after a couple years since my last attempt (https://cybre.space/@viv/99706957613740002), i built another portable raspberry pi.
specifically, I am using a raspberry pi 3 a+, for size and power consumption. the display is a hyperpixel4.
the power supply is the same adafruit powerboost 1000c I used before, which unfortunately is not powerful enough to drive my pi4. but the pi3a+ is an ok compromise and there are some savings from not having ethernet and a usb hub.
i'm using a chunky 6000mah battery with it so it last ... forever, but is pretty heavy. i didn't really do any battery life testing with my smaller lighter batteries /or/ this one, so that's a change I *might* make in the future...
there was a first version (which is purple), which had a ton of problems
* walls way thicker than they needed to be
* two of the mounting holes for the pi were off and i had to drill new ones
* the thickness of the case meant that the mounting screws i had were not long enough to go through the case and the board to reach the standoffs
* i forgot to put in a dang charging port so I messily drilled one
* corners were not rounded at all so it was sharp to hold
* cutouts for microsd and usb were reversed, I had to rip one of them apart with pliers to get everything to fit together
* I had mounted the pi in an orientation where the hdmi and headphone ports would never be accessible. fortunately, I was able to easily flip it and add a cutout.
by the time I got around to printing the second one, the filament moved on to blue.
one thing that's a pain about using the hyperpixel4 and pi3a+ together is that I have very limited options for input devices. the hyperpixel4 uses all of the gpio pins (though it does expose an alternate i2c interface) and i only have one usb port unless I want to add a hub, so I'm pretty limited in how I can connect other devices.
it'd be really nice to have like, shoulder buttons I can map to modifier keys...
did some more work on this today.
the bluetooth keyboard I'm using is powered by 2 AAA batteries, which makes it a *great* candidate for wiring directly to the pi's 3v pin. doing that, I can reduce the weight of the pi and the distance from the top of the keyboard to the back, which should make it more comfortable to use. theoretically.
the problem is that I then need to design and print a new backplate for the keyboard. the last time I tried to do this for a keyboard... did not go so well, it's pretty hard to get everything aligned on such an irregular shape. I hoped this time would be different (spoiler -- it was, but only a little)
I scanned the back case in a flatbed scanner and hoped that would be close enough. it definitely wasn't.
I guess the problem with trying to build a plate which snaps into an existing part is that your margin of error is very small. my first print was quite off, I measured that to make corrections to the design. and printed a second one (pictured)
oops I screwed up the threading, i got too excited writing about it.
here are the other related toots
https://cybre.space/@viv/104425453476264740
https://cybre.space/@viv/104425491472945273
https://cybre.space/@viv/104425510187949008
here are the guts. the keyboard is attached to a plate that clips into the bottom half, which makes it pretty easy to remove and get inside if I need to.
you might be wondering why the plate is purple, while the rest of the computer is blue. I printed with a color changing filament, and...