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My Raspberry Pi2 is freezing. Some online forums mentioned that freezing is due to inefficient power supply (as minimum allowed voltage is 4.75 v). In order to test this, I want to have a running job that is able to report voltage input of the power supply. Can anyone advise how to have a script that can report power level of the supply.

  • Read the power level (voltage) from what? The Pi does not provide any information on the state of the 5V supply line (other than good/bad). – joan Apr 12 '16 at 8:01
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The Pi cannot do this, as it has no analog capability. You could of course add suitable hardware.

The Pi (at least all since B+) does have 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 (35 for B+ but it may have changed for P2) which could be monitored.

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.

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Pi randomly freezing, probably due to insufficient power or an unstable power source.

My recommendation is at a minimum to use a high quality phone or tablet charger that can reliably output 1.2A at 5V. However, I strongly recommend using an official Raspberry Pi power supply.

In terms of measuring power consumption a multimeter is your best bet, although this website might interest you.

As stated on the website run this set of instructions in the LXTerminal.

git clone https://github.com/raspitv/pi2test/

cd pi2test

python Pi2test.py 

This will give you a program that should measure the current draw of your CPU.

However looking at the results, the most the Pi 2's CPU consumes is 420mA with all 4 cores under load. Once you account for USB devices, and other circuitry on the Pi, you can see where the 1.2A recommendation comes from.

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