This guide will show you how to create a handheld Linux terminal, using a Raspberry Pi 2, a bunch of off the shelf parts and simple hand tools.
This is the second iteration of the terminal and has lots of new features, including a bigger touchscreen, double the battery capacity, accessible ethernet, and audio/video out.
There are also tweaks to how the keyboard works, as well as new multitasking stuff in the software.
- Raspberry Pi 2
- Adafruit PiTFT Plus 3.5inch touchscreen
- 3x USB sockets
- 2x laptop hard drive cases
- Lots of thin wire
- 3.5mm 4 pole audio/video jack
- 1x low profile ethernet socket
- Adafruit Powerboost 1000c
- Mini wireless keyboard
- Power switch
- Tactile momentary switch
- 5v to 3.3v step down convertor
- 1000mah Lipo battery
- Piano Hinge
Estimated Cost ~$120
- Soldering Iron
- Wire Strippers
- Craft Knife
- Hacksaw Blade
- Desolder Pump / Wick
- Helping Hands
- Drill/Rotary Tool (optional)
SOFTWARE HOW-TO GUDIE
I found a really great tiny keyboard that has full QWERTY keys, as well as all the special characters you need to use a text console.
It is also extremely usable in low-light situations, with its own built-in backlight.
Step 1. Go to the Adafruit site and download the custom Raspbian image for the 3.5 PiTFT, then follow the instructions for how to put it on the micro sd card
Step 2. Once you've got the screen booting, attach an ethernet cable and keyboard to the pi. We're going to install the i3 window manager. Open up a terminal window, type the following, then press enter:sudo apt-get install i3
Step 3. Now we can change the session manager. Type the following, press enter and change the option to Open Box.update-alternatives –config x-session-manager
That's it. Now when you use startx, you can right click to choose the i3 window manager.
HARDWARE HOW-TO GUIDE
Step 1. The first thing to do is remove some components from the Raspberry Pi board to make it as thin as possible. This includes:
- The 2x USB sockets
- Ethernet plug
- GPIO pins
- 2x camera connectors
- Composite Audio/Video jack
- HDMI port
Not everything is easy to desolder from the board, and I made good use of the mini hacksaw blade and cutters too. Just be careful not to damage components or scratch the board, and you'll be fine.
Step 2. Desolder the pins from the PiTFT board.
Step 3. Cut and prep some wires and create extensions for the USB, ethernet and audio/video ports.
Step 4. I modified the keyboard, allowing it to be powered by the Pi instead of it's own battery. I just added a 5v to 3.3v step down regulator to the battery contacts, and I also added a button that lets you toggle the backlight on and off.
Luckily, the 1000mah battery I wanted to use fits exactly in the same space.
Step 5. Now we need to prepare the case. Again, this is pretty straight forward, but takes quite a bit of time. I measured and cut the top and bottom halves of the case, mostly with the hacksaw blade, then finished it with plastic sheeting and vinyl tape.
I added the piano hinge at the back and drilled a few holes for the wires. I also glued on some rubber nubs to stop the screen overextending.
Step 6. To reduce the height of the powerboost, cut the top of the JST battery connector off. While you're at it, you can add a power switch to the Voltage, Enable and Ground pins, as well as the custom micro USB plug.
Step 7. Place everything in the case, and feed the wires between the bottom and top halves. Now you can solder everything together. I made sure the 2 battery wires went through different holes to minimize the risk of shorting if they break in the future.
Step 8. Close the case up, cross your fingers and power the computer on.
You now have a handheld Linux terminal fits in your back pocket. The i3 window manager, coupled with the touchscreen really helps free up space for multitasking, and it can be transformed easily into a full Linux desktop when plugged into an external monitor.