Reading from /dev/ttyUSB0
Anton Komarov
trying to read data from /dev/ttyUSB0 device
with command cat < /dev/ttyUSB0
according to strace i see that data flow comes in several parts,
althoung on i386 box data comes in one part
it looks like this
read(0, "G", 32768) = 1
write(1, "G", 1G) = 1
read(0, "LG,0462.15", 32768) = 10
write(1, "LG,0462.15", 10LG,0462.15) = 10
read(0, "00,NFM,", 32768) = 7
write(1, "00,NFM,", 700,NFM,) = 7
read(0, "0,0,WORK ROAD", 32768) = 13
write(1, "0,0,WORK ROAD", 130,0,WORK ROAD) = 13
read(0, ",ROAD P, M-8 ", 32768) = 13
write(1, ",ROAD P, M-8 ", 13,ROAD P, M-8 ) = 13
read(0, "ENT,1,0,77,", 32768) = 11
write(1, "ENT,1,0,77,", 11ENT,1,0,77,) = 11
read(0, "NONE,NONE\r", 32768) = 10
) = 10E\r", 10NONE,NONE
so the main question is aren't there any bugs in
kernel/driver/hardware anything else what is connected to BBxM that
enables flow segmentation?
using 3.0.17 kernel from Angstrom and pl2303 driver for usb-serial interaction
Joshua Lamorie
On Mar 12, 2012 9:31 AM, "Anton Komarov" <anton....@gmail.com> wrote:
>
> so the main question is aren't there any bugs in
> kernel/driver/hardware anything else what is connected to BBxM that
> enables flow segmentation?
>
What do you mean by 'flow segmentation'? Are you familiar with termios and programming for Linux serial ports?
Joshua
Anton Komarov
when i am talking about flow segmentation i mean several lines coming
from serial port not one,
as it appears in i386 system. Moreover if i am polling serial
interface with 50 ms interval there are errors from the device.
When i do the same polling on i386 box there are no errors ever.
How to perform deep debug to see what happens with flow of commands
and answers?
It seems to me there must be cache issue or smth like that.
On Mar 13, 2:50 am, Joshua Lamorie <joshua.lamo...@gmail.com> wrote:
Joshua Lamorie
I'm sorry to be pedantic, but I think you need to provide much more details about what you are doing.
On Mar 13, 2012 5:17 AM, "Anton Komarov" <anton....@gmail.com> wrote:
>
> Sure i do,
Sure you do, what?
>
> when i am talking about flow segmentation i mean several lines coming
> from serial port not one,
> as it appears in i386 system.
This sounds like you don't have the correct termios settings if you want to receive reads of data separated by line endings. You could also try fgets.
Moreover if i am polling serial
> interface with 50 ms interval there are errors from the device.
> When i do the same polling on i386 box there are no errors ever.
>
What errors are you seeing? What do you mean by polling? Is this non blocking? What speed are you running the serial connection at?
> How to perform deep debug to see what happens with flow of commands
> and answers?
Deep, like within the kernel?
> It seems to me there must be cache issue or smth like that.
>
Serial port programming in Linux is non-trivial and there are many, many annoying little behaviours with the various termios settings.
Are you sure this is a problem with the beagle[board/bone]? You said this was a USB serial dongle.
This might not be the best forum for this discussion.
Joshua
Anton Komarov
as a read/write software i am using 'echo' and 'cat' utils
terminal is configured with stty
so taking the same config of terminal and doing echo in cycle and
reading with cat i am getting pretty different behaviour. Dongle is
not changed in this experiments.
So e.g.
stty -F /dev/ttyUSB0 115200
while (true); do echo -ne 'GLG\r' > /dev/ttyUSB0; sleep 0.05; done
cat < /dev/ttyUSB0 (other shell)
in i386 box i am getting
lines with correct information w/o any errors
line by line
when i am running the same code on bbxm
i am getting segmented lines
and device which i am polling (this i mean writing and reading in
cycle) reports me error code as it would get wrong command.
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