MicroSD power consumption on Expansion Board, PyTrack, PySense, etc


  • Pybytes Beta

    Following @jmarcelino comment from another topic :
    Power Consumption Issue

    The SD card is always consuming power even when idle (during deepsleep) about 5mA. For low power applications using the SD card is not recommended.

    I want to confirm about the 5 mA consumption when using microSD card :

    • this happens on all Pycom boards with microSD ? Expansion Board v1/v2/v3, PyTrack, PySense, etc ?
    • this happens even before mounting microSD card in MicroPython ? Or only after mounting ?

    The Pycom community would gain a lot if we do detailed power consumption analysis of microSD usage, e. g., in active mode x deep sleep mode, microSD inserted x not inserted, before x after mounting, before x after openning file, during reading x writing to file, etc.

    Many of us want to use deep sleep to obtain long battery endurance, counting each uA, so this microSD 5 mA issue is important.


  • Pybytes Beta

    @jmarcelino
    Thanks ! So for each uSD card we need to test the power usage, both in active mode and deep sleep mode.



  • @rcolistete
    This depends on the microSD card/sd card controller used, as you noticed the higher density newer technology tend to have lower power consumption. Also there are differences regarding the unused (floating) pins.


  • Pybytes Beta

    First tests with Expansion Board v2.1 with respect deep sleep with/without uSD card.

    1. alone (without LoPy/WiPy/etc), consumes about 0.12 mA (battery connector with 3.3V) to 0.18 mA (with 5.0V), with or without uSD card, with any jumpers configuration;

    2. with LoPy4, without uSD card, with battery connector with :

    • 3.3V : doesn't boot;
    • 4.1V from Li-Po/Li-Ion battery, only TX/RX jumpers : 0.16-0.17 mA;
    • 4.1V from Li-Po/Li-Ion battery, with all jumpers : 0.23 mA;
    • 5.0V from power source, only TX/RX jumpers : 0.19 mA;
    • 5.0V from power source, with all jumpers : 0.25 mA;
    1. with LoPy4, with 8GB Sandisk UHS-I uSD card (not mounted, without open files, just inserted), with battery connector with :
    • 3.3V : doesn't boot;
    • 4.1V from Li-Po/Li-Ion battery, only TX/RX jumpers : 0.40 mA;
    • 5.0V from power source, only TX/RX jumpers : 0.40 mA;
    1. with LoPy4, with 32GB Samsung Evo UHS-I uSD card (not mounted, without open files, just inserted),, with battery connector with :
    • 3.3V : doesn't boot;
    • 4.1V from Li-Po/Li-Ion battery, only TX/RX jumpers : 0.30 mA;
    • 5.0V from power source, only TX/RX jumpers : 0.31 mA;

    Conclusions to save power during deep sleep with Expansion Board :

    • it is important to use only TX/RX jumpers, or else we will have extra 0.06 mA;
    • large voltage values implies some extra (e.g., 0.02) mA;
    • avoid using uSD cards, because even just inserting a uSD card, not mounted, without open files before deep sleeping, there is an increase in deep sleep current, depending on the type of uSD, e. g., extra 0.21-0.24 mA for a 8GB uSD, extra 0.12-0.14 mA for a 32GB uSD.

    But the cited extra 5 mA due to uSD card being inserted wasn't obtained, even during active state.


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