Rogue symbols on hyperterminal

[chylok]

Hi all,
I'm getting a weird problem when using a null modem cable to connect two PCs together, using Hyperterminal. I'm doing this to test RS232 ports (used a loopback without any issues). Once I've made the connection (both ways) I am getting symbols for every second character. This only happens when I keep a key held down, it happens with any key. I've checked the settings in hyperterminal both ends are setup the same, also it is only happening in one direction. The machine recieving the symbols has a configurable 4 port RS232 card. I am convinced it is something to do with this.
I have connected two ports on the card together, no symbols. Any external rs232 connection causes the symbols.
I know this is a long shot but has anyone got a clue what this could be?

Cheers,
Chylok

 

[edfair]

What type of serial chip is involved? Less than 16550 have small buffers that cause buffer overruns.
If you are holding the key down you may be getting more than 2 characters, and that would definitely point to a buffer problem.
You could try slowing the transmission rates to below 9600 baud, that being the top rate at which communications can reliably work with the overhead that windows puts on systems.



Ed Fair
Give the wrong symptoms, get the wrong solutions.