The Pi4 J2 Header

Building Zynthian
1

image

https://www.raspberrypi.org/forums/viewtopic.php?t=243488

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. . . .

2

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…

3

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.