[Gllug] re: uart overrun problem
blue.dragon at blueyonder.co.uk
Thu Dec 4 08:31:54 UTC 2003
On Thu, 4 Dec 2003, t.clarke wrote:
> A search on the web reveals a setserial package at sourceforge whic has amongst
> other features a 'latency' feature (which is presumably controlled by the rx
> trigger level). You could try downloading, compiling, and using this.
> Setting a 'low latency' may then cure the problem.
> However, the question still remains as to why this is happening anyway:
> since uart overruns are simply due to the cpu not being able to clear the
> receive buffer on the uart fast enough, the possibilities would seem to be:
> a) running the serial line too fast
4800bps too fast?
> b) cpu too slow
Modern Processor too slow? Serial Lines have been in use for the last 30
years (think again)
> c) cpu overloaded with other non-interruptible load
As many pages on the internet "Caused by a multi-process"
> d) crap uart with too small a buffer (any decent mobo should be using a 16550
> or compatible uart)
You mean 16550A. The 16550 is crap its only got a 1 byte buffer.
> e) problems with the serial driver code ??
> f) shared interrupt not being handled efficiently ??
> I have a vague feeling that the driver reports on receiver buffer overruns
> - available by interrogating the appropriate /proc filesystem entry.
> A post containing details of your hardware/o-s config might be helpful to
> others to assist.
I'll have a look at sourceforge.
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