Friday, January 18, 2013

Resolving Raspberry Pi USB power problems

With only 120mW per USB port, the Raspberry Pi is woefully inadequate for most USB items, and almost inpossible to use with an unpowered Hub.

I traced the incoming +5v from the mini-usb power plug and found that the outside of the polyfuses for power are directly connected, making it pretty easy to solder some extra wiring to power the ports:


Was able to run a 4 port unpowered hub (off a 1500mW Power input) with the following:


  • 200mW USB 802.11n Wi-Fi Dongle
  • Linksys Class1 bluetooth adapter
  • Neotel Zyxel 3G/HSPA USB adapter
  • USB 100Mbps RJ45 Network Adapter
as well as a USB keyboard.

No problems whatsoever and unplugging/replugging devices off the hub as well as the keyboard did not force the unit to reset.

I also added a nifty Heatsink to the CPU/Ram BGA with some sticky thermal tape - made 1Ghz on the CPU finally possible and stable.


2 comments:

  1. hi, i have the rev 2 pi board. i don't want to use any other device plugged into the usb ports on it but my usb wifi dongle. http://www.amazon.com/gp/product/B005CLMJLU/ref=oh_details_o05_s00_i00
    i noticed that when this is plugged in and i am viewing certain addon's the raspberry pi reboots. i was to to get a usb hub or short out the polyfuse. if i short out the polyfuse would that fix the reboot issue when the wifi dongle is plugged in.

    thanks!

    ReplyDelete
    Replies
    1. No. If it was a polyfuse issue, the pi would take some time to return to working state, not just reboot. What you describe sounds more like a marginal power issue, when the supply isn't quite up to the load - a common issue. An ordinary multimeter isn't up to the task of detecting voltage droop, so the way to find out is to just try another supply and see if it is stable.

      Delete