# USART Issues

#### Billt321

##### New Member
Hi,

Recently i have been trying to get interrupt driven serial working for a project of mine, however i have been struggling to get it to work. I am using an Atmega328p (16Mhz external xtal), and an FTDI231x to communicate to a PC . I believe all the hardware works fine, as using Arduino IDE i can get the serial to work, but i need to use it in Atmel Studio 6. The transmit sort of works, i can see the Tx LED flashing, however i only see zeros or symbols with Realterm. The data sent by the AVR looks to be wrong on a scope aswell. Also, when sending data to the AVR, the Rx interrupt doesn't fire either. I have also tried a lot of example code of the web, checking to ensure that the Fcpu values and such were correct, and none have worked. I have also disabled ckdiv8 in the fuses. Any suggestions?

Thanks in advance, Bill.

Code:
#include <avr/io.h>
#include <util/delay.h>

#define F_CPU 16000000UL
#define FOSC 16000000
#define BAUD 9600
#define MYUBRR (FOSC/16/BAUD)-1

volatile char usartReceive;
volatile int rxF;
unsigned char buffer;

void USART_init();

sei();

int main(){
//Setup
USART_init();

while ( !( UCSR0A & (1<<UDRE0)) ) // Wait until buffer is empty
buffer = "Hello";
UDR0 = buffer;

//Main Loop
while(1){
while ( !( UCSR0A & (1<<UDRE0)) )
UDR0 = 0b01010101
_delay_ms(1000);
if(rxF == 1){
while ( !( UCSR0A & (1<<UDRE0)) )
UDR0 = usartReceive;
rxF = 0;
}
}
}

void USART_init(){

UBRR0H = (unsigned long)(MYUBRR>>8);
UBRR0L = (unsigned long)(MYUBRR);
UCSR0B |= (1<<RXEN0)|(1<<TXEN0)|(1<<RXCIE0);
UCSR0C |= (1<<UCSZ01)|(1<<UCSZ00);    // 8 Data bits, one stop bit

}
ISR (USART_RX_vect){

usartReceive = UDR0;
rxF = 1;

}

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