const int statePin = 3;     // Connect LattePanda's S3 pin to Arduino's D3
const int resetPin = 4;     // Connect LattePanda's RST pin to Arduino's D4
const int D10      = 10;
const int D11      = 11;
const int D12      = 12;
 
bool          watchdogActive = false;
unsigned long lastReceivedTime;
unsigned long currentTime;

bool          lastLEDState = LOW;
unsigned long lastLEDTime;
unsigned long currentLEDTime;
 
void setup() 
{
  pinMode(LED_BUILTIN, OUTPUT);

  digitalWrite (LED_BUILTIN, LOW);
  lastLEDTime = millis ();
  
  pinMode(statePin, INPUT); // Set as input to read the state pin's level
  pinMode(resetPin, INPUT); // By default, the RST pin on LattePanda is 3.3V. Initialize Arduino pin as INPUT to match this level.

  pinMode(D10, OUTPUT);
  pinMode(D11, OUTPUT);
  pinMode(D12, OUTPUT);
    
  Serial.begin(9600);
}
 
void loop() 
{ 
  //-- Check to see if it's time to change the LED state.
  currentLEDTime = millis ();
  if (currentLEDTime > lastLEDTime) //-- Check for millis overflow
  {
    if (currentLEDTime - lastLEDTime > 1000U)
    {
      if (lastLEDState == LOW)
      {
        digitalWrite (LED_BUILTIN, HIGH);
        lastLEDState = HIGH;
      }
      else
      {
        digitalWrite (LED_BUILTIN, LOW);
        lastLEDState = LOW;  
      }
    
      lastLEDTime = millis ();
    }
  }
  else
    lastLEDTime = currentLEDTime;
     
  // Check if the watchdog should be activated
  if (digitalRead (statePin) == HIGH)
  {
    if (Serial.available () > 0) 
    {
      char receivedChar = Serial.read ();
      if (receivedChar == 'A') 
      {
        watchdogActive = true;
        lastReceivedTime = millis();
      }
      else if (receivedChar == 'Q') 
      {
        watchdogActive = false;
      }
      else if (receivedChar == '0')
      {
        digitalWrite (D10, LOW);
        digitalWrite (D11, LOW);
        digitalWrite (D12, LOW);
      }
      else if (receivedChar == '1')
      {
        digitalWrite (D10, LOW);
        digitalWrite (D11, LOW);
        digitalWrite (D12, LOW);

        digitalWrite (D10, HIGH);
      }
      else if (receivedChar == '2')
      {
        digitalWrite (D10, LOW);
        digitalWrite (D11, LOW);
        digitalWrite (D12, LOW);

        digitalWrite (D11, HIGH);
      }
      else if (receivedChar == '3')
      {
        digitalWrite (D10, LOW);
        digitalWrite (D11, LOW);
        digitalWrite (D12, LOW);

        digitalWrite (D10, HIGH);
        digitalWrite (D11, HIGH);
      }
      else if (receivedChar == '4')
      {
        digitalWrite (D10, LOW);
        digitalWrite (D11, LOW);
        digitalWrite (D12, LOW);

        digitalWrite (D12, HIGH);
      }
    }
  } 
  else 
  {
    watchdogActive = false;
  }

  // If watchdog is active and 's' character isn't received within 1 minute, reboot LattePanda board
  currentTime = millis ();
  if (currentTime > lastReceivedTime) //-- Check for millis overflow and wait for the next cycle if it has
  {  
    if (watchdogActive && (currentTime - lastReceivedTime > 60000U))
    {
      pinMode(resetPin,OUTPUT);     // Set pin to OUTPUT mode
      digitalWrite(resetPin, LOW);  // Pull down the RST pin to reboot the LattePanda board
      delay(50);                    // Maintain a LOW level for 50ms
      pinMode(resetPin, INPUT);     // Set pin back to INPUT mode to match default 3.3V level of LattePanda's RST pin
      watchdogActive = false;       // Stop the watchdog function after rebooting the LattePanda board
    }
  }
}