Serial I/O

Implemented in C, this program is designed to  repeatedly transmits the characters of a string through the built-in USART port on the AVR Xplained mini 328 board. It begins by defining the CPU clock frequency and the Baud rate by calculating the necessary register for accurate timing. Using the USART hardware of the AVR, the registers are initialized, enabling the receiver and transmitter to set up the 8-bit data format. The other function ‘Transmit()’ handles the transmission of each character in the string correctly. It sends each character of the string sequentially, waiting for the transmit buffer to empty before sending the next character. The program runs in an infinite loop since there is no final break statement{until power is lost). In the main loop, the program iterates through every character in the string, sending over each letter to the transmit function. There is a 500ms delay between each transmission. 

#define F_CPU 16000000UL // 16MHz clock from the debug processor

#define BAUD 9600 // set the baud rate to 9600

#define BAUDRATE ((F_CPU/(16UL*BAUD)) - 1) // calculate the baudrate

#include <avr/io.h> // library to be able to use the functions

#include <util/delay.h> // time delay library

#include <string.h> // include string library

void initialize() {

// clear the high bits because they are not needed for this lab. Don't need that many bits

UBRR0H = (BAUDRATE>>8);

UBRR0L = BAUDRATE; // set the Low byte register to the BAUDRATE

UCSR0B |= (1<<TXEN0 ) ; // enable the transmitter

UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01); // set to 8 bit data format

// don't need to set the stop bit since it is 1 by default

}

void Transmit(char strChar) {

while ( !( UCSR0A & (1<<5) ) ) {} // Wait for empty transmit buffer (isolates the 5th bit)

UDR0 = strChar;

}

int main(void) {

char userString[] = "827695876\r\n"; // string for the RedID characters

int strSize = sizeof(userString); // get the size of the string

initialize()

while(1){

for (int i = 0; i < strSize; i++) {

Transmit(userString[i]);

}

_delay_ms(500); // 500ms delay

}

}