wifi adapter (product 814) fails when hdmi output is connect

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scotthz
 
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wifi adapter (product 814) fails when hdmi output is connect

Post by scotthz »

I have been using the mini wifi adapter (product id 814) reliably for quite a while with Occidentalis 0.2. No problems to speak of, regardless of whether I put the full config in /etc/network/interfaces or use the indirect method involving wpa_supplicant. Both methods work fine, until I connect a monitor via HDMI cable to my Raspberry Pi. With HDMI connected, the wlan interface never gets an IP address (I see the sequence of "DHCPDISCOVER on wlan0..." messages, then finally "No DHCPOFFERS received".

This only occurs when HDMI is connected. I believe that I have ruled out power as the problem.

Any suggestions or advice?

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adafruit_support_rick
 
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Re: wifi adapter (product 814) fails when hdmi output is con

Post by adafruit_support_rick »

This is almost certainly a power problem. The power budget for USB is marginal for WiFi adapters. turning on the HDMI hardware (which is what happens when you plug in a cable) is sapping that supply even lower.

What kind of power adapter are you using? How many mA?

Do you have a self-powered USB hub? Try connecting the WiFi through that, and see if the problem goes away.

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scotthz
 
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Re: wifi adapter (product 814) fails when hdmi output is con

Post by scotthz »

I am using a 2A (2000 mA) self-powered hub. I have tried connecting the wifi adapter through that as well as directly to the Pi. Same result.

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Re: wifi adapter (product 814) fails when hdmi output is con

Post by scotthz »

To add to the preceding: I am using a macally 7-port powered USB hub with 2A supply.
I am now wondering if there is something weird in the way power is budgeted across the different USB connections, because in trying a couple different permutations, I have found one that works, in that the wifi adapter is now working okay, even with connected HDMI. This didn't work before, even with a different 2A supply.

So, thanks for pointing me again to power being the culprit. I really thought I'd ruled that out.

Scott

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Re: wifi adapter (product 814) fails when hdmi output is con

Post by adafruit_support_rick »

Hubs do some funny things.

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