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Hoping someone could help verify something for me.

Up until a few days ago, my Edimax EW-7811UN was happily buzzing along. I was playing around with the GPIO pins when suddenly I noticed the blue light inside the dongle stop flashing.

Thinking that I had possibly shorted out the Pi and it had reset, I waited for boot and for the light to begin flashing again, but it didn't.

I then tried the device using another SD card, different OS, in the same Pi. Running lsusb, I could not see the device listed. I then tried 2 other Pi's, each with different OS's to no avail. Nothing listed under lsusb.

The strange thing is that if I plug the dongle into my laptop, Windows 8 detects and installs it, I can connect to my wireless network and browse the internet.

Is it possible it may be fried somehow, and the Pi can't supply enough volts to it, where the laptop can?

Any help appreciated.

thekman31
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2 Answers2

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I had this problem and putting "dwc_otg.speed=1" in my /boot/cmdline.txt fixed it. What that does is make the Pi treat the Edimax as a USB 1.1 device (rather than the 2.0 device it is). That cuts your theoretical throughput from 480 Mbps to 12, but even 12 is likely more than your Wifi access point will supply anyway.

Unfortunately, sometimes even this doesn't do it. In that case, I boot up the Pi without the Edimax, and then I insert the Edimax after the Pi is up. I have no idea why hotplug would be more reliable than coldplug. But in any event, before the dwc_otg.speed=1 thing, the success rate was zero percent.

Ghanima
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Theodore Sternberg
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I've come to believe the Edimax 7811un really does have some problems. I deployed dozens of Pi systems as door access controllers and most of them use the Edimax dongle for WiFi. In my application they only connect to the network for a few moments once a day to exchange information with a host. In the last few months, the automated scripts that use "iwconfig" and "dhclient" commands to grab (and then drop) a lease will sometimes fail, saying that wlan0 does not exist. Soft rebooting (from the console) does not bring them back. Power cycling does, but anymore, I've found I can just unplug them from the Pi and plug them back in: the blue light flashes, and everything is happy. It is not at all predictable, and on the older Pi systems I used in most of the installations, there's no way in software to power cycle the USB ports. Newer installations use Pis with built-in networking. Since a lot of the systems started having this happen at the same time, I am thinking there may be a heat-related degradation of reliability over time due to under-design.

stringman
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