AVR Freaks

The schematic there shows:

I would be astonished if the manufacturer doesn't supply this board with CKSEL fuses set to enable this 8MHz crystal (and CKDIV8 cleared) so have you really reprogrammed the fuses to revert to 1MHz?

What baud rate are you running at? 

For solid reliable serial comms, it is best to use an external xtal as the internal RC will drift with temperature and VCC voltage!

Jim

hosseinfathbag wrote:

my transmission work good , my reciever by polling code no work . RCX0 bit in UCSR0A is 1 !!!!!!

Isn't it supposed to be one?

Is your internal oscillator too far off from 8MHz to get good reception?

Post complete small test program, that shows your register setup.

How can you tell that

RCX0 bit in UCSR0A is 1 !!

Read UCSR0A and see if DOR or FE or UPE are set.

Tell configuration at both ends.  Mis-matched stop bit count, so framing errors?

Why would you have a "blocking" USART rx function in an ISR? 

Your design is questionable at best......

Jim

complete small code :

#define  F_CPU 12000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>


void UART_transmit_char (char data)
{
	while (!( UCSR0A & (1<<UDRE0)));                // wait while register is free
	UDR0 = data;                                   // load data in the register
}


char UART_recieve (void)
{
	while ( !(UCSR0A & (1<<RXC0)) );                 // wait while data is being received
	return UDR0;                                   // return 8-bit data
}
	
	
int main(void)
{
     
     DDRB |= (1<<DDB0); //SET OUT PUT
    
	//setting external interrupt 1 for BLT connection
	DDRD &= ~(1<<DDD3); //SET INPUT
	EICRA |= (1<<ISC10);  //Any logical change on INT1 generates an interrupt reques
	EIMSK |= (1<<INT1);  //Enable interrupt 1
	
	
    //setting uart 
    UBRR0H = (((F_CPU)/(9600*16UL)-1)>>8);                    // shift the register right by 8 bits for UBRRH
	UBRR0L = ((F_CPU)/(9600*16UL)-1);                        // set baud rate value for UBRRL      
            
	UCSR0B|= (1<<TXEN0)|(1<<RXEN0);                // enable receiver and transmitter
	UCSR0C|= (1<<UCSZ00)|(1<<UCSZ01);             // 8bit data format

    sei();
    while (1) 
    {

		
    }
}


ISR(INT1_vect){
	

    char character = 0;
	int menu = 0;
	
	
	character = UART_recieve(); // NOT WORK !!!!! RXC0 IS 1 !!!!!
	
	if( character == 'a') PORTB |= (1<<PORTB0);
}

OK, very tanx.

so, i want to use UART Receive interrupt , but in interrupt vector in atmega328 UART RX INT is lower than EXT INT1.

How can i use them ?

for example :

#define  F_CPU 12000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

#define BAUD 9600

char usart_recieve_char(void){

	char c = 0;
	while( udr==NULL);
	c = udr;
	udr = NULL;
	return c;
}

int main(){

    //init uart
    UBRR0H = (((F_CPU)/(BAUD*16UL)-1)>>8);                    // shift the register right by 8 bits for UBRRH
	UBRR0L = ((F_CPU)/(BAUD*16UL)-1);                        // set baud rate value for UBRRL      

	UCSR0B|= (1<<TXEN0)|(1<<RXEN0)|(1<<RXCIE0);                // enable receiver and transmitter
	UCSR0C|= (1<<UCSZ00)|(1<<UCSZ01);             // 8bit data format

    //init external interrrupt 1
    EICRA |= (1<<ISC10);  //Any logical change on INT1 generates an interrupt reques
	EIMSK |= (1<<INT1);  //Enable interrupt 1
	sei();

volatile char	udr = NULL;
volatile char usart_data[30];

    while(1){}
}

ISR(USART_RX_vect){

	static int i;
	udr = UDR0;
	usart_data[i++] = udr;

	if ( udr == 0X0D)  //  "\r"
	{

		for( int i =0;i<30;i++) usart_data[i] = NULL;
		i = 0;
	}

}

ISR(INT1_vect){

    char x = usart_recieve_char();  // not work ISR(UART_RX_vect) in this ISR
    if(x== "a") PORTB |= (1<<PORTB3);

}

are there?!

void UART_transmit_char (char data)
{
	while (!( UCSR0A & (1<<UDRE0)));                // wait while register is free
	UDR0 = data;                                   // load data in the register
}


char UART_recieve (void)
{
	while ( !(UCSR0A & (1<<RXC0)) );                 // wait while data is being received
	return UDR0;                                   // return 8-bit data
}

yes ,i know . in this project i connected bluetooth module INT to EXT INT1 in avr and i would like get data from bluetooth by UART RX interrupt in EXT INT1.

Your UART_receive() is blocking. Once you call it, the program will sit there in a  loop, waiting for the  character to arrive. During that time, nothing else can happen except interrupts.

Your earlier statement:

so, i want to use UART Receive interrupt , but in interrupt vector in atmega328 UART RX INT is lower than EXT INT1.

indicates that you are missing an important fact about AVR interrupts. The  order of the interrupt table is ONLY important if two should hit at EXACTLY the same instant. When that happens, the service routine that is higher on the list gets executed first. When that is finished, the next one is executed. Generally, UART receive interrupts do not need to be serviced instantaneously. You have until the  completion of the next character to get the first character read. If you  wait longer than this, you will loose the first character and the Data OverRun bit in UCSR0A (M328 family) is set. This is rarely a problem unless the baud rate is really high or unless you have another ISR that takes way too long to  execute.

Jim

Fuse no different at 12MHz compared 8MHz or 16MHz.

Jim

I am not sure how you reach that conclusion.

Jim

There is no reason to make trash = 0. You are just putting UDR0 character into the variable trash, over and over. There is no buffer, in the usual sense. The usual way would be to use an array as the buffer. If you insist on calling it trash, I would

for(int i=0;i<10;i++) 
    {
    trash[i] = UDR0;
    }

But even that is bad, because you are doing this over and over for each character. Not Good!

I recommend that you search out something like: buffered UART read

This is a very standard problem and there are examples all over the net.

Jim

But, he will get a separate interrupt on every character, no? And, I do NOT understand the insistence for using INT1 interrupt rather than a proper Rx Complete interrupt. The only thing that I can imagine is that the 200ms delay inside the ISR (really bad form) is long enough so that all of the characters will be received. But, the process in the code will ONLY identify the last one which is the last character to be copied into "trash".

I would do it something like this:

...
volatile uint8_t i;
volatile char * Buffer[10];
volatile uin8_t RxFlag;

ISR(USART_RX_vect)
    {
    char temp = UDR0;
    buffer[i] = temp;
    if (temp == '\r')  //carriage return at end of string?
        {
        i = 0;      //resetfor next message
        RxFlag = 1; //signal that a full message has arrived
        }
    else            //no carriage return yet
        {
        i ++;       //index for next character
        RxFlag = 0  //make sure the full message signal is clear
        }
    }

 Note that there is no protection against over-run of buffer[] or a few other nice details.

Jim