Trying to get Edimax EW-7811UN wifi dongle working, but Pi reboots upon plugging it in

Question

I'm trying to get an Edimax EW-7811UN wifi dongle working with the 2012-08-16-wheezy-raspbian image. The straightforward way to do this seems to be to download and run MrEngman's script. In trying to do this, I've plugged in the dongle when prompted by the script, and the Pi immediately crashed and rebooted.

This happens each and every time I plug in the dongle after booting the Pi. When booting with the dongle plugged in, the Pi boots after throwing lots of udev warnings and hanging for a long time, and it's listed as should be in lsusb as a Realtek 8188CUS based device; but that way, the script will not work (incorrectly prompts that the device doesn't support scanning).

I'm running the Pi on an HTC phone charger with a 1A power output. This happens regardless of whether I also have a USB keyboard plugged in on the other USB port, or not (i.e. the dongle is the only USB device). If it's a power draw problem, I find that strange, since lots of people seem to be reporting that this is a very low power dongle and that they are running it with no need for a powered USB hub, even with lower output power sources...

This seems to be such a popular device with Pi users, but I'm having no luck with it. Any help is appreciated.

Answer 1

I have a very similar setup using this same dongle with Raspbian and am powering my Raspberry Pi with a HTC phone charger as well. I had a lot of trouble for a while with the RPi locking up or crashing, as well as the long line of udev warnings that you mention. It didn't seem to matter whether I had it plugged directly into the RPi or using an independently-powered USB hub; however, it eventually started working okay after a recent kernel/firmware update. I also had returned the RPi to its default CPU speed (I was previously overclocking it). I would suggest using rpi-update to make sure you have the latest kernel and firmware, and possibly try disabling any overclocking if you are doing that.

My current setup, which is working for me, has the WiFi dongle plugged directly into the RPi, with my keyboard connected via the powered USB hub.

Edit: After writing this answer, I re-enabled overclocking on my RPi to test that theory. It still seems to be running fine, so I don't believe that was actually the problem before. Also, it seems worth nothing that the latest kernel (as of 2012-09-03) now includes the driver required for this by default.

Answer 2

I have the exact wifi adapter. All you need to do is NOT plug in the adapter straight to the pi but through a powered usb hub (maybe 20$ at office max, wal-mart, etc.). Works for me this way.

Answer 3

I'm running the Pi on an HTC phone charger with a 1A power output.

I have trouble with the mains2usb charger of my late blackberry.
Problem is: the charger can output 1A to get the LiPo battery charged, but it doesn't need to sustain 5V, since the battery is likely around 3.8V. So there's a voltage drop under charge (because it's cheaper, whatever the phone manufacturer). I'm getting 4.9V without ethernet, and 4.75V with ethernet wired, which basically means anything I want to plug in goes through a powered hub.

Get a voltmeter on testpoints 1 & 2 with and without your dongle.