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I am working with some "low power" applications in which a 3.3V micro controller with some electronics around it logs some information for 20 minutes, and then the information needs to be processed. The processing step is too expensive for a micro-controller to perform, so I need a micro computer that does these calculations once in a while. I do not need USB, nor HDMI, nor ethernet etc, from the micro computer. All I need is 1) the ability to talk to the micro controller through I2C / SPI 2) the ability to work with a 3.3V input 3) the ability to run a command-line only Raspbian OS or something like that, so that I can run some Python scripts.

Any idea what kind of hardware I can use for that? Is a RPi suited? I think this is somehow related to Can I power Raspberry Pi (newer models) from 3.3v Supply Alone? , but I am a bit unsure of what the conclusion is. Should I rather use another RPi-similar micro computer? If yes, what would you suggest?

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    Pi needs 5V - not suitable for your needs – Jaromanda X Aug 24 '20 at 10:16
  • Well, at least some of the older boards work with pure 3.3V according to the link? – Zorglub29 Aug 24 '20 at 11:06
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If you need to run Python on a low-power system, see if pyboard, teensy or a similar Cortex-based microcontroller board is enough for both data acquisition and processing. You will never reach the power levels of such boards if you include a Pi (or a different SBC) in your system.

I'm pretty sure you won't be able to power newer Pi boards (Pi 3/ Pi 4) with only 3.3V without modifications: they won't boot with such a low voltage. The only Pi that seems to be able to work with 3.3V (by shorting 3.3 and 5V pins together) is the original Pi model A which uses linear regulators for internal power distribution (and, more obviously, a full-size SD card).

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  • Mmmh, I think a teensy and likes will be too weak for what I want to do. I do not want to do some pycircuit, I want to be able to fully use numpy, scipy, etc... – Zorglub29 Aug 24 '20 at 11:06
  • You could try the Microbit but most micro controllers are not designed for heavy computational tasks (hence the 'controller' bit) - use the controller to collect the data and the Pi to process it. You can always wake the Pi up from the Microcontroller to process the data or put both to sleep and use a real-time clock to wake the controller first (to get data and wake the Pi) - that will cut processing down. Also - why not use a Pi in the cloud to process your data and save the power for the controller and WiFi or LORA? – user115418 Aug 24 '20 at 16:25
  • @Zorglub29 For a battery-powered application, I would invest some time in finding C/Fortran versions of the numpy libraries you need (LAPACK?), which would let you run your calculations on a much smaller CPU core and use much less computational and electrical power. – Dmitry Grigoryev Aug 25 '20 at 10:44
  • Yes, of course that is an option, but it is quite some work to do. I am interested in "relatively low" power, but not at the cost of difficulty to program / set up. For example, this kind of applications: arxiv.org/pdf/1901.02410.pdf . "low power" is needed, but not talking about being super effective either when the electronics is first switched on 20 minutes each 5 hours... – Zorglub29 Aug 25 '20 at 10:48
  • @Zorglub29 You have your answer then. Raspberry Pi needs 5V to run properly, and AFAIK modern OS will refuse to boot at voltages below 4.75V. You'll need a different board. – Dmitry Grigoryev Aug 25 '20 at 15:09

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