// 4x4 Matrix Keyboard Control Master

// Uses the Wire library to write LED data to the leds
// and read keypress data from the keypad
// Refer to the "Keypad I2C Slave" example for use with this sketch.

// This example code is in the public domain.

#include <Wire.h>

void setup() {
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  //Default Serial I/O 
}

byte leds = 0;     // Bit array for LED status
byte ledbit = 0;   // Bit position of LED to switch
byte state = 0;    // State of selected LED
String cmd;

void loop() {
  byte val = 0;
  // Get LED control command from User (char COMMAND char VAL HI-BYTE char VAL LO_BYTE)
  // 3 characters required!!  All Hex.
  while (Serial.available()) {
    char c = Serial.read();
    if ((c == '\n') || (c == '\r')) {
      if (cmd.length() > 2) {
        uint8_t ledbit = cmd[0] - 48; // Convert char to byte
        uint8_t state = cmd[1] - 48;
        if (state > 9) state -= 7;
        if (state > 15) state -= 32;
        uint8_t t = cmd[2] - 48;
        if (t > 9) t -= 7;
        if (t > 15) t -= 32;
        state = state * 16 + t;
        Serial.println(ledbit, HEX);
        Serial.println(state, HEX);
        Wire.beginTransmission(8);   // transmit to device #8
        Wire.write(ledbit);          // send LED number
        Wire.write(state);           // send LED state
        Wire.endTransmission();      // stop transmitting
      }
      cmd = "";
      delay(100);
    }
    else cmd += c;
  }

  // Check for key or button press.
  Wire.requestFrom(8, 2);    // request COL ROW from keypad (device #8)
  byte r;
  byte c;
  while (Wire.available()) { // peripheral may send less than requested
    r = Wire.read();
    c = Wire.read();
  }
  if (r != 0xFF) {
    // flag keypress

    Serial.print("R ");
    Serial.println(r, HEX);         // print the character
    Serial.print("C ");
    Serial.println(c, HEX);         // print the character

  }
  delay(500);
}