Ben's notes

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)

https://projects.drogon.net/testing-setting-the-usb-current-limiter-on-the-raspberry-pi-b/

• Update to latest firmware:

  sudo rpi-update

• Edit /boot/config.txt

  max_usb_current=1

• 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

OR

• Install WiringPi: http://wiringpi.com/download-and-install/
• 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
  1