On 2006-03-29, Peter Hansen <[EMAIL PROTECTED]> wrote:
>>>This seems a little odd to me. We've used several RS232-RS485
>>>converters without needing to do that. Maybe a more sophisticated
>>>device would eliminate this need?
>>
>> Yes. The device is very simple (I made it).
>
> Perhaps a very simple change to it would make it as convenient as the
> commercial products. I vaguely recall (not having checked for over a
> decade) that all they do is set the outgoing DTR line whenever there is
> data being transmitted by the PC, by using something like a 555 timer
> with a very short delay (effectively watching the start bit and any zero
> bits that are transmitted). There are probably even example circuits
> based on this or better approaches available on the net.
That approach works pretty well as long as you can tolerate an
extra byte-time delay after the last stop bit before DTR or RTS
or whatever changes state.
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