The Gray Screen of Despair

The easiest way to connect to a computer running Linux remotely from a Windows machine is to use xrdp.   It works flawlessly to connect to a PC running Ubuntu 12.04 LTS.  However, after upgrading to a newer distribution, an xsession bug appears, resulting in a blank Gray Screen of Despair after attempting to log in remotely.   After scouring the Internet, I found an easy solution, replace gnome with xfce4.   Follow these easy instructions to eradicate the Grey Screen of Despair from your life.

GAPfiller GSM900 Design Files Released!

The hardware design files for the GAPfiller GSM900 have been released on  Github

  • Includes: OrCAD schematics, PADS PCB layout, Gerber files.
  • Coming soon: USRP FPGA firmware modifications, USRP Hardware Driver (UHD) and OpenBTS Transceiver modules for GAPfiller GSM900, technical documentation

The GAPfiller GSM900 is open-source hardware, released under the CERN Open Hardware License version 1.2.

January 2014 Update


Close-Haul Communications, Inc. is an open source wireless hardware company founded in 2009 by Robin Coxe and Tux the Polyester Penguin. Our tagline, Closing Gaps, Opening Access, captures our intention to design and build affordable, open wireless infrastructure hardware that enables people to create cellular networks outside the walled gardens of telecom monopolies. Close-Haul Communications is a charter member of the Open Source Hardware Association. Our first design, the GAPfiller GSM900, is intended as a prototyping platform for OpenBTS research and has been optimized for the GSM 900 band (GAP= GSM Access Point). The GAPfiller GSM900 is a mezzanine card compatible with the Ettus Research USRP series of software defined radio baseboards. Although not yet released commercially, the GAPfiller GSM900 board is open-source hardware covered under the CERN Open Hardware License, version 1.2.

The design files (OrCAD schematics, PADS PCB layout, Gerber files, and supporting documentation) were uploaded to Github on 7 January 2014. FPGA firmware and Linux driver modifications will be necessary to run OpenBTS or osmo-trx on the GAPfiller900. Stay tuned for more details.


No Ethernet! Help!


Hopefully, one or both of these factoids will save you several hours of Googling and general frustration if attempting similar DIY IT upgrades and the Ethernet connection goes kaput.

Virtual Box Networking Fail


I recently installed Virtual Box on both my Windows 7 laptop and my MacBook Air in order to run Ubuntu as a virtual machine.  I downloaded the latest versions of Virtual Box and Virtual Box extensions, as well as the Ubuntu 13.10 x64 ISO image and completed the relatively painless installation procedure.   After restarting the VM and logging in, I discovered, much to my chagrin, that Ubuntu couldn’t access the Internet.   The easy solution:

Log in to Ubuntu and open a terminal.
$ cd /etc/network
$ sudo gedit interfaces (enter your password when prompted)

Add the following 2 lines to the interfaces files:

auto eth0
iface eth0 inet dhcp

Save the file.

$ sudo ifdown eth0
$ sudo ifup eth0

Problem solved!

Apple AirPort Time Capsule Meets Comcast Cable Modem.  MAC address Mayhem Ensues.


Yesterday, I decided to upgrade my ancient WiFi router.   Thinking I could kill two birds with one stone, I bought an Apple Airport Time Capsule and picked it up on the way home from work at the local Apple Store.   Way back in prehistory, my laptop at the time had been directly connected to the cable modem.  Comcast associates a single MAC address with the cable modem (for no particularly good reason other than to charge customers more to rent a cable modem with an integrated router).   I own my cable modem.  When I subsequently added the aforementioned WiFi router, I got around connection problems by spoofing the MAC address of the laptop using the Netgear router configuration web app.   Pretty much all routers known to man have this feature.   Except, of course, Apple AirPort routers.   Apple earns well-deserved accolades for industrial design, but sometimes these industry-standard, yet mysteriously lacking features made me shake my fists and fume with rage.  What gives Apple?!?

Thankfully, the solution in this case is relatively low-tech, but does involve some patience:  1) Unplug the cable modem.  2) Unplug the AirPort Time Capsule.  3) Disconnect the coaxial cable from the cable modem.  4) Disconnect everything except the WAN Ethernet cable from the AirPort.  5) Wait 15-30 minutes.  Yes, suffer in silence without broadband Internet for a half an hour.   6) Reconnect the coaxial cable to the cable modem.  7) Connect the AirPort WAN Ethernet cable to the cable modem.  8) Power on the AirPort FIRST.  9) Power on the cable modem.  10) Wait until all of the link lights on the cable modem are blinking, probably green or blue.  11) Attach a Mac to the AirPort using an Ethernet cable.   12)  Open the AirPort Utility on the Mac and click on the AirPort Icon.    Release the DHCP address.   13) Wait a few seconds to allow the cable modem to identify and fully grok the Ethernet WAN MAC address of the AirPort.  14)  Pat yourself on the back when the Internet works.