text: /*
   * The MIT License (MIT)
   *
   * Copyright (c) 2016 Nels D. "Chip" Pearson (aka CmdrZin)
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   *
   * Slave_A1B3.c
   *
   * Created: 1/31/2016 8:11:07 PM
   *  Author: Chip
   *
   * Demo code for Slave_A1B3 project.
   * Target: ATmega88A (by sure to set Project > Properties > Device to this AVR chip)
   * NOTE: Uncheck the CKDIV8 fuse to use an 8 MHz CPU clock.
   *
   * This code demonstrates a simple I2C Slave receiving a command and sending back data.
   *
   * The Commands from the Master are either:
   * SDA_W 55				- Prepare data to be read
   * SDA_R Data0 Data1	- Return 55 COUNT
   * NOTE: If a 0x55 is not the command byte, then 0 is returned instead of COUNT.
   */ 
  
  #include <avr/io.h>
  #include <avr/interrupt.h>
  
  #include "twiSlave.h"
  
  #define SLAVE_ADRS	0x40
  
  int main(void)
  {
  	uint8_t data;
  	uint8_t count;
  
  	count = 0;
  
  	twiSlaveInit( SLAVE_ADRS );		// Initialize TWI hardware for Slave operation.
  	
  	sei();							// Enable interrupts.
  	
  	twiSlaveEnable();				// Enable the TWI interface to receive data.
  	
      while(1)
      {
  		if( twiDataInReceiveBuffer() )
  		{
  			data = twiReceiveByte();
  
  			// If the data is 0x55, then prepare count to be returned, else have 0 returned.
  			if( data == 0x55)
  			{
  				twiTransmitByte( data );	// stuff command into TxBuf[]
  				twiTransmitByte( count );	// stuff count into TxBuf[]
  			}
  			else
  			{
  				twiTransmitByte( data );	// stuff command into TxBuf[]
  				twiTransmitByte( 0 );		// stuff 0 into TxBuf[]
  			}
  			// NOTE: The Master is expected to read both bytes before sending another command.
  			
  			++count;						// inc to track how many commands have been received.
  		}
      }
  }
  