RE: RS485

["Timothy Morris" <mail@xxxxxxx>]

I *think* it does do hardware handshaking. If I send data to the PC when
asleep, and then manually wake it up, the commands are executed after it
wakes up. The question in my mind is that if I do link RTS with RI, would
it
affect normal operation? I remember when I first started working for an ICL
trader selling Unix boxes spending several hours with a soldering iron and
a
breakout box tyring to get serial cables to work!

Tim.

-----Original Message-----
From: Steve Morgan [mailto:steve@xxxxxxx]
Sent: 11 April 2000 09:05
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] RS485


I sincerely doubt if this would work.

With a modem, the ring signal is generated before the modem answers the
call. This allows time for the PC to wake up before the call is answered.
In
addition, the use of hardware handshaking means that data won't be sent by
the modem until the PC is ready to receive it, being buffered in the modem
until such time.

Attempting to tie together the RI and RX pins would mean that the PC would
be waking up as the CM11 transmits the data. I suspect that the possibility
of lost data is high. I also can't remember off the top of my head if the
CM11 uses hardware handshaking. If so, it wouldn't transmit any data since
there'd be no CTS.

Hang on, though....

Supposing you tied RTS and RI, so that a ring is generated when there is
data to send, rather than when it is actually sent?

This would obviously only work if the CM11 does use hardware handshaking
and, as I said, I can't remember.

What does anyone else think?

Steve

> -----Original Message-----
> From: Timothy Morris [mailto:mail@xxxxxxx]
> Sent: 10 April 2000 22:12
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] RS485
>
>
> Maybe you can answer a question for me then :)
>
> I want to use ACPI to put my machine into standby when idle.
> I have two
> problems to overcome - the first is that my PC is used for Fax and
> answerphone through ISDN, and the second is that I use
> Homeseer. I have
> found a solution to the first - AVM are releasing a USB TA in
> a couple of
> months which will wake the machine up. The board will 'wake
> on ring'. Would
> it be possible to bridge the RX data and Ring pins (whichever
> they are on a
> 9-pin COM port) - so that when the CM11 sends data to the PC
> it is woken up?
>
> Tim.
>
> -----Original Message-----
> From: Steve Morgan [mailto:steve@xxxxxxx]
> Sent: 10 April 2000 22:01
> To: 'ukha_d@xxxxxxx'
> Subject: RE: [ukha_d] RS485
>
>
> I bought a useful book through Amazon called
>
> Serial Port Complete by Jan Axelson
> (ISBN 096508192-3 - it's here in front of me, I don't memorise this
> stuff!)
>
> Includes lots of good stuff about RS-485 including connecting Basic
> Stamp's and PC's
>
> Cheers,
> Steve
>
> -----Original Message-----
> From: Jon Whiten [mailto:jon@xxxxxxx]
> Sent: 10 April 2000 20:15
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] RS485
>
>
> Not specifically UKHA related but...
>
> I am wanting to read up about RS485 (how it works, how to connect
> devices to
> it, etc) and wondered if anybody had any pointers they were willing to
> share?
>
>
> Regards,
>
> Jon
>
> +--------------Personal------------+----------Work-----------+
>  Jon Whiten        Church Gresley   D.G. Controls Limited
>                        Derbyshire  Beacon Lamp Specialists
>  jon@xxxxxxx         England    mail@xxxxxxx
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