Last Updated or created 2024-06-27

Testing the first keyboard. It is the 8085-SDK hex matrix keyboard.

It is running on a Raspberry Pi Zero 2, without X server.
So the images are displayed using the framebuffer.
Also the touch data is read using evdev and the raw devices.

Todo:

• HID part
• Add a rotary button for the selection of the different Keyboard Layouts
• Improvement keyboard matrix calculation to find out which key is being pressed.
• Code to control AT/PS2 computers directly using GPIO pins
• Add a controller to use Raw controlling of matrix pins ( 6502 C64 hardware for example )

Bash test and configuring the OS for testing.

cat <<EOF >> /boot/config.txt
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
display_rotate=3
EOF

# Image testing
apt-get install fbi
sudo fbi -d /dev/fb0 -T 1 8085.png  -a --noverbose

apt-get install python3-evdev python3-uinput evtest
evtest

First simple python test

import select
from math import floor
import sys
slot = 0

keysname=[["F","E","D","C","vect-int","reset"],
          ["B","A","9","8","GO","Single-Step"],
          ["7","6","5","4","Exam-reg","Subst-mem"],
          ["3","2","1","0","Exec","Next"],
          ]
keysnames=[["F","E","D","C","vect-int","reset"],
          ["B","A","L","H","GO","Single-Step"],
          ["PCL","PCH","SPL","SPH","Exam-reg","Subst-mem"],
          ["3","2","1","0",".",","],
          ]

for path in evdev.list_devices():
    device = evdev.InputDevice(path)
    if evdev.ecodes.EV_ABS in device.capabilities():
        break
else:
    sys.stderr.write('Failed to find the touchscreen.\n')
    sys.exit(1)

while True:
    r, w, x = select.select([device.fd], [], [])

    id_ = -1
    x = y = 0

    for event in device.read():

        if event.code == event.value == 0:
           if id_ != -1:
                yy = floor(( x - 600 ) / 700)
                xx = floor(( y - 1377 ) / 226)
                if yy < 4 and yy >=0 and xx < 6 and xx >= 00:
                     if slot == 1:
                         print(keysnames[yy][xx])
                     else:
                         print(keysname[yy][xx])

        elif event.code == ABS_MT_TRACKING_ID:
            id_ = event.value
        elif event.code == ABS_MT_SLOT:
            slot = event.value
        elif event.code == ABS_MT_POSITION_X:
            x = event.value
        elif event.code == ABS_MT_POSITION_Y:
            y = event.value

I came up with a simple matrix calculation

Pressing the 4 corner keys gave me x and y.
I took averages for min and max reading.
I don’t need pixel-perfect reading, and I noticed values between 960 and 3080 vertically.
We want 960 – 3080 into 4 blocks, but the middle should start @ 960.

So 3080/3 = about 700
700 / 2 = 350
block 1 starts 350 sooner than 960 is ~ 600
Upper key y coords = 600-> + 700
Next is 1300 -> + 700
converting to whole numbers using floor gives me:
floor(( y – 600 ) / 700)
NOTE: My x and y are rotated

Example using coordinates
1600, 1600
floor(( 1600 – 600 ) / 700) = floor(1,4…) = 1st row
(from row 0,1,2,3)