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Re: RS 485 with Fast Timer API ???



Christian Hoffmann [Niechoj electronic GmbH] wrote:

> Hi there,
> 
> i have to communicate over 2 wire RS 485. I use the 485 implementation 
> and it is working fine. But i need to have to set the RTS line high 
> about 2 ms before sending and set it low  2 ms after sending.
> I enabled the fast timer with xconfig and used "make kernel" and tried 
> my program again. But then before anything is sent i got this kernel panic:
> 
 > <snip ....>

I have no ideas why your kernel crashes, mine never did. BTW the
kernels on the devboards I've received already have fast timers enabled.

I've managed to communicate over 2 wire RS485 at 115200 baud, but
had a little problem releasing the RTS line fast enough to prevent
the response from the other device to start communicate before the
RTS line was low. But at 9600 baud I don't think you should have that 
problem.

You say that you should set the RTS line 2 ms before sending.
Maybe your receiving device is able to handle if you start by
sending 2 0xFF's or 0x00's. Mine are :-)

Best regards
Steen Jansdal