AVR Freaks

typical code here..
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http://svn.savannah.gnu.org/viewvc/avr-libc/trunk/avr-libc/libc/misc/eewr_word.S?revision=1979&view=markup

This requires some knowledge of the avr-gcc ABI but basically the first parm (addr) will be in R25:R24 the the second parm (16 bit value to write) will be in R23:R22. The first call will write R22 (low byte) then second writes R23 (high) but what I don't see is the EEAR increment but the must be implied by the write_r18 routine. The whole of avr-gcc does things little endian. I doubt the EEPROM routines would be any different.
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Hope you are having a good day by the way ;-)

 

Teh Datasheet provides plenty of information on this.  The one I use is 11.052Mhz, as it gives 0% error.

 

That can be your crystal frequency, or your code, or both.

 

Have you programmed the fuses in the AVR for an external crystal?  I am thinking yes, but I have nothing to confirm this.

 

I am not at my PC today with time to write code, but I would suggest you write a simple loopback program that does the following(based on a 16MHz crystal)

 

USART RX ISR
{
    uint8_t data;  //local variable
    data = UDR0;  //get teh data from UDR0
    UDR0 = data;  //send the received data back to the terminal
}

void main(void)
{
    //init the usart
    Configure the USART for 8-N-1
    Set Baud to 57600 - you will need the x2 enabled for this
    Enable the RX interrupt
    Enable the RX and TX

    sei();

    while(1)
    {
        //hang out here and do nothing until data comes in
    }
}

57600 is the fastest the USART can go within error specs for a 16MHz crystal.  If everything is in order, anything you type on the terminal should be echoed back to it.

 

 

JIm

 

EDIT:

Heres the config:

void main(void)
{
    // USART initialization
// Communication Parameters: 8 Data, 1 Stop, No Parity
// USART Receiver: On
// USART Transmitter: On
// USART Mode: Asynchronous
// USART Baud Rate: 57600 (Double Speed Mode)
UCSRA=(0<<RXC) | (0<<TXC) | (0<<UDRE) | (0<<FE) | (0<<DOR) | (0<<UPE) | (1<<U2X) | (0<<MPCM);
UCSRB=(1<<RXCIE) | (0<<TXCIE) | (0<<UDRIE) | (1<<RXEN) | (1<<TXEN) | (0<<UCSZ2) | (0<<RXB8) | (0<<TXB8);
UCSRC=(1<<URSEL) | (0<<UMSEL) | (0<<UPM1) | (0<<UPM0) | (0<<USBS) | (1<<UCSZ1) | (1<<UCSZ0) | (0<<UCPOL);
UBRRH=0x00;
UBRRL=0x22;

sei();

   while(1)
   {
       //do nothing and wait
   }
}

 

 

Yup, thats the proper setting for external crystal.

 

JIm

 

Fuses have nothing to do with it.  And how do you know that the Interrupt fired when you send data?  The TX and RX pins are separate entities.  Unless your terminal program is sending data at the same time they do not interact with one another.

 

JIm

What crystal is this number for?

 

JIm

As written - because you are repeatedly setting all bis of LED_PORT back to 0 in the while(1) then even if RXC fires it should only be momentary but will then be turned off almost immediately anyway. However this is what the mega16 datasheet says about the RXC interrupt flag:

 

So your code needs to be:

ISR(USART_RXC_vect) {
    uint8_t dummy;
    LED_PORT |= (1<<LED_PIN0);  
    dummy = UDR;
}

so the read of UDR clears the RXC flag. Otherwise as soon as one interrupt condition occurs it will never clear and the ISR() will simply run over and over again.

Darien,

Try this:

/*
 * Mega16 USART.c
 *
 * Created: 4/1/2019 12:18:14 PM
 * Author : jgmDESIGNS
 */ 

#define F_CPU 16000000ul
#include <avr/io.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <string.h>
#include <avr/pgmspace.h>
#include <avr/eeprom.h>


ISR (USART_RXC_vect )
{
	uint8_t data;
	data = UDR;
	UDR = data;
}

void avr_init(void)
{
	// USART0 initialization
	// Communication Parameters: 8 Data, 1 Stop, No Parity
	// USART0 Receiver: On
	// USART0 Transmitter: On
	// USART0 Mode: Asynchronous
	// USART0 Baud Rate: 57600 (Double Speed Mode)
	UCSRA=(0<<RXC) | (0<<TXC) | (0<<UDRE) | (0<<FE) | (0<<DOR) | (0<<PE) | (1<<U2X) | (0<<MPCM);
	UCSRB=(1<<RXCIE) | (0<<TXCIE) | (0<<UDRIE) | (1<<RXEN) | (1<<TXEN) | (0<<UCSZ2) | (0<<RXB8) | (0<<TXB8);
	UCSRC=(1<<URSEL) | (0<<UMSEL) | (0<<UPM1) | (0<<UPM0) | (0<<USBS) | (1<<UCSZ1) | (1<<UCSZ0) | (0<<UCPOL);
	UBRRL=0x22;
}

int main(void)
{
	
	avr_init();
	
	sei();
		
	
    /* Replace with your application code */
    while (1) 
    {
		//just hang out here.  THe interrupt does the work
		
    }
}

Use a 16MHz crystal.  Baud rate is set for 57600.  In your terminal whatever you type will be echoed back.

 

Forget about your LED's etc as we have no idea how your custom board works.  Get the AVR to talk to your terminal program.  THEN we can move on.

 

JIm