On Fri, 31 Oct 2003, matthew jones wrote:
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!
Soundcards filter out all dc ("constant bias") on their inputs. You will not get good measurements from unmodulated, slowly ( <10Hz) varying signals. You could modulate the sensor signal in some way, but this requires more analog electronics.
am I mistaken? has anyone used this to good effect?
Yes, I've used a soundcard to sample ultrasound (sonar) receivers directly. This is (in my case) a 40kHz modulated signal. This shifts the demodulation from hardware to software... So 96kHz is usefull - not only for audiophiles :)
best, Johannes