Can a Teensy MicroMod analog pin withstand a "5v" MIDI signal?

[isaacjacobson]

PROJECT DESCRIPTION
So I have a project with a Teensy MicroMod. I want to incorporate MIDI IN and EXPRESSION via a single 3.5mm TRS jack. There is a 3PDT switch that changes the 3.5mm TRS jack circuit from MIDI and EXPRESSION inputs. While in "MIDI Mode," the TRS goes to the Teensy MM RX0 pin (via a standard midi standard circuit). While in "Expression Mode," the TRS input sends to A2 pin (via standard expression pedal/potentiometer circuit).

MY QUESTION
So what happens in the unlikely event that I accidentally send a midi signal while it is in "Expression Mode"? Aka... what happens if I send a the MIDI output of a midi device/controller DIRECTLY to the A2 pin?

I've heard that some older midi devices are 5v, and my understanding is that the Teensy MM doesn't withstand higher than 3.3 on the pins. Is my Teensy MM in trouble? Would it get overpowered? Or are 5v MIDI signals so obsolete that I don't have to worry about it?


I'd greatly appreciate hearing some thoughts on this!

 

[neutron7]

I have used MIDI on a few projects, I run the MIDI opto isolator on 3.3v so teensy voltage level is not a problem. Another trick is to use a rectifier so that either of the TRS MIDI "standards" (sometimes called A and K, for arturia and korg) will work. diodes are bat54s (the "s" is very important!)

 

[isaacjacobson]

I have used MIDI on a few projects, I run the MIDI opto isolator on 3.3v so teensy voltage level is not a problem. Another trick is to use a rectifier so that either of the TRS MIDI "standards" (sometimes called A and K, for arturia and korg) will work.View attachment 29180 diodes are bat54s (the "s" is very important!)

Thanks a ton for the great idea. I'm new enough to this that I never even thought about that!

Would you mind looking over my circuit below and letting me know whether it's correct? I used this for the diodes. And this for the opto.





The "MIDI_RX" is to the RX0 Pin. "USB_VIN" is (obviously) 5v.

This is with a Teensy MM if it makes a difference.

 

[neutron7]

That seems right, except I power the optoisolator from the teensy 3.3v rather than vusb, just to be sure no 5v can reach the teensy. I dont even know what will happen when you use a pull up to a different voltage than the chip supply, it just has a simple opto transistor inside.