// Lucas Eckels
// http://lucaseckels.com

// IR remote control emitter for NEC protocol remote, as described at
// http://www.sbprojects.com/knowledge/ir/nec.htm
// Tested on a Samsung LCD TV.

#include <util/delay.h>

#define IR_PIN 13

// With CONTINOUS defined, the first command is repeated continuously until
// you reset the Arduino.  Otherwise, it sends the code once, then waits for
// another command.
#define CONTINUOUS

// Times are in microseconds
#define ON_START_TIME 4500
#define OFF_START_TIME 4500
#define ON_TIME 580
#define OFF_TIME_ONE 1670
#define OFF_TIME_ZERO 540

#define DEVICE_1 7
#define DEVICE_2 7

void setup() {
  pinMode(IR_PIN, OUTPUT);
  digitalWrite(IR_PIN, LOW);
  Serial.begin(9600);
  delay(1000);
  Serial.write("Starting up..\n");
}

byte command = 0;
int commandCount = 0;
bool commandReady = false;
void loop() {
  if (commandReady) {
    Serial.print("Writing command ");
    Serial.print(command, DEC);
    Serial.print("\n");
    
    writeStart();
    // Writing device code
    writeByte(DEVICE_1);
    writeByte(DEVICE_2);

    // Writing command code
    writeByte(command);
    writeByte(~command);
    writeEnd();
    delay(100);
    
#ifndef CONTINUOUS
    commandReady = false;
    command = 0;
    commandCount = 0;
#endif    
    return;
  }  
  
  if (Serial.available() > 0) {
    // Read in a 3-digit decimal command code.
    byte incoming = Serial.read();
    if (incoming <= '9' || incoming >= '0') {
      command *= 10;
      command += incoming - '0';
      ++commandCount;
    }
    if (commandCount == 3) {
      commandReady = true;
    }
  }
}

void writeStart() {
  modulate(ON_START_TIME);
  delayMicroseconds(OFF_START_TIME);
}

void writeEnd() {
  modulate(ON_TIME);
}

void writeByte(byte val) {
  // Starting with the LSB, write out the 
  for (int i = 0x01; i & 0xFF; i <<= 1) {
    modulate(ON_TIME);
    if (val & i) {
      delayMicroseconds(OFF_TIME_ONE);
    } else {
      delayMicroseconds(OFF_TIME_ZERO);
    }
  }  
}

void modulate(int time) {
  int count = time / 26;
  byte portb = PORTB;
  byte portbHigh = portb | 0x20; // Pin 13 is controlled by 0x20 on PORTB.
  byte portbLow = portb & ~0x20;
  for(int i = 0; i <= count; i++) {
    // The ideal version of this loop would be:
    // digitalWrite(IR_PIN, HIGH);
    // delayMicroseconds(13);
    // digitalWrite(IR_PIN, LOW);
    // delayMicroseconds(13);
    // But I had a hard time getting the timing to work right.  This approach was found
    // through experimentation.
    PORTB = portbHigh;
    _delay_loop_1(64);
    PORTB = portbLow;
    _delay_loop_1(64);
  }
  PORTB = portb;
 }