Linux Programming Discussions

[Karl Wilbur]

What hardware are you using?

Karl Wilbur
karl at karlwilbur.net


On Tue, Aug 31, 2010 at 3:35 PM, Martin McCormick
<martin at x.it.okstate.edu>wrote:

>        I am writing some C code to manage the operation of a
> new scanner radio and it is mostly coming along well but I have
> run in to some odd behavior from a RS-232 port routine I stole
> from a Linux HowTo on serial communications.
>
>        One calls the routine and it stores characters in to a
> buffer or transmits data from a buffer. Receiving 50 or 60
> characters is a piece of cake. Everything works as expected but
> receiving a longer string such as 60 to 70 or more characters,
> the first read brings back some of the chars from the previous
> read even though the buffer was zero'd out. A second read gets
> all the character that should have been there in the first read.
>
>        Needless to say, this is not good but I discovered I can
> put a 1-second sleep before the next read and then it always
> gives the correct data.
>
>        When I get through, the radio will be totally accessible
> thanks to its serial control capabilities and to Linux, in this
> case, Vinux.
>
>        Are there any Linux discussion groups that would be
> really good for this question?
>
>        The receiver control program really creeps along with
> those forced 1-second pauses before every serial read.
> Interestingly enough, I wouldn't call it flaky because it does
> exactly the same wrong thing every time and it is always on a
> longer receive string. The buffer is set for 1024 characters and
> none of the reads have even come close to overflowing it so
> that's not the problem. Also, if the sleep is even slightly less
> than 1 full second, such as .75 seconds, I still get the bogus
> read.
>
>        Again, any ideas as to where to take this question are
> appreciated.
>
> Martin
>
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