Are Teensy 2.0 pins 5V tolerant?

[joe_prince]

I can't seem to find the answer online, but wondering if the Teensy 2.0 digital input is 5V tolerant or 3.3V tolerant? Also, for I2C communication would I need to level shift a 3.3V slave signal up to 5V for the Teensy 2.0 to read a logic high?

When I connected the I2C lines of a 3.3V slave directly to the Teensy 2.0, communication seemed to work fine without doing level shifting. I'm not sure if it was just "luck" that it was seeing the 3.3V logic levels as high though.

 

[MichaelMeissner]

I believe unless you modify it, the Teensy 2.0 runs at 5v. I would check if the device you are connecting to the i2c is 5v tolerant. If it isn't, connecting it to a 5v Teensy 2.0 might let out the magic smoke.

In terms of Teensy 3.x/LC, the 3.0 and LC are NOT 5v tolerant. The 3.1 and 3.2 can receive 5v signals on the pins that can do digital input/output. However, some of the analog pins are not 5v tolerant. Also, if you do an analogRead of a pin that can handle 5v, it will clamp the voltage at 3.3v.

 

[joe_prince]

I believe unless you modify it, the Teensy 2.0 runs at 5v. I would check if the device you are connecting to the i2c is 5v tolerant. If it isn't, connecting it to a 5v Teensy 2.0 might let out the magic smoke.

So was it just coincidence that the 3.3V signals sent from the slave communicated fine? Would it be safer to level shift the signals to avoid any accidental missed high readings?

 

[MichaelMeissner]

Yes, in general you should always make sure both sides agree on the voltage.

 

[joe_prince]

Thanks Michael.

I just hooked up a potentiometer (outputting from 0 to 5v) to one of the pins and performed a digital read, and it looks like right around 1.5V it transitions from a logic low to a logic high. The ATmega32u4 datasheet has a max Vil of 0.2Vcc - 0.1V (i.e., for a 5V system a 0.9V for LVTTL).

Looking at this chart (http://forum.allaboutcircuits.com/p...ing.png&hash=0b8e23fd5ac977991da789adbb4f0a27) it appears to check out.