consul-vdx-term-keyboard-converter/terminal_keyboard_emulator.ino

#include <TimerOne.h>

// config:
const int pinData = 6;
const int pinStatus = 7;

// fixed values 
const int timerDelay = 500;

void setup(void)
{
  pinMode(pinData, OUTPUT);
  
  Timer1.initialize(timerDelay);
  Timer1.attachInterrupt(clockCycle);
  Timer1.stop();
    
  pinMode(pinStatus, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(pinStatus), statusCycle, CHANGE);
  
  Serial.begin(9600);
}

volatile long lastChange = 0;
volatile int x = 0;
volatile int dataWord = 0;
volatile int dataState = 0;
volatile int dataDelay = 0;
volatile int packetDelay = 0;
volatile int packetTail = 0;
volatile int clkState = LOW;

void statusCycle() {
  long timeNow = millis();
  long changeDiff = timeNow - lastChange;
  lastChange = timeNow;
  if (changeDiff >= 10) {
    dataWord = (0 + x);
    dataState = 8;
    dataDelay = 0;
    packetDelay = 0;
    packetTail = 100;
    x = (x + 1) % 8; 
    clkState = HIGH;
    Timer1.initialize(timerDelay);
    Timer1.start();
  }
}

void clockCycle(void)
{
  int dataBit = HIGH;
  if (clkState == LOW) {
    clkState = HIGH;
  } else {
    clkState = LOW;
  }
  if (packetDelay > 0) {
    packetDelay--;
  } else if (dataDelay > 0) {
    dataDelay--;
    dataBit = LOW;
  } else if (dataState > 0) {
    int bitToSend = (dataWord >> (dataState - 1)) & 1;
    dataBit = !bitToSend ? LOW : HIGH;
    dataState--;
  } else if (packetTail > 0) {
    packetTail--;
    dataBit = LOW;
  } else {
    Timer1.stop();
  }
  digitalWrite(pinData, dataBit);
}

void loop(void)
{
  delay(500);
  
  /*noInterrupts();
  dataWord = 0b1000000011 | (('A' + x) << 2);
  dataState = 16;
  x = (x + 1) % 30;
  interrupts();*/
}