Couple of Quick Hardware Questions

[jkoffman]

Hi all,

Working through designing my first project using the Teensy 3.2 and wanted to verify a couple of things.

1. Do I need to do anything with AREF and AGND if I'm happy just using the on board generated 3.3V? Based on my read of the schematic it looks like I am clear to leave them unconnected, but I wanted to check.

2. I know that I/O pins are 5V tolerant in I/O mode, does this change at all in peripheral mode? Basically, if I'm using one of the serial ports, is RX 5V tolerant?

3. I plan on using the on board pullups. Are there any digital pins that this won't work on, or do all ports capable of digital I/O have pullups?

Thanks!

 

[JBeale]

Teensy 3.1 and 3.2 are 5 V tolerant on all digital I/O (serial port I/O is still a digital signal). AFAIK all the digital pins can be configured with pullups (or pulldowns) but I'm not the expert. If you want to wade through the Freescale manual it's probably listed there. Electrical specs: https://www.pjrc.com/teensy/K20P64M72SF1.pdf
Full datasheet: https://www.pjrc.com/teensy/K20P64M72SF1RM.pdf

 

[PaulStoffregen]

Yes, leave AREF & AGND unconnected if not using.

The digital pins are 5V tolerant, even when the peripheral is selected.

All digital pins support pullup resistors.

 

[jkoffman]

Perfect. Nice to see I'm not totally in the woods. Thanks Paul and JBeale!