Sam,

What sort of clock are you running the PIC with?   And at what
frequency?
You may be getting out of sync with the PIC and the PC if the frequency
is
Off by more than a few percent.   Try lowering the baud rate on both the
PC
And your PIC board, and see if that makes any difference.  If it does,
you should
Look at your clocking scheme.   And as an FYI, on anything but maybe
2400 baud and
Lower, the internal RC clock is just not stable or accurate enough to
suffice for
Accurate baud rates.

Hope this helps.


	
Regards,

	
Jim

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of Przemyslaw Lopaciuk
Sent: Friday, January 12, 2007 2:43 PM
To: piclist@mit.edu
Subject: [EE] Very odd problem with RS232...

Hi,
I've encountered very odd thing with RS232 and I'm stuck... I don't have
any idea what can be the problem..
I want to read information from RS232 ... I use 9600 baud rate, hardware
and software handshaking.
The sequence looks like that...
 
1) DTR and RTS high. PC sends 0x80, Device sends 0x01 back
2) PC sends 0x81, Device sends 0x00 back.
3) PC sends 0x01 and then lowers DTR
4) PC sends 0x12, device sends 8 bytes back ( some information )
 
It works perfectly on PC but when I use my board it doesn't. When using
the board I can get through step 1 and step 2. I can't get the 8 bytes
from thep 4 though. When I test the board connecting it to PC the data
goes through correctly. 
 
I even thought that it might be voltage ( I've got 7,5 V on my board ),
so I put resistor on the cable and lowered the voltage to 7,5 V from PC
( it is 12 normally ). The PC can still get data from the Device.
 
I don't know where did I make the mistake. Maybe I don't know something
about RS232 standard?
 
Please help. 
 
Thank you in advance.
 
Sam
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