Jan Kiszka a écrit :
> Alexandre Coffignal wrote:
>   
>> Hello,
>>
>> Thanks you for your response.
>>
>> I used this patch to communicate with a slave equipment in rs485 (modbus
>> protocol). The data is transmitted over a 2-wire twisted pair bus.
>> Master initiates all communication activity, by sending data. To do this
>> it must set RTS line to high state during all it's transmission. Before
>> slave answer, master must lower the RTS line.
>>     
>
> Will the slave wait on the deassertion of RTS? Or what will happen if
> RTS is still high and the slave starts its answer?
>
>   
No slave does not wait on the deassertion of RTS, if RTS is still high
during slave answer, it happen a collision and 
the master does not receive the frame.
>   
>> my slave equipment answer in less than 200us, so i must know when xmit
>> is completing to lower the RTS line
>>
>> An extension to RTSER_RTIOC_WAIT_EVENT may be a good solution but do you
>> know if an extension to RTSER_RTIOC_WAIT_EVENT can guarantee this timing?
>>
>>     
>
> Given a proper platform (check its capabilities with the latency or the
> irqbench test), yes. It's a myth that such things can only be done in
> kernel space.
>
> Jan
>
>   
Ok I take note of this, but do you think this function should not be in
kernel space in half duplex RS485 ?

-- 
Alexandre COFFIGNAL, Chef de Projet
Email: alexandre.coffig...@cenosys.com
<mailto:alexandre.coffig...@cenosys.com>
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