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MartinKeppler

Power Management Banana Pi

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Hi specialists,

 

I'm trying to understand how the axp209 on Banana Pi works with the A20.

In the Banana Pi schematics I see, that they are connected with only four lines. Two lines are used for I²C (TWSI), one is from axp209 PWROK to RESET# of A20 and another one is connected from axp209 IRQ and GPIO2 to NMI# of A20.

 

When system is off and I press my Power Button (K1)  on the Pi, the system is booting. System is running and I long press the Power Button, System shuts down. But can anyone say whats happening? What does axp209 do with IRQ, GPIO2 and PWROK pins? Wich way does the A20 recognize, that it has to shutdown?

 

Yours Martin

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You can find some info and datasheet here: https://linux-sunxi.org/AXP209

Section "Control and operation" in the datasheet should answer most of your questions.

 

When system is off and I press my Power Button (K1)  on the Pi, the system is booting.

AXP209 comes from standby and enables all necessary regulators to boot the board

 

System is running and I long press the Power Button, System shuts down. 

AXP209 processes long press and shuts down most of regulators

 

What does axp209 do with IRQ, GPIO2 and PWROK pins? Wich way does the A20 recognize, that it has to shutdown?

AXP209 IRQ output is connected to A20 NMI input, this way it can send power related events to the CPU.

In case of short power button press, AXP209 sends an IRQ to the CPU, and the kernel driver exposes this as a press of power button of a virtual input device.

In case of long power button press, A20 doesn't have a choice - AXP209 will simply cut off the power.

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