Recently, I came across a barely used Motorola Laptock being sold for 10€. Having no idea what a lapdock was, I did some exploring and found out that it was designed to be an external monitor, keyboard, battery touch pad, speakers and a USB hub to a specific Motorola Atrix 4g smartphone that came out in 2011.
It is basically a peripheral device. The phone was the brains of the system. In other words, you would plug the phone into this dock, the dock would power on if it detected HDMI, and the whole thing acted like a laptop.
- HDMI cable for Video and Audio
- Micro-USB to power the Pi from the Lapdock battery and to use the touchpad and keyboard.
I bought it right away, with the idea to repurpose it as a portable battery powered Kodi media center.
The build quality of this lapdock is amazing. I didn't want to damage it in any way, so instead, I 3D printed a case which allows the Pi to be plugged into the Lapdock just like the phone, and appropriately named the whole thing πtrix in honor of the original Atrix Motorola phone.
Step 1: Parts and Tools
- Motorola ATRIX 4G Lapdock
- Raspberry Pi Zero W
- MicroSD card, 8GB or more
- Type D Micro HDMI V1.4 Socket Female To Type C Mini HDMI Male Adapter Cable HM - ebay
- Micro USB Male To Female Extension Cable - ebay
- 3mm Wood screws - 6 pieces
- 3D Printer
- Retractable utility knife
- Sandpaper - 120P for rough 3D sanding, 320P and 1000P for extra fine finish
- Needle nose pliers
- Phillips screwdriver
- Small file set
- Matte black spray paint
- Nail polish
Modeling compound, like Play-Doh or Clay
Step 2: Printing the Pi Enclosure
The case design is simple, consisting of a main bottom part and a lid.
The bottom part houses the Pi, and has an opening which aligns with the HDMI and USB ports on the laptock. It was printed using PLA on a DIY Prusa i3 MK2 clone. For me the print turned out badly, especially the case lid. I considered redoing it, but decided to try and fix it.
Step 3: Post Processing the Enclosure
Once the print is done, remove the supports using needle nose pliers or any other tool you see fit.
Start sanding with rougher sand paper, and progress to finer grit to get the finish as smooth as possible.
Use small files to smooth places where sand paper cant reach, etc the hole where the cables go through.
Step 4: (Optional) Painting the Lid
The printed lid came out horribly and needed some fixing. Sanding the lid was not enough because there were deep indentations in the surface.
To fix this, apply clear nail polish to the surface wherever you see such indentations and leave it to dry. Repeat this process until the indentations are leveled as much as possible. Avoid painting the logo.
To give a little Raspberry Pi color feel paint the inner letters red and green using nail polish.
Using finer grit sandpaper, again sand the surface to level any excess nail polish.
Before spray painting we need to protect the colored logo somehow. Having no better idea I used some kindergarten clay to cover the logo, and used a utility knife to remove access clay.
The clay will protect the plastic underneath, so make sure the logo is fully covered with it.
Last step is to spray paint the lid in a well ventilated area.
Step 5: Positioning the Cables
Now it is time to take the two cables and insert them through the case opening. The hole for the cables is left intentionally smaller than the plastic cable jacks, so this is impossible to do without modifying the hard rubber jacks.
Using a utility knife or sandpaper slowly remove bits of rubber equally on all sides until the cables can just barely pass through the hole. You can also enlarge the hole using small files, but it is easier to remove the rubber bit by bit.
Insert both cables through the hole, but keep in mind the orientation of the cables. We want the female jacks to align with the two male jacks protruding out of the lapdock.
Now comes the tricky part, which is plugging both female jacks into their male counterparts. File the walls of the hole and cut even more rubber from the jacks until you get them to plug completely.
Once this is done, add a little superglue to hold the jacks in that position, but be careful not to superglue the case to the lapdock. Leave the glue to harden, for half an hour.
Once the glue is set, slowly unplug the enclosure. Now add more glue around the jacks to make sure that they will never move.
Step 6: Software
For software I chose Kodi Krypton, using LibreELEC.
Head over to their site, download the Raspberry Pi Zero LibreELEC image and write it to your microSD card.
You can write the image easily using the tool also available on their site.
Step 7: Securing the Pi in Place
Connect the HDMI and USB cables to the Pi. Make sure to use the OTG USB port on the Pi, and not the power port.
Secure the Pi with 2 M3 Wood screws. The screws need to be about 3mm long so as not to go through the other side of the case.
Bend the cables and fit them inside the case.
Test the system by plugging the case into the lapdock. If all is well you will see your Kodi Krypton booting up.
Step 8: Closing the Lid
Secure the lid with four M3 wood screws, and remove the molding compound to reveal the final finish.
I added another layer of spray paint before removing the clay, because the screws were unpainted.
Step 9: Plug and Play
Plug the πtrix to the dock, and enjoy your media.
The build quality and the battery in this thing are awesome. After four hours of play time at maximum brightness and volume, the battery indicator was still at two out of five bars, which is nice if you plan to carry it when going camping from time to time.