Raspberry Pi Pico with Multiplexer, 8 Fader and 4 Buttons

I tried to build a Raspberry Pi Pico with Multiplexer, 8 Fader and 4 Buttons

Would this work like seen in the screenshot?

It doesn’t seem likely to work, no. Pin 37 for instance is not 3V3 out but a control signal that enables 3V3 output, pin 36 is the 3V3 output. The Pico has no visible power (although it may be powered via the USB port), The EN pin on the CD74HC4067 needs a connection somewhere (in general CMOS doesn’t like floating pins) and channels 7 through 15 likely need to be grounded. GPIO10 is not an ADC pin and likely won’t accept an analog input (which it is currently getting.) There is no indication of where the output from this may be (not that it matters a lot until the other problems are fixed!) So my assessment would be it is unlikely to work for any reasonable value of work.


Hi DeepBlueMind, Peter,

Here some links to start reading from Sparkfun :


OK, I updated it and I hope, this time it should work

Looks better (although there is still no output unless that comes from the software somewhere) and you may need pull up resistors on the push buttons (or to enable the internal pull up resistors, if there are any, there are on the Arduino but I’m not sure about the pico!) on the push button input ports.


I am trying to build something like this:

just with an Pico Pi


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That should work fine if you add a Midi port for the output which isn’t yet present. That would cure the lack of an output.


Why di I need a Midi Port? Midi would be sent internally, or am I wrong?

In the FADR-4 there is also no Midi Port

I don’t know that much about MIDI, but my understanding from other MIDI projects I have seen would be that you need a MIDI connector to connect it to other midi devices. It may be able to connect to other devices via wireless (if the pico supports wireless) but it needs a connection of some kind to other MIDI devices I would think. Presumably the sound that you are fading is coming in from some other MIDI device and presumably needs to go somewhere to be heard since there is no input or output on your project.


The code for the referenced project is using a ‘usbMIDI’ object. I did not see where that is created, but it appears to be intended to control the midi over usb. No explicit MIDI port needed. I do know know how that works.

If @microMerlin is correct (which he probably is) they are communicating via USB. Your problem then becomes if the pico has a suitable USB driver (or needs a special one!) I didn’t know that MIDI would go across USB but there is no reason that it couldn’t. It may use a standard interface (and thus just work) or it may need a special driver.


Hello DeepBlueMind have you seen this opensource software that will run on a pico to make a midi controller? I’ve used it to make a 3 fader controller with a Pico. You can edit the YAML code to add a multiplexer. Although that is beyond me!


Oh nice - gonna look into it!
Thank you very much!!! :slight_smile:

If you work out how to build the code for a pi including the multiplexer please could you share it with me. :slightly_smiling_face:

If I ever be able to work it out, I will! :wink:

About 8 posts up from the bottom of this thread user MarkoKovachki-Starloop has posted a file called Pico configs. In there are a few .uf2 files which you just drop onto a pico to program it. There is also YAML files which give the pin connections for the multiplexer.

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I wanted to note that the pi pico has internal pull-ups.

And, on the usb midi front, todbot has both circuitpython and arduino c examples for midi sequencing in seveal projects, for instance: