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Circuit Playground Express - additional touch sensors
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Circuit Playground Express - additional touch sensors

by JimboMusik on Thu Nov 07, 2019 2:21 pm

I am considering to purchase the Circuit Playground Express to use as a Capacitive Touch MIDI controller.

Something I'm hoping to learn first, is whether it's possible to chain it to an MPR121 or an additional Circuit Playground to expand the number of usable touch sensors.

Thank you very much!

JimboMusik
 
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Re: Circuit Playground Express - additional touch sensors

by kevinjwalters on Fri Nov 08, 2019 3:19 pm

There would be a few ways chaining the CPXs but you can also just shift the note range on a second one and have both send over MIDI USB giving 7 touch pads x 2. This works in CircuitPython but you need software that doesn't get confused by the presence of multiple USB MIDI devices with the same name, Ableton Live enumerates these well. Web MIDI in Chrome didn't like them.

There's some example code for a simple controller in Circuit Playground Express USB MIDI Controller and Synthesizer.

I've not used the MPR121 but as an i2c peripheral it should work with the CPX consuming two pads for i2c bus. The CPX pad A0 cannot be used for touch. That gives 8-1-2=5 on CPX and 12 on the MPR121. There appears to be both Arduino libraries and CircuitPython for this:


The name clashing is discussed in USB midi identification.

kevinjwalters
 
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Please be positive and constructive with your questions and comments.