Teensy 3.1 and 5V Analog input

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mummyboy

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According to PJRC ...

"Today most new chips use 3.3V signals, but many legacy products output 5 volt digital signals. These can now be directly connected to Teensy 3.1's digital inputs.
All digital pins are 5 volt tolerant on Teensy 3.1. However, the analog-only pins (A10-A14), AREF, Program and Reset are 3.3V only. "

The primary components of my project are a Teensy 3.1/Octows2811 combination and a nominal 5v 350W/70A power supply and 796 5v ws2811 LEDs.

I have 5 nominally 10K potentiometers (installed on pins A5, A4, A3, A11, A10) which are currently supported (no pun intended!) with that 5.v input. I haven't tested yet but after coming across the preceding PJRC caveat I'm left wondering how to proceed:

  • Will I fry the Teensy with 5v to the pots/analog inputs or will the pot readings simply be unreliable (or will it just magically work)?
  • Do I merely need a current limiting resistor in the 5v power line to achieve the 3v max input for the pots/analog pins?
  • If yes to above, what value resistor will I need (I know the voltage, natch, but not the current, I don't think)?
  • Is there any advantage to reduce the voltage to 3v for the digital pins too?


still learning

mb
 
From previous postings, A10-A14 are NOT 5v tolerant. If you plug in 5v to those pins, you will likely fry your Teensy. A0..A9 are 5v tolerant, but any voltage over 3.3v is treated like 3.3v and returns 1023.
 
Run the pots from 3.3V pin available on the Teensy. If they are just input there is no reason to run them from 5V.
 
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