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Raspberry Pi B+ USB current

You can change the RPI USB current limit. Keep in mind that the PSU also is able to deliver the current, e.g. 2Amp.

All that max_usb_current=1 does is to set GPIO38 high, which in turn turns on a FET, which connects a second 39K resistor in parallel to an existing one, on pin 5 of U13, the AP2553W6 USB power manager, lifting the current limit from 0.6A to double that (1.2A)

  • Update to latest firmware:
    sudo rpi-update
  • Edit /boot/config.txt
  • Reboot


  • Check gpio38, value should be '1'
    sudo bash
    cd  /sys/class/gpio
    echo 38 > /sys/class/gpio/export
    cat /sys/class/gpio/gpio38/value


  • Check:
    # gpio -v
    gpio version: 2.20
    Copyright (c) 2012-2014 Gordon Henderson
    This is free software with ABSOLUTELY NO WARRANTY.
    For details type: gpio -warranty
    Raspberry Pi Details:
      Type: Model B+, Revision: 1.2, Memory: 512MB, Maker: Sony
  • Check values, GPIO 38 should be '1':
    # gpio -g read 38
raspberrypi_usb_current.txt · Last modified: 2021/10/09 15:14 by