Serial Port Returning Garbage. Why?

[bowman]

max wrote:
>
> No, I'm not. It's just Transmit, Receive, and Ground. Our device
> doesn't use any of the other signals, and the implementation doesn't
> use QON/QOFF. Would it make a significant difference if I do?

It might, if the slave end is a relatively slow device. For instance, the 
older SBC UARTs or microcontroller internal UARTs might not be able to keep 
up with the transmission, particularly if they have to do something with 
each byte as it is received. Usually the receiver will use a DTR signal to 
indicate it is busy, and the sender won't start the next byte until the 
receiver is ready. I'm assuming by 3 wires, you mean RX, TX and GND, so 
even if the hardware handshake is being attempted, it won't be seen across 
the cable.

It is hard to say without knowing your setup. It is possible when you test 
with HyperTerminal, you are typing the command in, so it really is sent 
very slowly, but in the working system the master sends the command string 
much faster and they are getting out of sync.

Or, it could just be that HyperTerm is setting the start/stop bits, parity, 
or something a little differently. I don't think it is the baud rate, since 
that usually results in all garbage characters.