Using XON/XOFF

Started by Sven Haedel July 17, 2003
Hello,

I programmed an application using the UART (interrupt driven) on a Mega8
with the STK500. Everything works fine, except I do not receive every
byte I send to the AVR. It reads and executes the commands I send to it,
but while executing, it misses some bytes. I tried to implement Xon/Xoff
Handshaking but after I send Xoff to the Computer, Xon is never sent.
Because I use every spare I/O, I cannot use rts/cts. Please help me and
tell me how to do Xon/Xoff handshaking.

Thanks for any help
Sven


Hi Sven,

Normally Xon/Xoff is used by the receiver to tell the transmitter to
slow down. In order to use it effectively, you need to have some type of
buffer.

When your receive buffer gets say 3/4 full, you send an XOFF which tells
the transmitter to stop sending characters. Of course you have to allow
for a few additional characters to arrive.

Then when the receive buffer gets down to say 1/4 full, the receiver
sends an XON which tells the transmitter to resume sending data.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/ > -----Original Message-----
> From: Sven Haedel [mailto:sven@sven...]
> Sent: Thursday, July 17, 2003 2:20 PM
> To: avrclub@avrc...
> Subject: [AVR club] Using XON/XOFF > Hello,
>
> I programmed an application using the UART (interrupt driven)
> on a Mega8 with the STK500. Everything works fine, except I
> do not receive every byte I send to the AVR. It reads and
> executes the commands I send to it, but while executing, it
> misses some bytes. I tried to implement Xon/Xoff Handshaking
> but after I send Xoff to the Computer, Xon is never sent.
> Because I use every spare I/O, I cannot use rts/cts. Please
> help me and tell me how to do Xon/Xoff handshaking.
>
> Thanks for any help
> Sven > ------------------------ Yahoo! Groups Sponsor
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Thank you.

I had my XON send limit set too low.
Now at it works fine.

Sven