Noob question - teensy 3.5 Midicontroller

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Gripporillat

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Hi there!

First of all I'm a total Microcontroller-Noob. It's my first Teensy project. I want to build a simple USB Midicontroller with faders and push buttons. I'm considering Teensy 3.5 since it seems to have most inputs. As far as I understand it, I can use 27 analog inputs for 27 faders, right? What I don't understand is: if I use all those 27 inputs for faders - how many inputs I can use for push buttons?

Second question: Which of the pins are the 27 analog inputs?

Sorry for being such a beginner.

Thx in advance
Robert
 
You can see the pin assignment here:
https://www.pjrc.com/teensy/pinout.html

Next to each pin diagram there are various colors indicating what type of "function" this pin can have. Grey fields are for digital and peach colored fields are for analogue. So a lot of pins on the Teensy 3.5 can be used for either digital or analogue and some only for digital.

Some of the pins are on the underside of the board, so when you plug the Teensy into a breadboard, those pins will no longer be accessible unless you solder to those pads via wires. Some people have made shields that make those pins available via lateral breakouts.

Once you run out of pins you will need to use multiplexer chips. Scroll down on this page to read a bit more on how that works (Connecting Many Buttons & Knobs/Sliders):
https://www.pjrc.com/teensy/td_midi.html
 
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How many controls you can support with a T3.5 depends on how many of the signal contacts you are cable of connecting to.

There are pad contacts on the back but my soldering skills leave them off limits...

You might consider a small MIDI project to start unless you are already competent building electronic circuits.

Are you interested in learning to code or more in the build?
 
Once you run out of pins you will need to use multiplexer chips. Scroll down on this page to read a bit more on how that works (Connecting Many Buttons & Knobs/Sliders):

Does this basically mean I can theoretically connect an infinite number of buttons and sliders as long as I don't run out of space?

oddson said:
Are you interested in learning to code or more in the build?

This is part of a bigger project and I'm on a tight schedule so unfortunately I can't dig to deep into it. But of course I'm willing to learn what it takes to finish my project.
 
Does this basically mean I can theoretically connect an infinite number of buttons and sliders as long as I don't run out of space?.

Quite a few I guess but at some point the latency on reading the various input button / faders will get too high depending on your use case. Also, the more you add, the more you will have to deal with circuit complexity etc. Another way is using multiple Teensys in a master - slave configuration where each slave deals with a set amount of faders / buttons and then passes the read outs to the master Teensy via a serial link or other.
 
Test.jpg

Would it work like this?
 

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That should work, assuming the pin labeled "E" is really "3".

However, you will need pinMode(3, INPUT_PULLUP). Because the built in pullup resistor is weak, you will need to add a delay of many microseconds after changing the mux, before you actually read pin 3.

To work faster, you could add 8 real pullup resistors to the buttons. Likewise, for the pots use 10K or 5K. Higher impedance are more susceptible to noise and require longer delays.
 
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