16ch Sparkfun Multiplexer Breakout Board

Projects Programming
4 
// change S0..S3 to the actual pins you use
// make sure they are least significant bit to most significant bit (S0 to S3)
const int addressPins = { S0, S1, S2, S3 };
const int analogPin = X;  // set to whatever pin you connect to
int analogValue[16];

void readAllChannels() {
  for ( int ch = 0; ch < 16; ++ch ) {
    for ( int i = 0; i < 4; ++i ) {
      digitalWrite( addressPins[i], bitRead( ch, i ) ); // set the address lines
    }
    analogValue[ch] = analogRead(analogPin);
  }
}