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

[Stanislav Meduna]

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.

> 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 ;)

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?

> 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.

-- 
                                     Stano