05.10.2015 - Microbook, mk 2
It would have been good for it to have an e-ink screen, to be thinner, the screen to be larger, etc.
Such was the feedback for Mk. 1, that i couldn't fulfill for a while.
Then, i found out that there are documented e-ink displays in open sale.
http://www.pervasivedisplays.com sells them, and they are not at all that hard to interface.
I got a demo board from them, and knew at once that this is the kind of screen Microbook needs.
Unfortunately, to fit the screen interface within it's own size was a task outside my home PCB etching capabilities.
| Thin traces. Very thin, very close|
At first, that was a show-stopper - what is the point of an open-source hardware project that can't be made at home?
But really, it's not that big of an issue, apparently.
So, i went to
the Dark Side PCBCart, and got a few boards made.
It was an interesting experience - i have gone over the design many times, checked the reference schematics for the screen interface several times over, looked closely at the demo board, simulated the charge/discharge circuitry, etc.
Still, the fact remained that i was sending PCBCart a board i haven't actually made and tested myself - that never happened before.
But it came out ok.
The display from the demo kit fit in nicely, and worked from the first try.
(Well, the second. Lesson learned - don't try to test things at 3am and sleepy - you WILL screw up even a blinking LED program, and spend hours looking for a hardware fault that doesn't exist.)
The result is a nice, flat package with a big, low-power screen.
I also added an USB charging port, in case the sun wasn't available.
The "perk" of the design - a solar panel on the back to charge it anywhere from free energy.
Might not look like much, but there are 4 of the Mk. 1 models out there with a much more power-hungry screens and no other charging option, that worked for years without ever running out of charge.
Under the panel, a typical li-po cell.
I wanted to put it under the screen, but they don't make cell that thin, apparently.
No idea how long it would last without a charge this time.
But i hope for years.
There are still a lot to tweak and a proper software to write (update times with the Mk. 1 FW are atrocious), so the design files will follow later.