wanting a more powerful, fully linux capable palmtop
for a while, i went ahead and Gutted a 1990's HP95LX
and transplanted new brains in the form of a Raspberry PI zero w + bits
4.3" LCD 800X480 Run directly DPI on GPIO's
capacitive touch screen (not hooked up yet)
Stereo speakers + mic (USB)
Raspberry pi webcam planned
microusb LiPO Charger
full size 10/100 Ethernet (USB)
Full size USB 2.0
full size RS232 level serial port (USB)
Infrared dataport cover, gives access to TF-CARD
Full size USB 2.0
Full Size HDMI
Raspberry pi zero w, usb hub, battery charger circuit, LCD backlight boost converter,
I reverse engineered the keyboard membrane, and used a Teensy to use it as a USB keyboard, and in combination with a custom linux keyboard layout file,
all the printed Chars, special chars etc., function keys. work as intended
"special menu buttons" have no use yet
The parts used, where mainly chosen by the immediate availability in my box of bits. and may NOT be the best parts for the job.
Lithium-Ion, power management I used an TP4056 based micro USB -> Lithium-ion battery charger board, to charge the lithium-polymer battery, it includes Under voltage cut-off to protect from undercharging the battery (i don't believe its ideal for lithium-polymer batteries, but does the job)
Raspberry pi zero power / USB 5V the raspberry pi needs 5V for power, as well as for the USB ports, I used a MT3608 based boost converter module to step this up from the battery voltage while they appear to be "rated" for 2A I'm probably driving it a bit hard.
LCD adapter and back-light. I did not buy a module to interface with the LCD, I repurposed an old board i had with the 40pin LCD connector, I did point to point wiring to the raspberry pi GPIO header combined this with a SX1308 based boost converter module to step the battery voltage up to 23v for the LED back-light
I would consider getting a dedicated LCD interface module. possibly with the back-light step up, there are a few out there (having the boost convert separate, may make it easier to make it fit somewhere.)
most of the "cheap Ebay boards" had to be modified,
cut down, or split up to fit the constrains of the case.
it fits together with the boards stacked and positioned closely to "almost" fully utilize the volume.
The screen contains the USB sound card, a small amplifier. and adapter board for the LCD
under the one speaker and the LCD itself