Serial port error statistics - any comparable data?

[Dan Stromberg]

On Sat, 29 Mar 2008 13:14:46 +0200, Hendrik van Rooyen wrote:

> Hi,
> 
> I have been doing some tests on a device that we are thinking of
> incorporating into a product, and I have seen that reception on a serial
> port at 115200 baud over about six metres of RS-232 cable makes
> mistakes, to the order of 125 lines with errors in them out of
> approximately 18.4 million lines of 65 or so chars - about one errored
> line in 147000, or one error character in 95 million.
> 
> The PC that is making the errors is a 64 bit dual core AMD machine
> running at 2 Gig, and I am running stock standard Open Suse 10.3 with
> the supplied Python 2.5.
> 
> What kind of bothers me is the nature of the errors - I seem to get only
> missing characters, as if an interrupt was missed.  There are no munged
> characters as one would expect if the errors were bit related.
> 
> Has anyone else seen anything like this, and am I worrying needlessly?
> 
> I realise that my production protocols will easily handle this almost
> non existent level of error - but if this were in microcontroller code
> that I had written myself, I would suspect that I was spending too long
> in some critical section of code.
> 
> - Hendrik

Have you verified that you have flow control enabled?

ISTR hearing there is one kind of software flow control and two kinds of 
hardware flow control.

I'm not serial expert, but ISTR that if your cable supports it, you 
should use RTS/CTS hardware flow control, and if it doesn't, use software 
flow control.