typedef enum  {TX_IDLE, TX_DATA_BITS, TX_STOP_BITS, TX_START_BITS} tmr3ISRstate_t;

ISR(TIMER3_OVF_vect) {
    static uint8_t transmitBufferIndex = 0;
    static tmr3ISRstate_t tmr3ISRstate = TX_IDLE;
    static uint8_t tx_checksum = false;
    static uint8_t mask;
    static char letter;
        switch (tmr3ISRstate) {
            case TX_IDLE:
              if (transmitStart == true) {
// Your Code//



              }
              break;
            case TX_START_BITS:
// Your Code//



              break;             
            case TX_DATA_BITS:            
// Your Code//






              break;                
            case TX_STOP_BITS:
// Your Code//













              break;               
            default:
              tmr3ISRstate = TX_IDLE;
              TCCR5A &= ~(1 << COM5B1);
        }
// Your Code//; // 2400 Baud
}

typedef enum  {RX_IDLE, RX_DATA_BYTES, RX_CHECKSUM} myUSART1ISR_t;
//----------------------------------------------
// My EUSART2 ISR to handle incoming characters from IR decoder
//----------------------------------------------
ISR(USART1_RX_vect) {   
  static myUSART1ISR_t usart1ISRstate = RX_IDLE;
  static uint8_t receiveBufferIndex = 0;
  switch(usart1ISRstate) {
      case RX_IDLE:
          receiveBufferIndex = 0;
          receiveIRBuffer[receiveBufferIndex++] =  UDR1;        
          usart1ISRstate = RX_DATA_BYTES;
          break;          
      case RX_DATA_BYTES:            
          if ((receiveIRBuffer[receiveBufferIndex++] =  UDR1) == '\0')    
             usart1ISRstate = RX_CHECKSUM;            
          break;         
      case RX_CHECKSUM:
// Your Code//




          break;          
      default:
          usart1ISRstate = RX_IDLE;
          break;
  }
}