[PD] Sensors

matthew jones M.Jones at signal.qinetiq.com
Fri Oct 31 15:29:54 CET 2003

I really don't understand why people are so hooked up on using MIDI or
serial/parallel ports for interfacing sensors with pd.  It strikes me that
the absolute best way if you are at all worried about sample
rate/quantisation amount is to use the audio signal inputs of your
soundcard.  some simple circuitry and then you have maybe a 96kHz 24bit
input - super fast control and with same latency!

am I mistaken? has anyone used this to good effect?  I was thinking that the
terminatorX style turntable things are a prime example of where a mouse just
doesn't offer enough resolution to do even a half decent job....


----- Original Message -----
From: "Marc Lavallée" <odradek at videotron.ca>
To: <pd-list at iem.at>
Sent: Friday, October 31, 2003 2:01 PM
Subject: Re: [PD] Sensors

> On Fri, Oct 31, 2003 at 09:25:34PM +0800, Chris McCormick wrote:
> > 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).
> Interesting, but I'm not sure it's possible to poll the parallel port as
> fast. With my parapin object, I use 1Khz by default, which correspond to
> the maximum resolution of timers in PD (but I might be wrong).
> http://www.pure-data.org/Members/odradek/parapin
> --
> Marc
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