It's a tablet! (Rev2 PCB testing)

A project log for Put a Raspberry Pi CM4 into an original iPad

Open up a 2010 iPad, remove its logic board, and fabricate a new board based around the Raspberry Pi CM4.

evanEvan 12/30/2023 at 05:041 Comment

It works!

I ordered the second revision of my PCB a few months back, and have been slowly working my way through testing and debugging the functionality. So far, the PCB hasn't required any modifications -- all the issues I've encountered have been soldering or software issues.

A brief list of things I tested / debugged:

I'm beginning to think that my bismuth-based low temperature solder is a bad idea, especially since the 0.8mm PCB is so flexible.

Anyway, with all those issues worked through, I decided to assemble the whole thing into tablet form (removing the battery wires I had soldered into place for testing purposes) and take a little victory lap.

Next steps

There's still a few more bits of hardware to test:

There's also a bunch of stuff I'd like to do with the dock connector:

Also, Raspberry Pi OS's GUI is barely functional on a tablet:

I'd like to play around with Ubuntu Touch / UBPorts and/or Android. These should provide a much more usable interface.

Some other software improvements to make:

Finally, I'll probably need to do another board revision to get the case to close entirely:

The case can't close properly because the PCB assembly ends up being too thick with the CM4.

I might end up having to make parts of the board out of flex PCB. Basically, the CM4 and its connectors make the board about as thick as it can be and still fit in the case, but the CM4 is on the bottom, and I need some parts on top of the board fairly close to the CM4. If the board were flexible, this might just work.

See how the right side sticks up a bit? That'd be fine, except that the middle needs to be low so that the dock connector PCB (grey strip up the middle) isn't too high. The LVDS connector is a bit of a problem too.


kelvinA wrote 12/30/2023 at 06:57 point

It's quite nice to see all your work come together successfully, though I feel some fear that it's entirely possible for everything to be designed + programmed correctly and yet a suspect solder joint or several is all it takes for issues to arise.

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