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Re: [ts-7000] ttyS0 linux serial buffer size

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Subject: Re: [ts-7000] ttyS0 linux serial buffer size
From: "Don W. Carr" <>
Date: Tue, 19 Dec 2006 16:34:59 -0600
On a serial port there is no such thing as end of file. I have always assumed that a return value of 0 is because there was a timeout. A value of -1 would indicate an error. Of course if you have not set a timeout, you should wait for ever, and the only valid return values would be -1 and 1 or greater. You should never see a zero. Let me know if I am interpreting this wrong. Don.

On 12/19/06, Jim Jackson <> wrote:



On Tue, 19 Dec 2006, kendwyer wrote:

> Hi,
>
> I am using the TS-7260 system for my application. I have found that
> the tty (at least ttyS0) will only read 4096 bytes as a defualt
> maximum, when my user code executes the following, r =
> read(ft,ser_databuf,4096);.
>
> When I change the code as follows:
>
> res1 = read(ft,ser_databuf,8192);
>
> I still only read 4096 bytes...
>
> How/where do I change the code to read greater than 4096?
>

Read the man page for the read function

man 2 read

on most any linux desktop.

I quote......

On success, the number of bytes read is returned (zero
indicates end of file), and the file position is advanced
by this number. It is not an error if this number is
smaller than the number of bytes requested; this may hapÂ
pen for example because fewer bytes are actually available
right now (maybe because we were close to end-of-file, or
because we are reading from a pipe, or from a terminal),
or because read() was interrupted by a signal.

re-code your application to loop on the read call until you've read all
the bytes.




--
Dr. Don W. Carr
J. G. Montenegro 2258
Guadalajara, Mexico
+52-333-630-0704
+52-333-836-4500 ext 2930 __._,_.___


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