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I use a freshly installed Volumio (based on Debian) instance on a Raspberry Pi 2 Model B Rev 1.1 equipped with an Edimax EW-7811Un USB device to get WiFi. Power is supplied from a HifiBerry AMP+ sound card fitted onto the Pi. The WiFi signal is very strong.

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But when I cold boot my Pi (meaning the Pi has been turned off for hours) WiFi doesn't work. The Edimax device blinks blue on and off with a steady rhythm. While such blinking usually constitute an error indication, the documentation fails to mention it. If I also use Ethernet cable and run lsusb I see that the Pi does recognize the USB device correctly, yet it's not working.

I pull the power from the Pi, wait 5 seconds, and then turn it on again. Then WiFi works!

The problem can be replicated if the Pi gets enough time to cool off. What does this suggest? Hardware problem with the dongle, or the Pi? Is there something I can do with software to attack the problem?

  • I have the same adapter and it causes a lot of trouble to me too. Sometimes I have to unplug it from the USB then put it back on and it works (without rebooting the whole system). I solved the problem by not using it, and using a different adapter. But if there is a solution, I'd be happy to hear it. – Radu Jan 19 '18 at 9:30
  • @Radu: Yes, I've found reports on the net that Edimax dongles are unreliable. So I find it strange that the device seems to be so popular, which is why I purchased it. I guess buying a RPi3 with in-built wifi is the easiest solution :( – Gruber Jan 19 '18 at 9:36
  • They are popular because they are small, cheap, and on Windows they work decently well. I am using this adapter and it works well for raspi: amazon.com/Panda-Mini-150Mbps-Wireless-Adapter/dp/B003283M6Q/… – Radu Jan 19 '18 at 9:43
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Hmmm, I'd guess that both the HiFiBerry and the WiFi dongle together draw too much power. You should first try cold booting with the WiFi adapter alone, then the HiFi. Because the HiFi connects via pins, the Pi's likely to default to give all the power to it over USB. A stronger 5v wall adapter should help in this case. I'd guess it works when not cold booted because once the Pi recognizes the device, it adjusts the kernel accordingly to supply power equally. If this doesn't workout; try a new OS.

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