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Converting a byte to an array and vice-versa

2010 April 18
by Tedb0t

Here are two super-useful Arduino utility functions I just devised for my thesis:

byte arrayToByte(int arr[], int len){
  // Convert -1 to 0 and pack the array into a byte
  int i;
  byte result = 0;

  for(i=len-1; i>=0; i--){
    if(arr[i] == -1){
      result &= ~(0 << i);
    } else {
      result |= (1 << i);
  return result;
int* byteToArray(byte in){
  int i, temp, out[8];

  for(i=0; i<8; i++){     temp = (in >> i) & 1;
    if(temp == 0) temp = -1;
    out[i] = temp;
  return out;

The first function takes in an array of up to 8 integers valued 1 or -1 and generates a corresponding byte; the second does the reverse.  Easy to modify for other integer values.

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