Setting a specific pin to high status when the device powered

[MarkHaysHarris777]

Hi,

I can use both 3.3v or 5V logic, I have no issue with it. It has to be high immediately when the board powered and It should go to zero when the shutdown sequence completed, then the external linbus IC will cut all the supply until it receives a data on the line.

Thanks.

Well, the question then will be whether the 0.3v that I measured when the pine64 was off (remembering that this was with nothing 'loading' the pin) is  low enough for your linbus to consider the pine64 off. It will come on and stay on (3.3v, RPi pin 1) when the the pine64 starts up, and goes off when the pine64 shuts down, so it meets those criteria.

 
Use a comparator on the PMIC output pin for DCDC1;  with an open collector, and pullup for 3v3 or 5v.

Set the threshold on the comparator for something reasonable so that the 'off' level ( .3 , whatever ) snaps the output to zero and holds it there. The LM339 is good in this kind of application.  These make great level detectors, operate at a wide voltage range, and have open collector outputs;  pullups are 'required'.