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I'm experiencing issues with a couple Raspberrys.

When setting up the boards, I plug them to HDMI monitor, keyboard and mouse. (no ethernet). I configure it to use wifi network and store that in the wpa_supplicant file. Rebooting the device works fine, and it always instantly connects to the wifi.

When running them headless (which is the objective), ie, no keyboard, no mouse, no hdmi (no ethernet !), the devices fail to connect to the wifi, or very randomly do.

Is there something I'm missing ?

Could the HDMI connection be a reason for the wifi behaving differently ?

More information: I've tried this with Raspbian Wheezy and Jessie. And both have same behavior. Currently it's running off of Jessie. (Found on Raspberry website).

Regarding setup.

  • Flashed the SD card.

  • Boots directly to desktop mode (with keyboard/mouse/hdmi plugged in).

  • We use Adafruit Wifi USB modules (ie. the realtek ones).

  • Once booted, we simply use the wifi connect pannel tool. Connect to our internal wifi.

  • That wifi ssid/psk gets stored into /etc/wpa_supplicant/wpa_supplicant.conf file.

We reboot (leaving everything plugged in), wifi connects almost instantly to our network everytime. (we can monitor this from our computers with lan scanning tools).

If we then reboot, and unplug everything EXCEPT power plug and Wifi module (ie. HDMI disconnected, No keyboard, No mouse). Then we monitor our lan, and the devices are randomly failing to connect.

Thus my question: Is there a chance that the configuration of the PI has an effect as to it's operation from a power standpoint, os standpoint, usb standpoint when cables are plugged in or not ?

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  • Without knowing what you did no one can help. List your changes. You also need to specify what distribution you are using. Is there any reason you didn't use the recommended GUI setup?
    – Milliways
    Commented Nov 19, 2015 at 3:27
  • Are you changing anything else about the setup? USB hubs, location, power supply, etc?
    – Jacobm001
    Commented Nov 19, 2015 at 3:27
  • Will edit my post to reflect your questions. But there is no significant changes.
    – teuteuguy
    Commented Nov 19, 2015 at 3:43
  • To add on this, I ask because we've tried Ubuntu Mate distribution also, and discovered that when using the default config.txt file included, the pi does not boot, because our monitors (HDMI) resolutions differ from the included configuration file. When using the Raspbian config.txt on the Ubutnu Mate distro, the devices boot fine on our monitors. So it seems that config.txt can have some impact relative to HDMI.
    – teuteuguy
    Commented Nov 19, 2015 at 3:51

2 Answers 2

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Does your /etc/network/interfaces file have auto wlan0. If not please try adding this line above your wpa-supplicant

Also I support the use of higher current Power Adapters to drive the WiFi USB adapters. I use Current Ratings of the following:

Input: 100-240 V ~ 50/60 Hz 0.3A Output: 5 V - 2.1A / 5.2 V - 2.1A

Ones from Goobay work well for me.

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I am no expert in this area , but I believe that the HDMI cable is working as an antenna. I am mentioning this because my old desktop PC had same problem it had an internal WiFi card but it couldn't connect to the home wireless network so I had an extra USB cable lying around which was not used to connected to any other device but just connected to the desktop so that it acts as an antenna for WiFi

I don't know much about Raspberry Pi but I think that because Mob body and lesser components of metal maybe there is a lack of an antenna, its not that it doesn't have one but it may not be efficient

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