Teensy 3.0/3.1 reset pin assertion

[Epyon]

Hello all

I have an application where a Teensy 3.0 or 3.1 will be placed on another PCB containing some other digital logic. Both the board and the Teensy share the reset line, so both are reset when the line is pulled low.

However, the expansion board keeps the reset line pulled up to 3.3V when not in use. Is this a problem for the Teensy? Can I apply 3.3V safely to the reset pin of the Teensy?

In the K20 manual, I also found this:

Keeping the RESET pin asserted externally delays the negation of the internal Chip Reset.

Does this mean this could mess up chip reset when uploading new firmware?

Thx!

 

[PaulStoffregen]

Can I apply 3.3V safely to the reset pin of the Teensy?

That's not recommended. It's best to only pull the reset line low (eg, a pushbutton or an open collector drive).

Does this mean this could mess up chip reset when uploading new firmware?

The Mini54 chip will pull the reset line low, so yes, you could conflict with the Mini54 if you're actively (not just a weak pullup) driving the reset line high. Definitely not recommended.

 

[Epyon]

Thanks for the information Paul. Would a small diode circuit like this do the trick?
TRESET = reset pin of the Teensy
RESET = reset pin of the shield