The idea is to have a cell phone sized Linux computer with an actual keyboard. t is based on the Raspberry Pi Zero and I'll be using a 3.5" LCD for the display.
The keyboard for the first version is going to be a Blackberry Q10 keyboard. We'll see how well that works. I'm actually building it as a module that plugs in to the Palmtop, and will also work as a USB keyboard. Oh and it'll run the QMK keyboard firmware.
I'm still trying to decide on batteries, but the first version will probably be an 18650, my poor math skills give me 2-3 hours of runtime.
Right now it all exists in schematics and pcb designs in the cloud. I'm slowly collecting parts and saving up for my first pcb order.
Which basically means that if I only need to detect 2 keyboard buttons pushed at once I don't need diodes. Also the raspberry Pi Pico supports qmk now so I think that's going to be my keyboard controller.
Still in waiting mode... the Keyboard connector breakout boards have been ordered from JLCPCB and they shipped yesterday so they just have to make thier journey across the ocean to my door. I've also ordered 10 of the special connectors from Digikey and those are on the way too.
On Friday I also received my solder reflow plate, yay! I used it to remove some random surface mount components from an old hard drive PCB and it worked like a dream, I can't wait to start using it.
Oh, I also ordered a Raspberry Pi Pico (RP2040) from Digkey as well. Although I have 2, the Atmega processor I've been planning on using as they keyboard controller is pretty much unobtainium at the moment, and right now it's actually more expensive than an RP2040.
I'm waiting for the following right now:
* Solder Paste - Aliexpress
* PCBs - JLCPCB
* Keyboard Conector - Digikey
* Raspberry Pi Pico - Digikey
Once I get those parts the next step is to build a prototype working USB keyboard with the BBQ10 keypad. Fun on the bun.
The first step for this project is to have a functioning USB Keyboard (which can be used separate or integrated with the palmtop directly. This is the part of the project that has the most unknowns to me so I'm tackling it first.
I already have a USB Keyboard PCB design based on the Blackberry Q10 keyboard, the teeny tiny "BM14B(0.8)-24DS-0.4V(53)" connector and an ATMEGA32A-PU (which will run the QMK Firmware). There is some excellent documentation on this Github project that I'm working off of. I would love to just have some of the boards manufactured and get on with the palmtop design, however there are still some unknowns (to me).
How do I control the backlight LEDs? There are 4 pins on the connector for the LEDs but I haven't been able to find any information on how to control them.
How can I use the MEMS Microphone that's built in to the keyboard? This isn't a must but it would be incredibly useful to be able to use that built in microphone.
Does the keyboard have built in diodes to prevent key ghosting, or will I have to include those in my design?
Are there any other Gotchas in interfacing the keyboard that I should know before finalizing the keyboard design?
So as a first exploratory step I've designed a breadboard friendly breakout board for the keyboard. (I got the idea from this project) I'm getting the boards produced by JLCPCB and if they work I plan to sell them at a local cost if anyone is interested - I'm kind of hoping this will help me finance the next steps of the project although that may just be a pipe dream.
Additionally I haven't really done much surface mount soldering work and this connector is way to small (for me) to consider hand soldering. With that said I have one of These cheap reflow plates from Aliexperess on order. I know it's not the best but it seems like a good place to get started.
Next up for the project: waiting. Waiting for the PCBs to be manufactured and delivered, waiting for the reflow plate to arrive, waiting for the connectors to arrive... it's all coming from China so the waiting is usually on the order of months - but it's cheap and that makes it easier to learn!