Programming Problems Write C code to setup the AVR USART peripheral for communic

Question

Programming Problems Write C code to setup the AVR USART peripheral for communication using the following configuration and then send the character A' once. The AVR has an 8MHz system clock. Write only the code needed to configure the peripheral and send the character, do not write an entire C program. 1. i. ii. iii. iv. v. vi. Asynchronous communication 8 bit characters Receiver and transmitter enabled Odd parity Normal communication speed Baud rate of 19,200 bits per second vii. 2 stop bits (10 Points)

Explanation / Answer

#include <avr/io.h>

#include <util/delay.h>

#ifndef F_CPU

#define F_CPU 8000000

#endif

//set desired baud rate

#define BAUDRATE 1200

//calculate UBRR value

#define UBRRVAL ((F_CPU/(BAUDRATE*16UL))-1)

//define receive parameters

#define SYNC 0XAA// synchro signal

#define RADDR 0x44

#define LEDON 0x11//switch led on command

#define LEDOFF 0x22//switch led off command

void USART_Init(void)

{

//Set baud rate

UBRRL=(uint8_t)UBRRVAL; //low byte

UBRRH=(UBRRVAL>>8); //high byte

//Set data frame format: asynchronous mode,no parity, 1 stop bit, 8 bit size

UCSRC=(1<<URSEL)|(0<<UMSEL)|(0<<UPM1)|(0<<UPM0)|

(0<<USBS)|(0<<UCSZ2)|(1<<UCSZ1)|(1<<UCSZ0);

//Enable Transmitter and Receiver and Interrupt on receive complete

UCSRB=(1<<TXEN);

}

void USART_vSendByte(uint8_t u8Data)

{

// Wait if a byte is being transmitted

while((UCSRA&(1<<UDRE)) == 0);

// Transmit data

UDR = u8Data;  

}

void Send_Packet(uint8_t addr, uint8_t cmd)

{

USART_vSendByte(SYNC);//send synchro byte

USART_vSendByte(addr);//send receiver address

USART_vSendByte(cmd);//send increment command

USART_vSendByte((addr+cmd));//send checksum

}

void delayms(uint8_t t)//delay in ms

{

uint8_t i;

for(i=0;i<t;i++)

_delay_ms(1);

}

int main(void)

{

USART_Init();

while(1)

{//endless transmission

//send command to switch led ON

Send_Packet(RADDR, LEDON);

delayms(100);

//send command to switch led ON

Send_Packet(RADDR, LEDOFF);

delayms(100);

}

return 0;

}

#include <avr/io.h>

#include <avr/interrupt.h>

#include <util/delay.h>

#ifndef F_CPU

//define cpu clock speed if not defined

#define F_CPU 4000000

#endif

//set desired baud rate

#define BAUDRATE 1200

//calculate UBRR value

#define UBRRVAL ((F_CPU/(BAUDRATE*16UL))-1)

//define receive parameters

#define SYNC 0XAA// synchro signal

#define RADDR 0x44

#define LEDON 0x11//LED on command

#define LEDOFF 0x22//LED off command

void USART_Init(void)

{

//Set baud rate

UBRRL=(uint8_t)UBRRVAL; //low byte

UBRRH=(UBRRVAL>>8); //high byte

//Set data frame format: asynchronous mode,no parity, 1 stop bit, 8 bit size

UCSRC=(1<<URSEL)|(0<<UMSEL)|(0<<UPM1)|(0<<UPM0)|

(0<<USBS)|(0<<UCSZ2)|(1<<UCSZ1)|(1<<UCSZ0);

//Enable Transmitter and Receiver and Interrupt on receive complete

UCSRB=(1<<RXEN)|(1<<RXCIE);//|(1<<TXEN);

//enable global interrupts

}

uint8_t USART_vReceiveByte(void)

{

// Wait until a byte has been received

while((UCSRA&(1<<RXC)) == 0);

// Return received data

return UDR;

}

ISR(USART_RXC_vect)

{

//define variables

uint8_t raddress, data, chk;//transmitter address

//receive destination address

raddress=USART_vReceiveByte();

//receive data

data=USART_vReceiveByte();

//receive checksum

chk=USART_vReceiveByte();

//compare received checksum with calculated

if(chk==(raddress+data))//if match perform operations

{

//if transmitter address match

if(raddress==RADDR)

{

if(data==LEDON)

{

PORTC&=~(1<<0);//LED ON

}

else if(data==LEDOFF)

{

PORTC|=(1<<0);//LED OFF

}

else

{

PORTC|=(1<<0);//LED OFF

_delay_ms(10);

PORTC&=~(1<<0);//LED ON

}

}

}

}

void Main_Init(void)

{

PORTC|=(1<<0);

DDRC=0X001;

sei();

}

int main(void)

{

Main_Init();

USART_Init();

while(1)

{

}

return 0;

}

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