When I built my original Raspberry Pi Tablet (aka the “PiPad”), one of the hardest (and most expensive) things to source was a Pi compatible touchscreen that could run on 5V. As far as I know, there is only one supplier and from according to many makers who are trying to build a PiPad. They are frequently out of stock.
Of course, this is all about to change with the newly released Raspberry Pi Touchscreen. At an announced $60 price, the screen is under half the price (and a fraction of the shipping costs) than other versions on the market. Additionally, since the screen is an official Raspberry Pi product, it will be completely supported by the Raspbian operating system and support is likely to be integrated into others (OSMC, Arch, etc.)
The 7” screen features capacitive touch and connects to all versions of the Raspberry Pi using the DSI interface (although older boards won’t fit the display’s mounting holes.) The included adapter board routes the touch inputs through the DSI port which is very nice because it doesn’t take up any of the 4 USB ports. Additionally, the adapter board offers flexible power options; it can share power with the Pi using a MicroUSB cable or jumper wires from the GPIO port, or you can power it independently of the Pi (if that’s your thing.)
Assembling the screen / mounting the Pi requires only a small Philips screwdriver and takes just a few minutes. Be sure to pay close attention if using the GPIO for power. Doing this incorrectly can damage the Pi.
If you assemble the display using the instructions, the resulting solution is, well, not elegant - especially if you’re planning to build an enclosure. Because the adapter is uses the same footprint as a HAT, we decided to flip the entire Pi over for a lower profile mounting solution. This method successfully reduces the height by 1/2 provided you 1) don’t mind bending a few of your Pi’s GPIO pins out and 2) don’t mind if the DSI ribbon cable gets a bit scrunched up.
To verify that everything works, we’ll need to flash an SD card with the latest version of Raspbian Wheezy, hook it up to the Internet via Ethernet (or use WiFi but that’s easiest done by connecting a USB mouse, booting into Raspbian, and using the GUI tool to set it up.)
Once connected, power on your Pi, boot it up, log in (user = pi, password = raspberry) and type “sudo apt-get update upgrade” into prompt. Type “y” when asked if you’re sure you want to do the update. If you booted in the desktop, open up the terminal and type the above command. After the upgrade is complete, reboot your Pi, log back in, type “startx” to load the GUI, and your touchscreen should be working! If it isn’t, try rebooting.
To get the display to boot into the operating system without logging in, type “sudo raspi-config” into the prompt, select option 3, and select “Desktop Log in as user ‘pi’ at the graphical desktop”. Click finish then reboot. Your Pi and it should load automatically into the desktop environment.
With the profile lowered to a reasonable amount we can start designing an enclosure. The original PiPad with it’s 10” screen used CNC cut baltic birch plywood. Since most folks don’t have access to a CNC machine (and since the 7” screen is smaller) I decided to design the enclosure to be 3D printable. Currently there are no mechanical drawings of the screen available so I simply laid the screen on a flatbed scanner and imported the image into AutoDesk Fusion 360 for tracing and built up from there.
I must emphasize that this enclosure is far from a perfect solution, mainly because we haven’t yet sourced a battery. In the current version, we found a battery that happens to fit, not one that the case was designed around. Once the battery is sourced I’ll create something less tray-like with external ports and such. For now, this one is a proof of concept. From the testing we’ve done so far, the Pi 2 + Touchscreen + WiFi adapter consumes about 1000ma/hr. I’d like to get 6 to 8 hrs of battery life so we’re looking for a battery with the following features:
After finding an appropriate right-angle usb cable, the entire assembly was fitted into the case. The last piece of the puzzle is installing an onscreen keyboard. I installed matchbox keyboard on the original PiPad and once again on this version. To install (assuming you’re still connected to the internet), open terminal and type “sudo install matchbox-keyboard”. Type ‘y’ when prompted then reboot your pi. Upon reboot the keyboard will be available under Menu -> Accessories -> Keyboard.
The result is a self-contained and fully functional Raspberry Pi based tablet that serves for the foundation of the “PiPad 2.0.” If you’d like to print the files yourself, the STL and Fusion 360 files are available on MCM Electronics' GitHub account or directly from Autodesk 360. Feel free to give it a try and stay tuned for the next version and other projects.