I would sugest to first test the comunications without the handshaking.
Transmmit a few secuence of bytes and see if everything is allright. You'll
spot the problem easily. If that test goes fine, you most propably have an
error in your handshaking code.

Regards,

Mauricio Jancic
Janso Desarrollos
www.janso.com.ar
info@janso.com.ar
(54) 11-4502-2983
 

> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of Przemyslaw Lopaciuk
> Sent: Friday, January 12, 2007 5:43 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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