RE: Caller ID unit.

["Ian Davidson" <ian@xxxxxxx>]

Hi Stuart

If I have read the data sheet correctly you can not do what you want. In
Jon's circuit the IC in use does output async 1200 baud data but at 5v
levels and he uses a level converter to increase these to proper RS232
levels (+/-12V) which can then be fed to a PC.

The Mitel chips output is not async but is clocked out with the start
and stop bits removed (just the data bits). A small micro could easily
decode this but it is not suitable for the input of a PC RS232 even when
level converted. The only solution would be to but a small micro in
there (read PIC) to re-insert the start and stop bits and then level
convert but it is probably not worth it.

Sorry to put a dampner on it Stuart but hopefully save you some time and
effort.

Regards

Ian D


-----Original Message-----
From: Stuart Grimshaw [mailto:stuart@xxxxxxx]
Sent: 02 July 2003 09:03
To: UKHA List
Subject: Re: [ukha_d] Caller ID unit.

On Wed, 2003-07-02 at 00:20, David Gumbrell wrote:
> Well, you beat me to it then.
>
> The Mitel (MT88E43BS) is the chip with the RS232 almost compatible
output.

Pin 17 of the chip is data out, (5th up from the bottom right) but at
CMOS level rather than TTL.

Jon Payne's circuit
(http://www.photon.dyndns.org/projects/btcd50conversion/index.html)
uses
a MAX232 chip to convert to RS232 (hint, get a free sample of them from
www.maxim-ic.com), the data sheet for which says input is either cmos
compatible.

Can someone confirm that Jon's circuit will work with CMOS level input?



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