I am not interested in any argument about Why we would want a Pi PDA.
The answer is simple, because we Can make them in a varity of sizes.
I am interested in How.
I have been doing my research.
PalmOS morphed into WebOS, which is just another me too, Internet connected OS.
Alternative OS's are scarce too, the only interesting new one for me is Redox OS.
So I am now thinking about DIY OS based on Ultibo.
Not because I hate Linux but becuase I want to learn how OS's work.
Linux also takes time to boot, serious geek foo is needed to improve that.
PDA's are most single user, single purpose OS's, Linux is a bit of a sledge hammer for this.
And becuase I have yet to find a good UI that runs on small screen, recent Orville viewing has convinced me to roll out my own theming UI.
The amount of information about using OpenVG for UI's is nearly nonexistant.
Need to go back 10years to get information and examples for Broadcom OpenVG UI's must be top secret.
But with Pi's a simple uSD card swap fixes the OS situtation.
eReaders now seem to be mostly iMX6 based Linux hardware.
The iMX6 is no powerhouse a Zero could be underclocked
Hardware wise, displays are a big issue.
Manga Screen 2 looks like the best small screen, but will not make small PDA.
Hyperpixel looks a poor cousin now at 800x480 4" but it has the touch screen.
Front mounted touchscreens do effect screen brightness and contrast.
Adafruit has a nice IPS 240x240 display but it is small at 1.5"
Oled would save power but not easy to get in a good enough resolution.
The new ClearInk displays look like they will finally give daylight screens at faster speeds than eInk.
Becuase ClearInk is first targeting Chinese school computing perhaps RPF will adopt them too?
Maybe not this year for PDA use as largish and wearable is their market segment at the moment.
Could a Zero and small screen make a wearable?
Probably, but a bit power hungry, why not use a Zero as HDMI output device.
eBooks have been on all my PDA's and Tablets and Phones, even my MP3 players.
I just tested my HDMI car screen it can power the Zero from the USB port.
Now to check my TV's USB port. HDMI screens are everywhere now
A Zero W may run from the USB ports which gets net connection if needed.
But offline readers are more likely to be read without net distractions
A SD swap with Retropie is also possible if bored with books. How can anyone be bored with books?
Powering from the screen solves the battery issue, but is not that portable.
Then there is the interface problem, only one USB port.
Bluetooth mouse keyboard combo?
Or what about exploring new options like this.
It would fit in the existing Pi Zero case.
DIY touch panel, even microswitchs on the GPIO, all doable.
But means carrying around two cables and needing a HDMI screen.
Good for home based semi permanent use?
Most TV's now have multiple HDMI inputs
Combo/modular system, PDA Zero with plug in Power and screens.
Not ideal but doable, power could be quick swap cells 18650 Li-Ion/LiFePO4 instead of custom lipo.
But there are now Graphne based lipo cells that have many more charge cycles and so will last longer.
Wrist mounted gaunlet Zero based PDA, doable.
Dual screen eInk and IPS LCD?
Tablet size PDAs, well most people use those for surfing the web, probably better using the new CM3+ for that.
Modern browsers need lots of cpu grunt these days.
A Pi phone? Why not?
Some people actually don't like the closed source of current ones and Android apps that want to know everything about you.
The Microbit makes a nice BLE interface to Pi's, could it be used for a wireless Chorded/motion input device?
Just a few option of so many options, what to do first?
For me right now it's learning about file managers and calculator source code.
https://hackaday.com/2018/05/18/open-so ... mentation/
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges