Problem with using AVR UART to communicate with PC

[xinz]

I try to use AVR's uart to communicate with my pc but failed so far.
I wrote a code to echo a byte that sent from my pc (hyperterminal,etc) back.

when I sent a byte(char) from hyperterminal, my avr always sent 0x80 back (I tried sent a-z and 0-9)
except for this char: y,i,o,j,k,l,z,x,n,m,8,9. my avr don't sent anything back.

the code:

.INCLUDE "tn2313def.inc"
RJMP Main

Main:
ldi r16, RAMEND
out SPL, r16

clr r17
ldi r16, 51

out UBRRH, r17
out UBRRL, r16

ldi r16, 0b00000110
out UCSRC, r16

ldi r16, (1 << RXEN) | (1 << TXEN)
out UCSRB, r16

readbit:
sbis UCSRA, RXC
rjmp readbit
in r17, UDR

transbit:
sbis UCSRA,UDRE
rjmp transbit

out UDR,r17
rjmp readbit


I used 8MHz crystal, I set UBRR=51 for 9600 baud rate.
I also tried different baudrate, crystal, frame format, other Atiny2313, Atmega8 but the result is failed.
I also can't say my serial port is damaged since I can update my code using AVR910 through serial port.

any solution?

 

[bosparra]

Re: AVR UART problem

First place to start looking, would be the fuse bits. Make sure that fuses are set correctly for the type of crystal you are using.

 

[Tahmid]

AVR UART problem

Hi,
It seems fine,
Just at the end try:

readbit:
sbis UCSRA, RXC
rjmp readbit
in r17, UDR

transbit:
sbis UCSRA,UDRE
rjmp transbit

out UDR,r17

check2:
sbis UCSRA,TXC
rjmp check2

rjmp readbit

Hope it helps.
Tahmid.

 

[xinz]

Re: AVR UART problem

thanks.
it's a hardware problem (my dev.board).
when I test it on breadboard everything is ok