/*
  Title: attiny_i2c_master.ino
  Author: Lucas Lim 
  Date Created: 29/04/2019
  Last Modified: 29/04/2019
  
  Purpose: MASTER receive 'instruction' from PC via serial port (Tx, Rx)
           MASTER reply acknoledge message back to PC
           If instruction is to Slave 1/2, MASTER re-route to addressed 
              Slave 1/2 via I2C bus 
           Instruction :
             '0' MASTER will Blink LED
             '1' Slave 1 will blink LED
             '2' Slave 2 will blink LED
  NOTE! - It is important to use pullups on the SDA & SCL lines on the I2C bas!             
*/

#include <SoftwareSerial.h>
#include <TinyWireM.h>

#define slave1 (1)
#define slave2 (2)

const int ledPin = 1;   //PB1 - Arduino Pin No. 1
const int tx = 3;       //PB3 - Arduino Pin No. 3
const int rx = 4;       //PB4 - Arduino Pin No. 4
int times = 3;          //Number of times that LED will blink

SoftwareSerial mySerial(rx, tx);

void setup() {
  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);
  mySerial.println("<Serial Communication is ready>");

  // initialize the led pin as an output.
  pinMode(ledPin, OUTPUT);

  // join I2C bas as MASTER
  TinyWireM.begin();
}



void process_incoming_command(char cmd)
// Received user command from host PC via Software Serial
{
  switch (cmd)
  {
    case '0':                     // MASTER to blink led
      blink_led(times);
      break;
    case '1':                    // Slave 1 to blink led
      TinyWireM.beginTransmission(slave1);
      TinyWireM.send(times);
      TinyWireM.endTransmission();
      break;
    case '2':                   // Slave 2 to blink led
      TinyWireM.beginTransmission(slave2);
      TinyWireM.send(times);
      TinyWireM.endTransmission();
      break;
  }
}


void blink_led(int times)
{
    while(times--)
    {
        digitalWrite(ledPin, HIGH);
        delay(500);
        digitalWrite(ledPin, LOW);
        delay(500);
        
        // for debugging
        //mySerial.print("Blink times : "); 
        //mySerial.println(times); 
    }
}

void loop() {
  // don't read unless there is data, Serial.available() > 0
  if(mySerial.available())
  {
    char cmd = mySerial.read();  //User to type '0' for Master, '1' for Slave 1 and '2' for Slave 2"
    mySerial.print("You typed : ");
    mySerial.println(cmd); 
    process_incoming_command(cmd);
  }
  
  delay(50);   //limit how fast the serial check/update
}