: 28    -0.01
val: 29    -0.00
val: 30    0.04
val: 31    -0.01
val: 32    0.01

val: 0| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 1| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 2| Global Array: -0.01|  Param: -0.01|  Array: -0.01
val: 3| Global Array: -0.02|  Param: -0.02|  Array: -0.02
val: 4| Global Array: 0.02|  Param: 0.02|  Array: 0.02
val: 5| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 6| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 7| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 8| Global Array: 0.04|  Param: 0.04|  Array: 0.04
val: 9| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 10| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 11| Global Array: -0.00|  Param: -0.00|  Array: -0.00
val: 12| Global Array: -0.01|  Param: -0.01|  Array: -0.01
val: 13| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 14| Global Array: -0.02|  Param: -0.02|  Array: -0.02
val: 15| Global Array: -0.02|  Param: -0.02|  Array: -0.02
val: 16| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 17| Global Array: -0.02|  Param: -0.02|  Array: -0.02
val: 18| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 19| Global Array: 0.03|  Param: 0.03|  Array: 0.03
val: 20| Global Array: -0.01|  Param: -0.01|  Array: -0.01
val: 21| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 22| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 23| Global Array: 0.01|  Param: 0.01|  Array: 0.01
val: 24| Global Array: -0.01|  Param: -0.01|  Array: -0.01
val: 25| Global Array: -0.02|  Param: -0.02|  Array: -0.02
val: 26| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 27| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 28| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 29| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 30| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 31| Global Array: 0.00|  Param: 0.00|  Array: 0.00
val: 32| Global Array: 0.00|  Param: 0.00|  Array: 0.00

This is the output of avr-size:

   text    data     bss     dec     hex
  55828    3906    2978   62712    f4f8

Is it a memory related problem?

  • What does avr-size say about the final executable? – Ignacio Vazquez-Abrams Nov 25 '14 at 22:37
  • @IgnacioVazquez-Abrams Please see the output of the command – UserK Nov 25 '14 at 23:20
  • Are you doing any dynamic memory allocations? can you post the full code? – Omer Jan 25 '15 at 13:41
  • 1
    Please post a Minimal, Complete, and Verifiable example. Not seeing the data declarations, nor the value of sizeBuffAcc it is impossible to tell what the issue is. – Nick Gammon Aug 24 '15 at 21:51
1

The ATmega328P has 2kiB of SRAM. Your program uses almost 3kiB. Move strings and constant values into flash.

  • Thanks for the suggestion but I'm using the Mega 2560 which has 8KB of SRAM. – UserK Nov 26 '14 at 13:00
  • I will modify the sketch with PROGMEM as you suggested. – UserK Nov 26 '14 at 15:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.