Hi All.
Following is our setup ::
*
A pc-in-a-box embedded system, with 2 COM-ports, 2 USB-2.0 ports and 1
USB-3.0 port
*
Ubuntu 14.0.4.3 installed as the OS.
*
Vanilla C-application, reading/writing from 2 COM-ports and 1 USB-2.0 port.
First discussing about the USB-2.0 port, we have added a udev-rule, so
that the USB is always identified as "/dev/ttyUSB0".
In case the USB is not present, an appropriate error is returned via
the "open" call, and our binary exits (and restarts).
For the COM-ports, they are hard-linked to "/dev/ttyS0" and
"/dev/ttyS1" respectively.
Now, in an ideal scenario, all the 3 ports have the devices connected to them.
So, the
binary-start => open-ports => read/write => close-ports-before-binary-exit
cycle works fine.
However, if let's say no device is physically connected to
"/dev/ttyS0", then the above cycle works ONLY THE FIRST TIME of
device-start.
Thereafter, the app-binary simply hangs trying to open "/dev/ttyS0"
(with no error being returned from the "open" call).
I am using
open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_SYNC)
call for opening the port in question.
So is the code incorrect? Or this is expected behaviour? Or something
is wrong at kernel-level? Or something is wrong at the hardware-level?
Sorry for me being all over the place, but I am a serious newbie, with
loads of willingness to learn :)
So will be grateful for any pointers on how to identify the root-cause
and fixing it.
Thanks and Regards,
Ajay
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