memcpy

Projects Programming
1

I have an issue with some code.
When I try to compile this:

#include <avr/interrupt.h>
#include <string.h>
#define AXIS_X 1
#define AXIS_Y 2
#define AXIS_Z 3

int CUBE_SIZE = 8;
int CUBE_BYTES = 64;
volatile byte cube[8][8];
volatile int current_layer = 0;

void setup()
{
  int i;
  
  for(i=0; i<14; i++)
    pinMode(i, OUTPUT);
  
  // pinMode(A0, OUTPUT) as specified in the arduino reference didn't work. So I accessed the registers directly.
  DDRC = 0xff;
  PORTC = 0x00;
  
  // Reset any PWM configuration that the arduino may have set up automagically!
  TCCR2A = 0x00;
  TCCR2B = 0x00;

  TCCR2A |= (0x01 << WGM21); // CTC mode. clear counter on TCNT2 == OCR2A
  OCR2A = 10; // Interrupt every 25600th cpu cycle (256*100)
  TCNT2 = 0x00; // start counting at 0
  TCCR2B |= (0x01 << CS22) | (0x01 << CS21); // Start the clock with a 256 prescaler
  
  TIMSK2 |= (0x01 << OCIE2A);
}

ISR (TIMER2_COMPA_vect)
{
  int i;
  
  // all layer selects off
  PORTC = 0x00;
  PORTB &= 0x0f;
  
  PORTB |= 0x08; // output enable off.
  
  for (i=0; i<8; i++)
  {
    PORTD = cube[current_layer][i];
    PORTB = (PORTB & 0xF8) | (0x07 & (i+1));
  }
  
  PORTB &= 0b00110111; // Output enable on.
  
  if (current_layer < 6)
  {
    PORTC = (0x01 << current_layer);
  } else if (current_layer == 6)
  {
    digitalWrite(12, HIGH);
  } else
  {
    digitalWrite(13, HIGH);
  }
  
  current_layer++;
  
  if (current_layer == 8)
    current_layer = 0;
}

void loop()
{
  int i,x,y,z;
  
  while (true)
  {
    
    effect_planboing(AXIS_Z, 400);
   
  }
}

// Flip the cube 180 degrees along the y axis.
void mirror_y (void)
{
    unsigned char buffer[CUBE_SIZE][CUBE_SIZE];
    unsigned char x,y,z;

    memcpy(buffer, cube, CUBE_BYTES); // copy the current cube into a buffer.

    fill(0x00);
    for (z=0; z<CUBE_SIZE; z++)
    {
        for (y=0; y<CUBE_SIZE; y++)
        {
            for (x=0; x<CUBE_SIZE; x++)
            {
                if (buffer[z][y] & (0x01 << x))
                    setvoxel(x,CUBE_SIZE-1-y,z);
            }
        }
    }

}

I get this error:

ledcube8x8x8.cpp: In function 'void mirror_y()':
ledcube8x8x8:87: error: invalid conversion from 'volatile void*' to 'const void*'
ledcube8x8x8:87: error: initializing argument 2 of 'void* memcpy(void*, const void*, size_t)'

Since 'cube' and 'current_layer' are also used and modified in the ISR they need to be volatile.
If I ommit the volatile statement, the sketch compiles just fine..

Any ideas?

TIA,

ReSi

2

Have you tried a simple cast?

memcpy(buffer, (char *)cube, CUBE_BYTES);

3

I have now. and it compiles!
I had a feeling it had something to do with a pointer, but didn't really find anything in the reference.

Thanks for your help !