[uClinux-dev]problem of communicating between uClinux & uC/OS-II

[SIE]

2007/10/11, Stanislav Meduna <stano at meduna.org>:
>
> SIE wrote:
>
> > We have a project that will communicate with two different OS(uClinux
> > and uC/OS-II) through UART.
>
> What speed are you using,what receive FIFO size does the S3C4510B's
> UART have and what serial driver are you using? I can't read
> http://www.mculand.com/sub1/mcu/arm7tdmi_device/s3c4510.htm
> but if the source is correct, it seems that the FIFO is 32 bytes.


S3C4510B,a little different from the page you mentioned,does not have a fifo
for uart.



> However,uClinux is not a real-time OS,
>
> Well, even (hard) real-time only guarantees that you get
> the processing in a specified time, and not that the time
> is short enough to be able to handle the UART ;)


I got it,thanks.


With 32 byte and 115 kbps you need to service an interrupt
> in 2.6 ms, which should be more than enough. Is there
> any other hardware that might be blocking interrupts
> for this long? Writing to flash or something like that?


If everytime a byte arrives we bring up  an interrupt,that may be too
frequently for uClinux to process.



> We think that it may be caused by that uClinux's
> > speed of handling the interrupt is not fast enough to follow OS-II.
>
> First confirm what exactly is not up to speed - is it
> the kernel that fails to service the interrupt in time,
> or is it your application that is not able to take
> the data? You might want to add a byte counter into
> the kernel and to your application, send a burst of data
> and compare them - if they match, it is the kernel,
> if not, it is the app.
>
> > Does any good solution to reduce the packet-lost?
>
> Depends on the application - you need some kind of
> flow control, but a software one won't work if the
> problem is at the interrupt servicing level.



It seems that I have to try  one-byte-per-time  flow control?

Thanks .


--
>                                      Stano
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