Arduino/ATMEGA_SERIAL_USB/ATMEGA_SERIAL_USB.ino

 /*
Title:		SerialCom.c 
Date Created:   6/9/2009
Last Modified:  6/9/2009
Target:		Atmel ATmega168
Environment:	AVR-GCC 
  
  Note: the makefile is expecting a '168 with a 16 MHz crystal.
  
Adapted from the Arduino sketch "Serial Call and Response," by Tom Igoe.
   
  //  This program sends an ASCII A (byte of value 65) on startup
  //  and repeats that until it gets some data in.
  //  Then it waits for a byte in the serial port, and 
  //  sends three (faked) sensor values whenever it gets a byte in.
   
   
   
Written by Windell Oskay, http://www.evilmadscientist.com/

Copyright 2009 Windell H. Oskay
Distributed under the terms of the GNU General Public License, please see below.

Additional license terms may be available; please contact us for more information.



More information about this project is at 
http://www.evilmadscientist.com/article.php/peggy



-------------------------------------------------
USAGE: How to compile and install



A makefile is provided to compile and install this program using AVR-GCC and avrdude.

To use it, follow these steps:
1. Update the header of the makefile as needed to reflect the type of AVR programmer that you use.
2. Open a terminal window and move into the directory with this file and the makefile.  
3. At the terminal enter
		make clean   <return>
		make all     <return>
		make program <return>
4. Make sure that avrdude does not report any errors.  If all goes well, the last few lines output by avrdude
should look something like this:

avrdude: verifying ...
avrdude: XXXX bytes of flash verified

avrdude: safemode: lfuse reads as E2
avrdude: safemode: hfuse reads as D9
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK

avrdude done.  Thank you.


If you a different programming environment, make sure that you copy over 
the fuse settings from the makefile.


-------------------------------------------------

This code should be relatively straightforward, so not much documentation is provided.  If you'd like to ask 
questions, suggest improvements, or report success, please use the evilmadscientist forum:
http://www.evilmadscientist.com/forum/

-------------------------------------------------
 

 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 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA


*/ 
#include <avr/io.h> 
#define F_CPU 16000000	// 16 MHz oscillator.
#define BaudRate 9600
#define MYUBRR (F_CPU / 16 / BaudRate ) - 1 

void delayLong() {
	unsigned int delayvar;
	delayvar = 0; 
	while (delayvar <=  65500U) { 
		asm("nop");  
		delayvar++;
	} 
}


unsigned char serialCheckRxComplete(void)
{
	return( UCSR0A & _BV(RXC0)) ;		// nonzero if serial data is available to read.
}

unsigned char serialCheckTxReady(void)
{
	return( UCSR0A & _BV(UDRE0) ) ;		// nonzero if transmit register is ready to receive new data.
}

unsigned char serialRead(void)
{
	while (serialCheckRxComplete() == 0)		// While data is NOT available to read
	{;;} 
	return UDR0;
}

void serialWrite(unsigned char DataOut)
{
	while (serialCheckTxReady() == 0)		// while NOT ready to transmit 
	{;;} 
	UDR0 = DataOut;
}



void establishContact() {
	while (serialCheckRxComplete() == 0) { 
		serialWrite('A');
	//	serialWrite(65U);
		delayLong();
		delayLong();
		delayLong();
		delayLong();
		delayLong();
		delayLong();
		delayLong();
	}
}

  

int main (void)
{ 
	
//Interrupts are not needed in this program. You can optionally disable interrupts.	
//asm("cli");		// DISABLE global interrupts.

		
	DDRD = _BV(1);
	DDRB = _BV(0) | _BV(1) | _BV(3) | _BV(5);
	 
	//Serial Initialization
	
 	/*Set baud rate */ 
	UBRR0H = (unsigned char)(MYUBRR>>8); 
	UBRR0L = (unsigned char) MYUBRR; 
	/* Enable receiver and transmitter   */
	UCSR0B = (1<<RXEN0)|(1<<TXEN0); 
	/* Frame format: 8data, No parity, 1stop bit */ 
	UCSR0C = (3<<UCSZ00);  
	
	 
	int firstSensor = 0;    // first analog sensor
	int secondSensor = 0;   // second analog sensor
	int thirdSensor = 0;    // digital sensor
	int inByte = 0;         // incoming serial byte
	
	
	PORTB |= _BV(1); // Turn on LED @ PB1
	

establishContact();  // send a byte to establish contact until Processing responds 

		PORTB &= 253U; // Turn off LED
	

for (;;)  // main loop										
{

	
	if (serialCheckRxComplete()) {
		PORTB |= _BV(1); // Turn on LED @ PB1
		
		inByte = serialRead();
		
		// Simulated data!
		firstSensor++;
		
		secondSensor = firstSensor * firstSensor;
		
		thirdSensor = firstSensor + secondSensor;
		
		serialWrite(firstSensor & 255U);
		serialWrite(secondSensor & 255U);
		serialWrite(thirdSensor & 255U);

		PORTB &= 253U; // Turn off LED
              
	}	

  }	//End main loop.
	return 0;
}