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Using Arduino, I'm trying to detect whether Raspberry Pi has successfully turned itself off. I first tried to check on the pins that are used for serial communication between said devices but the pin state is obfuscated by voltage level shifter that protects Rasperry Pi from (eventually accidental) 5V voltage.

So my plan is to set any other Raspberry pin HIGH and hope it will go low as soon as the Arduino shuts itself down.

But I have doubts whether the pin will not lose its state sooner (as soon as my controller application exits, or during the shutdown phase).

So is pin approach a good one if I want to check if the Rasperry Pi is off?

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  • \$\begingroup\$ Why not get the Pi to output pulses when it is active. Lack of pulses means it has shutdown. \$\endgroup\$
    – Andy aka
    Jun 27 '13 at 22:54
  • \$\begingroup\$ How about monitoring the supply current to the Pi. \$\endgroup\$ Jun 28 '13 at 9:45
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Setting a GPIO pin to a high voltage level is one option. Whether the device is off or set to low, the Arduino can detect such a "voltage". Pins aren't going to float high when the Pi is powered off.

Keep in mind that the the PI is a 3.3V device. That's VERY close to the high/low threshold of an Arduino, which uses 5V I/O. You might consider using one of the Arduino's analog inputs to detect the state of your Pi.

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