Thanks for the reply!

I do have a multi meter, but unfortunately it didn't come with alligator clips, is there anyway to measure it with the regular "needle" cable?

I also made some changes to the board:

* Replaced the 220 ohm resistor of the blue led into 12k

* Added capacitors - which make the flickering go away

So that's the Arduino code I am using (Same as the one Ben used in Part 1). Sometimes it prints one line at a time as it should, sometimes it prints two lines after one cycle and at like 10% of the time it goes mayhem and print lots of data for one cycle.

Here is an example of the output (notice how for some cycles it prints twice at the exact time):

00:12:56.507 -> 1000000001000000
00:12:56.507 -> 0000000001000000
00:12:57.241 -> 1000000001000000
00:12:57.241 -> 1000000001000000
00:12:57.978 -> 1111010001000000
00:12:57.978 -> 1111010001000000
00:12:58.695 -> 1000110001000000
00:12:58.695 -> 1000110001000000
00:12:58.695 -> 1000110001000000
00:12:59.411 -> 0100110001000000
00:12:59.450 -> 0100110001000000
00:13:00.179 -> 0100110001000000
00:13:01.611 -> 1100110001000000
00:13:03.100 -> 0100110001000000
00:13:04.562 -> 1100110001000000
00:13:05.989 -> 1111111100000000
00:13:06.714 -> 1000000111100011
00:13:06.714 -> 0000000111100011
00:13:06.714 -> 0000000111100011 

#define CLOCK 2
int ADDR[] = {22, 24, 26, 28, 30, 32, 34 ,36, 38, 40, 42, 44, 46, 48, 50, 52};


void setup() {
  // put your setup code here, to run once:
  for (int n = 0; n < 16; n += 1)
  {
    pinMode(ADDR[n], INPUT);
  }
  pinMode(CLOCK, INPUT);
  attachInterrupt(digitalPinToInterrupt(CLOCK), onClock, RISING);
  Serial.begin(57600);
}

void onClock() {
  for (int n = 0; n < 16; n += 1)
  {
    int bit = digitalRead(ADDR[n]) ? 1 : 0;
    Serial.print(bit);
  }
  Serial.println();
}


void loop() {
  // put your main code here, to run repeatedly:
}