current enhancement after shutdown

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I'm currently facing strange problems...


I'm using NanoPi M4 and operate a USB camera with it.

Since I wanted to know the total power consumption of the system, I measured current which flows into NanoPi from the outlet.

(I used GPIO to supply 5V power this time for some reasons)


The current during while the camera working was very nice (about 1A) so I shut the pi down.

Then, I found that the total current value gradually rose up from about 1A to 1.5A.

This seems to be so strange because when it gets shutdown, the power should be off as well,

and the pi only needs small amount of power just to light the red LED.  

I tried a few times but the result was always same...


I can't understand the reason why this happens, 

does anyone have ideas to explain this phenomena?


Thank you


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You'll find in general lots of SBC's have poor power management.

What should be happening is the CPU needs to send the RK808 PMIC the right power off commands before it enters it's halt state. That's probably  series of i2c commands and gpio1_a5.

If it keeps the power on, it may just be sitting there with the SoC fully powered up, wasting your power.


The board vendors don't seem to care much about the problem. If it powers up when you apply power, they think their job is done.

In theory there's nothing stopping these systems from entering sleep mode, like your phone or tablet does. They'll last weeks if you set them on airplane mode to disable the wireless and leave them alone.


The Raspberry Pi for example, uses almost as much power while "off" as it does then it's idle. The VideoCore CPU in it is fully awake waiting for you to turn it back on with a gpio.

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