The Raspberry Pi is a cheap, multi-purpose Linux computer great for education and maker projects. It is pretty bare-bones so if you are not careful you can end up with a rat's nest of cables just to turn it on and experiment. A solution that can turn the Pi into a compact laptop-style setup is to use a Motorola Lapdock, originally designed to dock with their line of Android phones. But why limit to a particular phone? A Lapdock is simply a nicely-packaged group of components available via USB and HDMI that you would end up connecting to your Pi separately anyway:
- Display (1366 x 768)
- USB hub
- Stereo speakers
- Portable battery pack
- Power supply
|Raspberry Pi with Lapdock in action|
Other portable Raspberry Pi solutions have also gotten a lot of coverage, such as this one and this one. They absolutely look like fun projects but at the end of the day I feel that my version is cheaper, cleaner, easier, faster to make, and more useful. I suppose my goal wasn't to make a fancy project but rather to make it easy to do other projects on the Pi without making a mess around the house.
|The completed setup|
Lapdock: I chose the Motorola Droid Bionic Lapdock because it was cheaper by chance than the also commonly used Atrix Lapdock. My understanding is that both are identical except for the orientation of the ports where the phone would connect. Other models of Lapdocks also exist and may have since been discontinued.
Cables: This took a lot of research. For the two cables, the required cable ends are
- USB A male to micro USB female
- HDMI male to micro HDMI female
|Assembled cables -- closer ends attach to Lapdock|
|Details of adapters -- close ends of adapters attach to Raspberry Pi|
Optional: I housed the Pi in one half of the Bud Industries shell case (which has two identical halves). Blue painter's tape attaches it simply (and robustly enough for around the house but not for travel) to the back of the Lapdock display. A USB wi-fi adapter makes the setup truly portable (and it's natively supported in the Raspbian OS).
Detailed parts info (on an old-timey HTML table!):
|USB Gender Changer, A Male To Male||$1.99||<5 days|
|USB 2.0 A female to Micro USB B female adapter cable FF||$2.49||7 days|
|30cm V1.4 Micro HDMI Male to Micro HDMI Female Cable for HTC EVO 4G Radar New (edit: this and this are available as of 8/8/13 and may work -- watch the length)||$8.39||4 days|
|HDMI Male to Micro HDMI Female Converter (Black)||$4.89||13 days|
|Motorola Droid Bionic Lapdock||$49.99||2 days|
|Edimax EW-7811Un 150 Mbps Wireless 11n Nano Size USB Adapter||$9.99||2 days|
Assuming you already have a Raspberry Pi, the total cost for this project is $67.75, or $77.74 with optional wifi adapter (includes taxes and shipping, at least most of it). Someone should tell this guy.
|Enough wires and flashing lights that my wife tells me I shouldn't use it on an airplane|
The Lapdock has no power button so it is only active when it sees something connected to the HDMI port, whether that items is on or off (more on that later). Hook up the USB cable and the Pi boots up right away. The Lapdock will power on whether open or closed. An odd behavior, presumably to signal to the Android phones to go in/out of webtop mode, is that the power to the USB port temporarily cuts out when the lid is opened or closed. This pause is enough to reboot the Pi, so unless you make some hardware kludges you'll just have to choose one way or the other before booting up.
Configuration: Very little needs to be done to complete the setup. The only thing I did was modify the Rasbian config.txt file to automatically send sound over HDMI (this is how to get to the Lapdock's speakers) using
Battery life: With the screen on and running the Pi, the battery lasts for several hours (maybe five but I never measured carefully). With the screen closed (and thus everything powered down on the Lapdock except for the micro USB port), one could run the Pi for a very long time. But why limit yourself to plugging in a Pi? You can plug in and charge any USB device as long as the HDMI cable is plugged into something or at least has its pins shorted to ground. I used this method to charge my iPhone 4S -- a fully-charged Lapdock took the iPhone battery from 15% to 69% which is a 54% increase.
Open issues and questions -- feedback welcome
- The Lapdock trackpad seems to have "tap to click" permanently enabled which is infuriating, to say the least. Does anyone know a way to disable it? This post indicates the issue is the firmware inside the Lapdock so a Raspian driver probably won't cut it, unfortunately.
- Is there another way to avoid the power interruption when opening/closing the lid besides another battery or supercapacitor? As long as we are hacking the firmware to turn off tap to click, may as well fix this.
- My thumb often touches the trackpad since it is so close to the buttons -- what type of material can I place along the bottom of the trackpad to make a dead zone? Electrical tape (even five layers) didn't work.