Core Electronics Forum

Raspberry Pi 3B+ - PEN & RUN Headers clarification

Can anyone please clarify the correct use of PEN & RUN header on the new 3B+ board.
I’m reading a lot of old references to the RUN header on the old 3B as a reset for system halted.
Thanks

Hi Trent,

The PEN header is for Power ENable. When this pin is connected to ground, the Pi goes into its lowest possible power state (I measured 0.01A). It is effectively just running the red LED at this point. Removing this ground connection causes the pull-up resistor on-board to pull this enable pin HIGH, giving the board power again. This could be attached to a low-power microcontroller if you needed a remote wake-up for instance.

The RUN header is similar, but for the CPU only. Connecting this to ground stops the CPU from running, but the Pi board still has power (I measured 0.10A, the same as when the Pi is shutdown with the menu). This is what you could use as a “reset switch”.

Does that answer your question?

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Perfect. Thanks
Felt like it was going round in circles looking for the difference.

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