[yocto] FW: [meta-freescale] serial port timeout before expected # of bytes arrives

[Jeff Osier-Mixon]

Hi Thanassis - if there is no reply here, you might try joining and
posting on the meta-freescale mailing list
(https://lists.yoctoproject.org/listinfo/meta-freescale)

On Thu, Jul 4, 2013 at 7:24 AM, Thanassis Silis <djnass_18 at hotmail.com> wrote:
>
>
> ________________________________
> From: djnass_18 at hotmail.com
> To: meta-freescale at yoctoproject.org
> Date: Thu, 4 Jul 2013 13:40:10 +0000
> Subject: [meta-freescale] serial port timeout before expected # of bytes
> arrives
>
> Hello everyone,
> I am trying to port an application that is receiving/sending data through
> the serial port.
> On the sabrelite board that is the /dev/ttymxc0 port, ie the 2ndary serial
> port (the primary being /dev/ttymxc1).
>
> I am using the functions select() and read() to read from the serial port ,
> in order to implement a timeout mechanism that is waiting for a few seconds
> for bytes to arrive and if should they not arrive, then the timeout is
> reached.
>
> The receiving loop works like this:
>
> I wait for 2 bytes - the opcode of the command.
> Once I resolve a code, I wait for 4 bytes designating the length of data
> that will follow (depending on the command)
> I create a buffer in my application of size equal to the length I received
> above.
> I start receiving the data.
>
>
>
> Note that I have implemented reception of the data in 2 ways (since the 1st
> way used to work, it was tried as is. Then, I tried the next as well):
>
>
>
> a)receive my data using a for loop, reading() one byte at time. until all
> the expected bytes arrive , or a timeout is reached.
>
> b)receive my data using a while loop where I ask for all the remaining bytes
> to be read(). Read() returns how many bytes have actually arrived, so I
> update the remaining Bytes and re-read(). Again if a select() times-out
> without any data arriving, the loop will exit.
>
>
> Now, my problem is that while applications seem to be using this port
> without any problem (f.e. minicom, rx, cat /dev/ttymxc0, echo "something" >
> /dev/ttymxc0 ) , through the application I get timeouts for any file that is
> bigger than 3-4kBytes.
>
>
> Say I am trying to send a file 138kB. I may fail at byte ~40k, ~56k, or even
> ~12k. This is very weird. And I don't know what to assume is going wrong.
> Slow processing on the local end seems to not be a problem, as I can read
> (in (b) above) approx 58 bytes in the beginning and then 1 byte at a time.
> Could it be the memory buffer? If yes, how can I increase its size? Could
> another application be interfering with /dev/ttymxc0?
>
>
>
> I am running fsl-image-test with all -dev, -sdk & -dbg options enabled.
>
>
> Thank you for your help.
>
>
>
>
>
>
>
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-- 
Jeff Osier-Mixon http://jefro.net/blog
Yocto Project Community Manager @Intel http://yoctoproject.org