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I'm using one as part of a midi controller project: http://jsnow.bootlegether.net/jik/keyboard.html http://jsnow.bootlegether.net/jik/keyboard.html The contro
by elihu 7y ago
I'm using one as part of a midi controller project:
http://jsnow.bootlegether.net/jik/keyboard.html http://jsnow.bootlegether.net/jik/keyboard.html
The controller has 156 pressure sensitive keys. The raspberry Pi runs a program that reads from a bank of 20 8-channel ADCs all wired up to a SPI bus (it runs at 2mhz, and I'm able to get about 90 samples per second), and then generates MIDI commands that are sent over a USB-MIDI adapter.
I could use a microcontroller for this, but it's kind of convenient to be able to plug other USB-MIDI devices into it and have it work, and to be able to run a Linux-based synthesizer locally if I want. (I've been planning on using a Teensy for the next version.)
- oddsockmachine 7y agoThanks for sharing this, it's great to see your process. I'm working on something vaguely related, a grid-based synth-controller/sequencer with a bunch of i2c shift registers and laser cut hardware. I've been thinking about building a pressure-sensitive hex-layout keyboard next, you've given me a bunch of ideas and inspiration.
- elihu 7y agoThanks. Pressure sensing is actually pretty simple and cheap, unless you have a really large number of inputs (like I have). I was planning to switch to a matrix layout in the next version to reduce the number of ADC chips I need, but then I'll have to figure out how to mitigate ghosting. I haven't used any of Sensitronic's producs, but they do have a lot of good information on their site about the various ways to use force-sensitive resistors.