/*
 Based on "Jeti Box Communication for Arduino Mini Pro 328 16MHz" by Alexander Buschek
 Modified and stripped down to minimal functions by sceak

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 any later version. see <http://www.gnu.org/licenses/>
 */

#define TX_COMPLETE (1<<TXC0)
#define GETCHAR_TIMEOUT_ms 20  // 20ms timeout for Getchar Routine, just to make sure. Never ran into timeout

void JetiUartInit(void) {
  // USART initialization 16MHz, if running on other bards make sure to set UBRR0H and UBRR0L accordingly to 9600 baud
  // Communication Parameters: 9 Data, 1 Stop, Odd Parity
  // USART Receiver: On
  // USART Transmitter: On
  // USART0 Mode: Asynchronous
  // USART Baud Rate: 9600
  UCSR0A=0x00;
  UCSR0B=0x1C;
  UCSR0C=0x36;
  UBRR0H=0x00;
  UBRR0L=0x67;
}

// Transmits one byte to the box, specify if bit 9 will be set or not 
void JetiTransmitByte(unsigned char data, boolean setBit9)
{
  if (setBit9 == true)
    UCSR0B |= (1<<TXB80); // Set Bit 9
  else
    UCSR0B &= ~(1<<TXB80);    //delete 9th Bit
  /* Put data into buffer, sends the data */
  UDR0 = data;
  while ((UCSR0A & TX_COMPLETE)==0); //wait for TX complete
  UCSR0A |= TX_COMPLETE; //clear TXC Flag
}

// Read the ack from the box
unsigned char JetiGetChar(void)
{
  unsigned long time = millis();
  // Wait for data to be received
  while ( (UCSR0A & (1<<RXC0)) == 0 )
  {
    if (millis()-time >  GETCHAR_TIMEOUT_ms) 
      return 0; // return, if timout occures
  }
  return UDR0;
}

// write entire frame to the box including two lines of information (à 16 characters) plus alarm code (letter A-Z)
unsigned char JetiSensor(char line1[17], char line2[17], char alarmCode, boolean sendExitSeqence)
{
  unsigned char ack;
  int i;
  
  // result of the last frame to allow the boy some time to send the answer
  ack = JetiGetChar();
  
  UCSR0B &= ~(1<<RXEN0);  //disable RX (just to make sure)
  UCSR0B |= (1<<TXEN0);  //enable TX 

  // Send Exit Sequence first
  if (sendExitSeqence) {
    JetiTransmitByte(0x7E, false);
    JetiTransmitByte(0x91, true);
    JetiTransmitByte(0x31, true);
  } else if (alarmCode != 0) {  // Send Alarm Code first, if alarmcode <> 0
    JetiTransmitByte(0x7E, false);
    JetiTransmitByte(0x92, true);
    JetiTransmitByte(0x23, true);
    JetiTransmitByte(alarmCode, true);
  }
  
  // 34 Byte Data Package
  if (line1[0] != 0) {
    JetiTransmitByte(0xFE, false);
    for (i=0; i<16; i++) JetiTransmitByte(line1[i], true);
    for (i=0; i<16; i++) JetiTransmitByte(line2[i], true);
    JetiTransmitByte(0xFF, false);    
  } else {
    // Exit Expander Test
    JetiTransmitByte(0xFE, false);
    for (i=0; i<32; i++) JetiTransmitByte(0, false);
    JetiTransmitByte(0xFF, false);    
  }
  UCSR0B &= ~(1<<TXEN0);  //disable TX
  UCSR0B |= (1<<RXEN0);  //enable RX, buffer is definetely empty after sending the frame
  
  return ack; // remember: last answer
}