Arduino Mega 2560 — expand I/O with 4051 Analog Multiplexer?

[stllvdv]

Hey there,

Please correct me if necessary, I'm not sure I got that right:

a) the OpenDeck firmware not only runs on the official boards, but also supports something like the Arduino Mega 2560? b) I wonder if it's possible to expand the 16 analog inputs of an Arduino Mega 2560 with one or more 4051 analog multiplexer/demultiplexer units? Surely 8 additional inputs for each of the 16 analog inputs would create quite a few possibilities for many, many potentiometers.

Warm regards.

[paradajz]

a) the OpenDeck firmware not only runs on the official boards, but also supports something like the Arduino Mega 2560?

Yes.

b) I wonder if it's possible to expand the 16 analog inputs of an Arduino Mega 2560 with one or more 4051 analog multiplexer/demultiplexer units?

Yes.

However, instead of Mega I really suggest using Raspberry Pi Pico because:

• it's cheaper
• it's smaller
• it's easier to flash
• it has loads of flash memory so it supports 10 presets
• the latency is better (on Mega everything goes through ATmega16u2 MCU which acts as an USB interface)

[paradajz]

Multiple MCP 23017-E/SP

No, not supported. Read the entire page to see what's supported: https://github.com/shanteacontrols/OpenDeck/wiki/Creating-custom-board-variant. 4067 is supported yes.

3rd party extension boards aren't supported.

adding new general purpose IOs means that those can be used for either digital or analog inputs?

No.

[stllvdv]

@eurorackworld Just seen RPI Pico W + 4067 multiplexer where you commented as well. Was wondering if there's anything you could share in case I need help? Will probably try to add a few 4067 to the RP2040, looking for 48 (maybe 96) analog inputs (not sure how many digital inputs == switches/buttons I'll need).

[stllvdv]

Okay, slowly but surely getting into this, but some things are still confusing the heck out of me. I've now received a Pico, flashed it, works great; now what do I have to do to create a custom board variant with expanded analog input capabilities? Two goals: a) expand with a single 4051 for 8 inputs b) expand with 3x 4067 or more once I get the basics…

– get the packages, then clone the repository
– apparently update cmake as my version is always obsolete
– connect a MUX of choice correctly
– configure the YAML correctly
– build a new UF2 with make TARGET=my_custom_conf and flash

I kind of get how I have to connect the MUX in general, but the devil is in the details I guess. For starters: how do I know where on the PICO I have to connect s1, s2, s3, (s4) and z0? Which GPIO is which? How do I define these in the YAML? I've seen the examples in the docs, but don't quite get it yet…

EDIT: Can I simply define those myself?

[stllvdv]

@paradajz Still exploring how to set up the config-files properly, but just ran make TARGET=pico in the meantime to get the hang of it all. This creates a folder in build with various files and subfolders. Final step would be renaming application.elf.bin to e.g. pico.uf2 to be dropped to the PICO?

[stllvdv]

OK! Got the PICO and 1x 4067 working! Next goal/mystery: c) shift registers I guess to add… maybe 20… buttons!

[stllvdv]

Thanks! Love the project, brilliant! I'll be sure to look into that RP2040 as well then.

[paradajz]

For starters: how do I know where on the PICO I have to connect s1, s2, s3, (s4) and z0? Which GPIO is which?

You pick any pin you want.

Final step would be renaming application.elf.bin to e.g. pico.uf2 to be dropped to the PICO?

Not sure where you got this idea from? The build system creates uf2 file called merged.uf2 in the build directory.

[stllvdv]

a) Any pin? Interesting… b) Doing all of this for the first time, might have misunderstood "Build process creates binaries in build directory" and my mind connected binaries to .bin — completely overlooked that a .uf2 is created as well.

[stllvdv]

[paradajz]

Pull the latest master branch and try again, just run make clean first.

[stllvdv]

Thanks — make clean changes everything.

[paradajz]

It's mentioned in the wiki as well:

https://github.com/shanteacontrols/OpenDeck/wiki/Creating-custom-board-variant#building-custom-configuration