Re: H/W Development question

["Patrick Lidstone" <patrick@xxxxxxx>]

If you are looking at monitoring the state of a limited number of 
outputs (say up to 3 or 4) this can be done via the serial port with 
no additional hardware - the CTS, RI, and DSR lines can all be 
connected direct to a 12V output and their state determined 
programmatically.

You can do similar tricks with the parallel port, but they operate at 
TTL (5V) levels.

Patrick


--- In ukha_d@y..., "Dave McLaughlin" <dave@v...>
wrote:
> Hi Robert,
> 
> This is easy with the likes of the PIC or AVR microcontrollers. A 
simple
> transistor, a couple of resistors and you can detect the state and
send an
> RS232 command to the PC. You can could buy an off the shelf module
such as
> the Basic Stamp as this would be the quickest way to get it working
if you
> don't have any PIC or AVR dev kit. Check out www.milinst.com for 
the BS2 dev
> kit. Might be higher in cost than the likes of the VIOM module from
Phaedrus
> (http://www.phaedrusltd.co.uk/system/index.html)
but you will 
easily find
> other interesting projects to put the stamp to good use with. The 
VIOM is
> also quite large compared to the stamp.
> 
> USB is harder but not difficult. Check out the last few issues of 
Elektor as
> there was an article about using the Cypress USB controller. A mate
is
> currently trying it out and is most inpressed so far.
> 
> Good luck
> Dave...
> 
> 
> ----- Original Message -----
> From: "Robert Welsh" <bob-ukha@s...>
> To: <ukha_d@y...>
> Sent: Friday, December 06, 2002 9:48 AM
> Subject: [ukha_d] H/W Development question
> 
> 
> > One for the hardware techies out there...
> >
> > I discovered last night that my alarm system has a number of 
output
> > terminals which can be use to drive external devices e.g. ARC
or
> > diallers.
> >
> > One of the terminals is a "set" indicator - which is
exactly what 
I'm
> > looking for.
> >
> > This terminal is 12V normally and drops to 0V on "set"
condition.
> > There's also a 13V and a 0V terminal offered on the PCB.
> >
> > What I'm not sure is how to start designing something simple that
I
> > could connect to a serial port to monitor this.
> > It seems to me that it's probably the kind of thing that must
have been
> > developed 100 times by 100 different people.
> >
> > Any pointers would be appreciated.
> >
> > Robert

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