#include <EEPROM.h>

void setup() 
{
  Serial.begin(115200);
}

void loop() 
{
  SetSavedState( random(0,8), random(0,2));
  delay(3000);
}

// Return a byte with a random pattern.
byte functiontogetstateofrelaysfromeeprom()
{
  byte result = 0;
  for(int i=0; i<8; i++)
    bitWrite(result, i, random(0,2));
  return( result);
}

// Request the data from EEPROM and change it and send it
// Relay: 0...7
// State: 0 or 1
void SetSavedState(int Relay, int State) 
{
  // Get it
  byte myRelaysOld = functiontogetstateofrelaysfromeeprom();
  
  // Change it
  byte myRelaysNew = myRelaysOld;
  bitWrite( myRelaysNew, Relay, State);

  // Conver it to text
  char text[] = "00000000";   // must be 8 characters of 0
  for( int i=0; i<8; i++)
  {
    if( bitRead( myRelaysNew, 7-i) == 1)  // start with higest bit
      text[i] = '1';
  }

  // Print everything
  Serial.print("From EEPROM: ");
  for( int i=7; i>=0; i--)              // print zeros in front
  {
    if( bitRead( myRelaysOld, i) == 0)
      Serial.print('0');
    else
      break;
  }
  Serial.print( myRelaysOld, BIN);
  Serial.print(", Relay = ");
  Serial.print(Relay);
  Serial.print(", State = ");
  Serial.print(State);
  Serial.print(", result as text = ");
  Serial.println(text);
}