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When running X and when it's not content that it can draw enough power from the adapter, my RPi displays an RGB colour square on the screen. (At least, I THINK that's what the RGB colour square indicates.)

How does it sense that there's not enough juice available?

It doesn't die or reboot: it seems to be able to sense when there's not enough current available. Is it sensing a voltage drop in the supply, for example?

KDM
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1 Answers1

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The Pi (at least all since B+) has a power monitor - the APX803 chip triggers if voltage falls below 4.63±0.07V. This drives the power LED and is connected to a pin on the chip.

In fact the Pi will run at lower voltages as it requires 3.3V and has an on-board regulator. The lower voltage may impact peripherals.

Milliways
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