multiple teensy on one board

[snowsh]

I am working on a project that now requires two or more teensy 4.1.

I have not yet decided on how to communicate between them. Serial UART or i2c maybe... My question is about power. 3v3.....

TEENSY 1:

So TEENSY 1 (plugged into usb) can take power either over USB, but most likely I will ditch that and go with a separate wall wart @9v feeding a l7805 5v regulator and relevant smoothing caps / diode protection...

I take 3v3 from TEENSY 1 to run things like buttons and pots that hook to TEENSY 1. This is the main board.

The board has an expansion connector that takes unused pins and other lines to optional breakout boards. This is where the potential 2nd or more teensy will sit.

TEENSY 2:

I intend to run this solely off the internal 5v line from my L7805 regulator on the main board. but heres the thing.... I also have a 3v3 line from TEENSY 1 being passed to the breakout board. Should I isolate the 3v3 lines on the breakout board to only pull 3v3 from TEENSY 2 which is powered by the global 5v line and of course TEENSY 2 has its own 3v3 regulator....

Am I going to run into issues if the 3v3 line from TEENSY 1 connects to the 3v3 line of TEENSY 2?

 

[KenHahn]

You need to keep the two 3.3V Teensy regulator outputs isolated.

A 3.3V regulator on your baseboard would help to remove the load off the Teensy regulators and would provide a little more protection for the Teensy if you're not sure what all you may be powering from 3.3V on the expansion bus.

 

[snowsh]

You need to keep the two 3.3V Teensy regulator outputs isolated.

A 3.3V regulator on your baseboard would help to remove the load off the Teensy regulators and would provide a little more protection for the Teensy if you're not sure what all you may be powering from 3.3V on the expansion bus.

ok yes that is what I was thinking. I intend to commnicate between the two teensy. Are there issues connecting pins if they are powered separately?

 

[XFer]

No issue, provided the two "3.3v" levels are within Teensy tolerance (i.e.: A=3.2V and B=3.4V are OK).
The (digital) GNDs have to be common.