What should the minimum current rating of a power supply be for LoPy4?



  • I can't find this number in the specs.

    Occasionally when plugging into my mac (usb port: 500 mA rating), the big LED on pycom goes solid green or white and stays that way.

    However if I plug into a fairly hefty USB battery instead, it always behaves as expected, no mysterious LED illumination.

    My theory is that my USB power supply in my Mac is unable to provide the kind of peak current required when the pycom starts up.



  • @dws

    There isnt at present, but ill add it to the to-do list!



  • @seb Thanks! This is pretty interesting to me since I would assume there are a lot of people that either don't know, or forget, that a laptop (or wall wart) usb supply could be insufficient. Is there a caveat anywhere in the docs that advises people to know what their usb current sourcing is and to beware of some supplies?



  • If you check the Vin label on the OEM module pin out diagram, it gives some suggestions as to the required currents:

    W01/WiPy = 450mA
    L01/L04/LoPy/LoPy4 = 650mA
    G01/GPy/FiPy = 950mA



  • @dws note that on some MacBooks, all USB ports do not necessarily behave the same. I know on mine I have seen issues resolved simply by switching a device from the left to the right port. Can’t remember what device that was though, don’t believe it was a LoPy.



  • @dws simply adding the wort case power consumption of the components gets to about 400 mA (ESP32 and SX1276 transmitting with max power at the same time, RGB LED on at max brightness). But that is not likely to happen at boot time.
    My question about your test set-up is:

    • do you use the same USB cable for both tests?
    • when connected to the MAC and kind of frozen, does the device start when you push the reset button?

 

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