Psion Pi

Personal electronics project; Attempting to build a modern PDA clamshell computer in a likeness of the venerable Psion 5mx.

4 years into this project, some significant changes, namely wide screen, LG Phenom keyboard and Pi 4 (significantly more capable.. the previous Zero/Zero 2/3 all put me off)

Aims

Tasty colour screen - For enjoyable video playback
Quality keyboard - So it's legitimately useful
Portability - I'm under no illusions that it'll be larger than a Psion 5mx/Jornada (as would be ideal) because of screen size and battery demands but if it's smaller than a Netbook Pro I'll be happy
Sturdiness - Every single bit will be inherently fragile as heck, so I need to 3D print the structure real good

Ingredients

Battery pack (18650 3S parallel 3.7v) - Home-made li-ion for the win!
Charging circuity and steps ups with protection - So I don't blow myself up
Raspberry Pi
LG Phenom keyboard, or maybe Psion Netbook (previously Psion 5mx, prepreviously Dell Foldable) - What? No way! Yes way. Yes frickin way
Keyboard USB interface - Arduino or ESP8266, hand-built
7.9" Capacitive Touchscreen LCD 1024*600 (Waveshare C Rev2.1)
Mad efficient 1337 OS and warez, legit IDE, etc - We'll start with vanilla Raspbian first though

"Wait, so what's this repo even for then?"

Notes about how I set everything up for reference, config files, microcontroller code for keyboard interface, etc etc.

Setting up the Pi

Raspbian Stretch (2017-08-16) did not work, no matter what (with Pi Zeroes).

Raspbian Jessie (2017-07-05) did though, but more recently..

Raspberry Pi OS Bullseye (2021-11-08) is 64-bit(!)

Installed on a 16gb microSD with win32diskImager (or similar) then, before removing, (in the windows partition, or /boot on unix):

Create a blank file called ssh on it, e.g.

cd /d h:
echo > ssh

Create wpa_supplicant.conf containing:

country=US
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
 ssid="NetworkName"
 scan_ssid=1
 psk="yourpassword"
 key_mgmt=WPA-PSK
}

Safely eject (they can become corrupt, trust)
Pop it in the Pi with HDMI and a keyboard; let it do its thing.

Any screen problems and it should still be SSH-able.

LCD Screen - 7.9" Waveshare Widescreen 400×1280

Enable HDMI current and whatnot

sudo nano /boot/config.txt

# Add support for 7.9" Waveshare LCD
# set current over USB to 1.2A
max_usb_current=1
hdmi_group=2
hdmi_mode=87
hdmi_timings=400 0 100 10 140 1280 10 20 20 2 0 0 0 60 0 43000000 3
# 1: 90°; 2: 180°C; 3: 270° (might not work, see next section)
#lcd_rotate=3
#hdmi_enable_4kp60=1

Disable compositor

sudo raspi-config

6 Advanced menu then A3 and set Compositor to disabled.

Rotate

Set orientation (right) in raspbian preferences > screen configuration. This appears to have a bug where the settings don't persist after boot - it creates a file called dispsetup.sh but doesn't appear to run after login, at least on my current distro, so let's force it:

sudo nano /etc/xdg/lxsession/LXDE-pi/autostart

Append:

@/usr/share/dispsetup.sh

Touch Setup

Automatic and orientated by long-pressing the 'rotate touch' button on the screen.

Brightness

Powers happily from the touch USB input!!

Has 5 Settings, long press on/off on screen:

1 0.15A
2 0.16A
3 0.17A
4 0.19A
5 0.2A

Fan Shim

git clone https://github.com/pimoroni/fanshim-python
cd fanshim-python
sudo ./install.sh
cd examples
sudo ./install-service.sh --on-threshold 65 --off-threshold 55 --delay 2

Overclock

Make sure to use the fan shim!

sudo nano /boot/config.txt

# Overclock (all values typically unset, defaulting to 700mhz)
over_voltage=4
arm_freq=2000

More steps involved.. https://www.tomshardware.com/how-to/raspberry-pi-4-23-ghz-overclock

Other settings

Disable dimming, etc.. https://www.waveshare.com/wiki/7.9inch_HDMI_LCD

Power Usage

Component	Usage (Amps +/- 0.05)
Pi Zero W	0.15 (unused)
Pi 3	0.3 (idling)
Pi Zero 2 W	0.3
Pi Zero 2 W (Overclocked)	0.45

Pi 4	0.55 (idling)
7.9" Screen	0.65

Total	1.2

Battery life estimates, according to my Super Useful Tool:

18650 x 1 (2500mah) = ~1h

18650 x 3 (7500mah) = ~3h

Mine are 20A maximum discharge. If they're in parallel, you get more mAh and current capability, as it's shared around. And anyway, 20A discharge? Fokk man, it'll be nowhere near. I just need a nice chonky boost module. If it doesn't work, build a series one with 15A BMS etc.

Keyboard

I got reasonably far in this repo with keyboard emulation on the Pi itself but.. I don't love it, and since then I reckon I've nailed keyboard matrix scanning so I plan to pick a microcotroller with suitably choppy USB capabilities (32u4/STM32/Tiny?) to capture the input and emulate a USB keyboard. Much cleaner!

OBSOLETE: Previous foldable keyboard

Dell Axim X5 Foldable Keyboard - what a hero of a warlock of a battlemage of a keyboard! Disassembling it revealed it only has three IO:

3.3V in
GND
Data out

Hooking that all up to a USB FTDI (data => RX), reveals some useful output with the following settings (e.g. in RealTerm): Port -> Baud: 4800, Display -> Display As: Hex

Keymap

This wonderous diagram is courtesy of Gavin Whelan, along with generally pointing me in the right direction to capture input.

|------||------||------||------||------||------||------||------||------||------||------||-----||-----||--------|
|  `~  ||  1!  ||  2@  ||  3#  ||  4$  ||  5%  ||  6^  ||  7&  ||  8*  ||  9(  ||  0)  || -_  ||  =+ ||  <-    |
| 0ef1 || 16e9 || 1ee1 || 26d9 || 25da || 2ed1 || 36c9 || 3dc2 || 3ec1 || 46b9 || 45ba || 4e  ||  55 || 718e   |
|      ||      ||      ||      ||      ||      ||      ||      ||      ||      ||      || b1  ||  aa ||        |
|------||------||------||------||------||------||------||------||------||------||------||-----||-----||--------|
|--------||------||------||------||------||------||------||------||------||------||------||-----||-----||------|
|  ->|   ||  Q   ||  W   ||  E   ||  R   ||  T   ||  Y   ||  U   ||  I   ||  O   ||  P   || {   || }   ||  |\  |
| 0df2   || 15ea || 1de2 || 24db || 2dd2 || 2cd3 || 35ca || 3cc3 || 43bc || 44bb || 4db2 || 54ab|| 5ba4|| 5da2 |
|        ||      ||      ||      ||      ||      ||      ||      ||      ||      ||      || [   || ]   ||      |
|--------||------||------||------||------||------||------||------||------||------||------||-----||-----||------|
|----------||------||------||------||------||------||------||------||------||------||------||------||----------|
|  caps    ||  A   ||  S   ||  D   ||  F   ||  G   ||  H   ||  J   ||  K   ||  L   ||  ;:  ||  '"  ||  enter   |
| 58a7     || 1ce3 || 1be4 || 23dc || 2bd4 || 34cb || 33cc || 3bc4 || 42bd || 4bb4 || 4cb3 || 52ad || 5aa5     |
|          ||      ||      ||      ||      ||      ||      ||      ||      ||      ||      ||      ||          |
|----------||------||------||------||------||------||------||------||------||------||------||------||----------|
|--------------||------||------||------||------||------||------||------||------||------||------||------||------|
|  shift       ||  Z   ||  X   ||  C   ||  V   ||  B   ||  N   ||  M   ||  ,<  ||  .>  ||  /?  ||  ^   ||  rsh |
| 12ed         || 1ae5 || 22dd || 21de || 2ad5 || 32cd || 31ce || 3ac5 || 41be || 49b6 || 4ab5 || 28d7 || 59a6 |
|              ||      ||      ||      ||      ||      ||      ||      ||      ||      ||      ||  |   ||      |
|--------------||------||------||------||------||------||------||------||------||------||------||------||------|
|------||------||------||------||------------------------------||------||------||------||------||------||------|
|  fn  || ctrl ||  win ||  ie  ||           space              || alt  || ctrl ||  del || <--  ||  |   ||  --> |
| 02fd || 14eb || 07f8 || 708f ||           5ca3               || 11ee || 738c || 6699 || 5ea1 || 609f || 2fd0 |
|      ||      ||      ||      ||                              ||      ||      ||      ||      ||  v   ||      |
|------||------||------||------||------------------------------||------||------||------||------||------||------|

OBSOLETE: Previous LCD screen attempts

7.9" on Pi Zero 2

GRAPHICS? Apparently an advanced graphics thing? Needs experimentation though:

sudo nano /usr/share/X11/xorg.conf.d/99-fbturbo.conf

Comment out the line, a la:

#       Driver          "fbturbo"

TOUCH?

sudo apt-get install xserver-xorg-input-libinput
sudo mkdir /etc/X11/xorg.conf.d
sudo cp /usr/share/X11/xorg.conf.d/40-libinput.conf /etc/X11/xorg.conf.d/
sudo nano /etc/X11/xorg.conf.d/40-libinput.conf

Find the touchscreen section and add one of the following lines, a la:

Section "InputClass"
        Identifier "libinput touchscreen catchall"
        MatchIsTouchscreen "on"
        # Option "CalibrationMatrix" "0 1 0 -1 0 1 0 0 1" # mykemod
        # Option "CalibrationMatrix" "0 1 0 -1 0 1 0 0 1" # mykemod 90 deg
        # Option "CalibrationMatrix" "-1 0 1 0 -1 1 0 0 1" # mykemod 180 deg
        Option "CalibrationMatrix" "0 -1 1 1 0 0 0 0 1" # mykemod 270 deg
        MatchDevicePath "/dev/input/event*"
        Driver "libinput"
EndSection

7" Waveshare

Either copy the config.txt in this repo, or bosh this stuff into yours (in windows partition or /boot on unix):

# Add support for Waveshare 7" capacitive Touch (C) v2.1
# set current over USB to 1.2A
max_usb_current=1

# overscan to adjust image position
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0

# HDMI config
hdmi_drive=1
hdmi_ignore_edid=0xa5000080
hdmi_group=2
hdmi_mode=87

# 1024x600 display
hdmi_cvt=1024 600 60 6 0 0 0

5" model A screen

Elegoo, a cheaper version of Wavershare model A (not B)

cd ~
wget https://github.com/entozoon/psion-pi/raw/master/lib/LCD-show-170703.tar.gz
tar xzvf *.tar.gz
rm *.tar.gz
cd LCD-show/
chmod +x LCD5-show
./LCD5-show

3.5"

Raspbian Stretch (2017-11-29)