// This is all happening within an Object and scanLine is a method
uint8_t scanwidth = 64;
uint8_t sections = 32;
NUMBYTES = scanwidth * sections * 4;
matrixbuff = (uint32_t *)malloc(NUMBYTES);
memset(matrixbuff, 255, NUMBYTES); // I set it to all white, just to make sure...

void scanLine() {
  uint32_t *matrixptr;
  uint8_t i, j;
  matrixbuff[0] = 0xFFFFFFFF; // I only use the first entry for testing purpose, enough for every 5th column

  for (j=0; j<31; j++){
      for ( i=0; i<scanwidth/5; i++) {
          matrixbuff[0] = 0xFFFFFFFF; // When I comment this line out, the screen flickers!
          matrixptr = matrixbuff;
          data = *matrixptr++; // Again, I only use matrixbuff[0] for testing purpose
          /*
          ...
          ...
          */
          }
      }
  }