Re: RS485 implementation questions (primarly in atmel_serial.c)

[Grant Edwards <grant.b.edwards@gmail.com>]

On 2013-01-30, Jean-Pierre Tosoni <jp.tosoni@acksys.fr> wrote:
>
> Well, you need to ascertain that the previous frame is all out AND
> the RTS has dropped before sending a new frame. Else the receiver
> might think it is the same long frame. Using TXEMPTY interrupt avoids
> setting an extra timer. However in the real life you are half-duplex
> and never send two frames in a row without waiting for an answer.
> Other than that I agree with your remark.
>
>> rare.  But this function is not especially related to RS485. It is
>> also applicable in RS232 mode.  So in my view it is not the
>
> True, it applies to some half-duplex RS232 radio modems too AFAIK.

It applies to half duplex modems and line-drivers whether they're
radio or not.  Believe it or not, Bell-202 half-duplex over plain old
copper wire is still used a lot in the process control industry.

But, because of the general brokeness of both Windows and Linux serial
drivers when it comes to half-duplex communications, many of the
Bell-202 modems sold these days have automatic tx data detection and
handle the "RTS toggle" function themselves.

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