Bits and bobs and thoughts on future hardware

Originally published on Patreon.

So. I finally made it back to my workshop in New York yesterday, after more than four months away. Waiting there were some projects that I left behind, as well as some new parts I had ordered from overseas that arrived while I was gone. Just to be clear: priority one is the current Open Book hardware and software; I’m not chasing after a new shiny thing just for the sake of it. But I also recognize that if I ever make a future version of this, it’ll behoove me to think of the future hardware when writing the present software. So, some thoughts! 

The first thing was this 4.3 inch parallel display from Good Display (pictured next to the current 4.2 inch display). This one is really exciting to me. It’s got twice the resolution (800x600) and twice the bit depth (4-bit versus 2-bit), which would mean more room for text and MUCH higher quality images, with eight shades of gray instead of four. Also, since the resolution is exactly double, it means you could run the current UI (targeted for a 400x300 display) in 2x as an accessibility mode.

I was hacking on a FeatherWing to drive this display before I left, but alas, it really never worked. I think I misunderstood something fundamental about the booster circuit, because while I was able to send commands to the PMIC, set the target voltages and even see the “power good” light light up, I never saw the boosted voltages at the test points. (there were also mechanical issues with the connector)

Having said all that, one of the good things about coming back to a problem after four months away is that (hopefully) you’ve learned a lot in the interim. For example: I watched this Desk of Ladyada video back in May, which covered the topic of selecting inductors for a boost converter. What a fortunate coincidence! 

Between that and finally getting a better sense for what’s going on in the current Open Book booster circuit, I think that I’m going to go back to the start on this FeatherWing, spin another revision, and see if I can’t get this screen to display something. I think it’s a worthy candidate for inclusion in a version 2 of the book: similarly priced to the current display (at least in small quantities), and if you’re willing to spend a bit more it has options for the inclusion of either a touch screen or a front light. It also keeps a similar form factor to the current Open Book, and I have to say I really do like the hand feel of  ~4 inch screen. 

Having said that, these also arrived: a couple of recycled 6 inch Kindle screens. I love that they’re so recycled that they’re still displaying the last image that was on them before they were stripped for parts. This is the same display that the Inkplate 6 folks are using, and there’s something I love about the idea of taking apart an old Kindle and turning one of its parts into a screen for a libre device. I think the driver board for this screen will be very similar to that FeatherWing above, although it does use a different connector than the 4.3 inch display. 

Finally, this is actually something I ran across back in Texas when I was cleaning out old boxes: a design prototype (no electronics) that predates even the current design of the Open Book. Before the Open Book had this name and this form factor, I was imagining a miniature device, like the medieval books of hours that monks would carry around at the turn of the first millennium. I called it the “Devotional”.

Anyway, I didn’t pursue this little folding form factor book, but there are a couple of reasons that it’s back on my mind: for one, Good Display just added a touch screen variant of the display that the Devotional was targeting. And two, while at the time I had no idea how I would connect the two sides of a hinged device, over the last few months I’ve been building a lot with the 9-pin JST-SH connector that Adafruit uses on their MONSTER M4SK, to connect the two eyes when the mask is broken in half. I’m realizing I could use the same strategy here. Point is, I think I see now how I could make this gadget work. 

Will I build all these things? Almost certainly not. Will all these things be built? Maybe! I guess I’m sharing the thoughts in case it inspires anyone else to build in this direction.