Serial port error statistics - any comparable data?

castironpi at gmail.com castironpi at gmail.com
Sun Mar 30 07:43:05 CEST 2008


On Mar 29, 4:26 pm, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
> Hendrik van Rooyen schrieb:
>
>
>
>
>
> > 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.
>
> RS232 is unfortunately as bad as a "protocol" as it can get. I've used
> it for communication with a microcontroller for just a few bytes every
> second. And it failed miserably, so I needed to implement a protocol on
> top of it.
>
> The machine spec is totally irrelevant - what is interesting is the
> serial hardware you use. Are you by any chance using a
> serial2usb-converter? I had nothing but troubles with these.
>
> if you have the chance, try & attach a machine with legacy rs232 port,
> and see if the errors still remain.

Transmit observed minus expected to cluster.  What kind of tables does
the input device build?



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