[PD] Sensors

B. Bogart ben at ekran.org
Sun Nov 2 15:31:02 CET 2003

Hey Johannes,

Have you heard of the AID project? (www.interaccess.org)

We're making a GPL PIC16F877 based general sensor platform for artists in
particular. We already have 8 channels AtoD, 2 PWM ports, I2C and a 8bit bus
to communicate with up to 16 digital "peripheral" cards. Its got only Serial
interface for now, but we're working on USB as well.

I've also started a suite of control abstractions for PD, based on the
comport and ascii externals.

We're always looking for help (especially in programming- we're using hitech
C) Please jong the mailist or drop me a line if your interested in


----- Original Message -----
From: "Johannes Taelman" <Johannes.Taelman at UGent.be>
To: "Chris McCormick" <chris at mccormick.cx>
Cc: <pd-list at iem.at>
Sent: Saturday, November 01, 2003 5:59 PM
Subject: Re: [PD] Sensors

> On Fri, 31 Oct 2003, Chris McCormick wrote:
> > Hi,
> >
> > An idea I had recently (though I'm sure it's not original) is to hook up
> > 8 555-timer circuits with variable resistors to the parallel port and
> > poll it periodically to figure out the frequency of the 8 squarewaves on
> > individual parallel port pins.
> > These frequencies could be used as control values in a Pd patch. The
> > advantages are that 555 timer circuits with a variable resistor are
> > very cheap, and simple. Your range would be from where frequency updates
> > are too far between (let's say 100Hz) to the upper-range of the parallel
> > port polling frequency. So if you can poll it at 8000Hz you would
> > probably want to stop at nyquist to get meaningful updates let's say at
> > 4000Hz (not quite certain that nyquist is relevant here though).
> How about timing the pulse width (from the capacitor discharges) directly,
> instead of counting the frequency? The legacy joystick port works this way
> (also using polling).
> Still, if you want to build your own sensor-to-pc interface, I think using
> a microchip PIC microcontroller (on serial port, on a MIDI port, or the
> USB-series) for analog inputs is a more elegant solution. It requires the
> use of a programmer once though, but those are not expensive either. It is
> less components, less handwork, less CPU cycles wasted on polling, and
> more resolution. Have a look at www.ucapps.de for a well-documented and
> free design.
> I started messing with those chips a couple of months ago, and I'm pleased
> with them. I've programmed them for analog-to-midi, as a 12-channel
> infrared-light-barrier-controller and as multichannel pulse generator.
> regards,
>  j#|@
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