I want to use four teensy boards connected via the I2C protocol over a short distance (not more than 0.5m or 20 inches) but only the master one powered by the USB cable.

Should that be safe to connect the Vin pins of the slaves to the 3.3V pin of the master? (provided that the total amperage doesn't exceed the maximum).

In that case should I connect all boards to GND instead of AGNG? (no analog conpontment is included).

Thank you in advance.

  • \$\begingroup\$ Which Teensy board are you talking about? pjrc.com/teensy/schematic.html \$\endgroup\$ Commented Dec 16, 2019 at 17:57
  • \$\begingroup\$ That would be teensy 3.2 as master and teensy LC as slaves \$\endgroup\$ Commented Dec 16, 2019 at 18:05

1 Answer 1


Given your clarification that the Master is a Teensy 3.2 and the Slaves are Teensy-LC you should NOT connect the 3.3V output of the master to the slaves.

Referring to the two schematics you will see that in the Teensy-LC the 74LV1T125 is powered from the Vin (+5V) so this devices would be un-powered if you only connect 3.3V rails.

The best option would appear to be to connect the Vin from the Master to the Vin of the Slaves and the GND pin from the Master to the Slaves (don't use AGND as it's connected through Ferrites to GND).

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NOTE: The Teensy-LC processor has an built in 3.3V regulator, so powering the Vin pin with +5V is the best solution.

  • \$\begingroup\$ I am confused. I thought that the Vin pin acts only as power input. Does that act as output as well? \$\endgroup\$ Commented Dec 17, 2019 at 5:56
  • 1
    \$\begingroup\$ @user3060854 Yes ...of course it can be an input OR an output from the Master. Follow the line back to the USB connector.......in this case your Master is fed from a USB source, or you could power the Master with a power supply or battery source. \$\endgroup\$ Commented Dec 17, 2019 at 16:46

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