linux usleep

[xhjin]

dear sir,

can you help to solve following problem??

I am using GCC to port  RS485 device driver, but i encounted a serious problem.

In my program code, i should get a micro second level delay and called the
function usleep(1000) for delay 1 ms, but can't get the
result. i got the waveform using scope, but can only get a delay for at least 20
ms, no matter how chang the value.

i tried to modify the HZ value in <asm/param.h>, but also the same ...

Dear sir, another question irritate me from compille warning:   implicit
declaration of function 'usleep'
it just happened after i modified the <asm/param.h> and compiled the source
code. And make me puzzled is that i
can't restore its previous status (no any warning).
what can this happen? i have alread added the header files. BEFORE , no this
warning exist!!

dear sir, please give me hint, it is urgent for my project.

Thank u very much.

Jin Xinhua

R&D
GES Singapore Ptd Ltd