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I trie to add a LTC2954 to the raspberry pi zero w. I designed and produced a prototype pcb with an lipo management system for load and loadsharing. My problem is, that the KILL Pin of the LTC2954 has to be set to HIGH that the power of the system keeps alive. I tried to adapt the device tree file from here. If i add the line 

pin@p20 { function = "input";   termination = "pull_up";    };

The pin is HIGH on boot if i measure it with my multimeter, but it seems that the pin is low at first because the LTC2954 kills the power short after start (the led of the raspberry just do not start to blink but i can measure 5V power for a short time)

I read that the pins 0-8 are pulled up high from the chip at boot and all other pins are pulled low at boot, if i connect the KILL to GPIO6 everything is working as it should be but i want to use the GPIO20 Pin (because of hardware design reasons).

Can someone show me how to adjust the device tree file that it is doing what i want, if that is possible with device tree?

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As far as I am aware this is not possible from device tree. Linux only has a weak understanding of GPIO.

I think the best you will be able to do is use the new gpio directive in /boot/config.txt (not to be confused with the wiringPi shell command called gpio).

Try

gpio=20=pu

See https://www.raspberrypi.org/forums/viewtopic.php?f=117&t=208748 for some details.

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  • Hi joan, thanks for your reply. I just tried it but it is the same result as before, the pin goes short down to GND and short after it goes up to 3.3V but the low time is to long the LTC2954 shuts of immediatly after pushing the button :/ – arget888 Jun 2 '18 at 8:59
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    I doubt there is a way to sort this in software. Perhaps add an external 10k pull-up to 3V3? – joan Jun 2 '18 at 10:28

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