The Pi4 J2 Header


The RUN signal allows the Pi SoC to be reset,
the EN allows the PMIC to powered up and down.

the EN pin connected to 5V via a 100K 63mW resistor, RUN to 3V3 via 10K 63mW.

Update : From a Raspberry Pi engineer, the answers to the questions are as follows:

  1. Momentarily short GLOBAL_EN to ground to restart a halted RBP4.

  2. Momentarily short GLOBAL_EN to ground to restart a running RBP4. Usual caveats about suddenly powering off your system apply.

and something that made me laugh. . . .

Well it makes a little more sense now .

I can reboot the zynth from the ENABLE PIN and also reset it. BUT the 7" touchscreen does not reset simply goes stripey. The Pi reboots, indeed, I can find it on vnc and it’s makes noises properly, but no touchscreen without poweroff…

ok. Powering the Touchscreen from a separate power supply via the small usb connector on the touchscreen allows a shutdown to be produced.

Press and hold reset button ( connects J2 ENABLE to OV )
Disconnect Screen power supply.
Reconnect screen power supply.
Release reset button

So I need a mechanism to perform this merry little dance.