RaspiElf Keypad
Intro
The Elf Membership Card has 8 data switches, 3 mode switches, and a IN push button on its front panel. The data is displayed on 8 LEDs (binary). It is a error prone but educational task to "switch in" in (load) the program.

I have got an old external keypad because my old notebook did not have any numeric keypad. The keys looks similar to those old Elf hex keypads, why not use this spare keypad for the Elf Membership Card? It is a Cherry keyboard and I have an other Cherry keyboard with the same type of key caps and it was easy to replace the two upper rows with the A to F caps.

Hardware

gal 2000 G84-4700 2 persp.jpg
Cherry Keypad G84-4700, original key caps
hex-keypad.jpg
Hex Keypad
keypad-display.jpg
Keypad and display

Short Mode Key Keycode Notes
IN Input I, [CR] 96  
LD Load L, + 78  
R/S Run/Wait R, . 83 R/S is a reminiscence of HP pocket calculators
MP Memory Protect M, - 74  
SW Switch/Keypad S, [BS] 14  

Software for the Raspberry Pi

No special software needed. Keyboard drivers are already built in Raspbian.

Here some ideas if you want to customize your own keypad.

pi@cosmac:~/elf/RaspiElf/tools $ $ test-key /dev/input/by-id/usb-046a_0014-event-kbd
Code: 82 0x52, value 1 key 0 pressed
Code: 82 0x52, value 0 key 0 released 
Code: 79 0x4f, value 1 key 1 pressed
Code: 79 0x4f, value 0 key 1 released
Code: 80 0x50, value 1 key 2 pressed
Code: 80 0x50, value 0 key 2 released
Code: 81 0x51, value 1 key 3 pressed
Code: 81 0x51, value 0 key 3 released
Code: 75 0x4b, value 1 key 4 pressed
Code: 75 0x4b, value 0 key 4 released
Code: 76 0x4c, value 1 key 5 pressed
Code: 76 0x4c, value 0 key 5 released
^C

pi@cosmac:~/elf/RaspiElf/tools $ udevadm info /dev/input/by-path/*-usb-*-kbd
P: /devices/platform/soc/3f980000.usb/usb1/1-1/1-1.2/1-1.2:1.0/0003:046A:0014.0002/input/input1/event0
N: input/event0
S: input/by-id/usb-046a_0014-event-kbd
S: input/by-path/platform-3f980000.usb-usb-0:1.2:1.0-event-kbd
E: BACKSPACE=guess
E: DEVLINKS=/dev/input/by-id/usb-046a_0014-event-kbd /dev/input/by-path/platform-3f980000.usb-usb-0:1.2:1.0-event-kbd
E: DEVNAME=/dev/input/event0
E: DEVPATH=/devices/platform/soc/3f980000.usb/usb1/1-1/1-1.2/1-1.2:1.0/0003:046A:0014.0002/input/input1/event0
E: ID_BUS=usb
E: ID_INPUT=1
E: ID_INPUT_KEY=1
E: ID_INPUT_KEYBOARD=1
E: ID_MODEL=0014
E: ID_MODEL_ENC=0014
E: ID_MODEL_ID=0014
E: ID_PATH=platform-3f980000.usb-usb-0:1.2:1.0
E: ID_PATH_TAG=platform-3f980000_usb-usb-0_1_2_1_0
E: ID_REVISION=0100
E: ID_SERIAL=046a_0014
E: ID_TYPE=hid
E: ID_USB_DRIVER=usbhid
E: ID_USB_INTERFACES=:030101:
E: ID_USB_INTERFACE_NUM=00
E: ID_VENDOR=046a
E: ID_VENDOR_ENC=046a
E: ID_VENDOR_ID=046a
E: MAJOR=13
E: MINOR=64
E: SUBSYSTEM=input
E: USEC_INITIALIZED=69042133468
E: XKBLAYOUT=gb
E: XKBMODEL=pc105

Mapping scancodes to keycodes is universal and not specific to Linux console or Xorg, which means that changes to this mapping will be effective in both.

showkey --scancodes

evdev:input:bvpe-

File /etc/udev/hwdb.d/10-hexkeypad.hwdb

evdev:input:b*v046ap0014* # ML4700
 KEYBOARD_KEY_45=a  # bind numlock to A
 KEYBOARD_KEY_62=b  # bind /       to B
 KEYBOARD_KEY_37=c  # bind *       to C
 KEYBOARD_KEY_01=d  # bind ESC     to D
 KEYBOARD_KEY_1d=e  # bind Ctrl    to E
 KEYBOARD_KEY_38=f  # bind Alt     to F

pi@cosmac:~ $ ls -l /dev/input/by-id/
total 0
lrwxrwxrwx 1 root root 9 May 14 20:23 usb-046a_0014-event-kbd -> ../event0
pi@cosmac:~ $ ls -l /dev/input/by-path/
total 0
lrwxrwxrwx 1 root root 9 May 14 20:23 platform-3f980000.usb-usb-0:1.4:1.0-event-kbd -> ../event0
pi@cosmac:~ $ ls -l /dev/input/event0
crw-rw---- 1 root input 13, 64 May 14 20:23 /dev/input/event0

pi@cosmac:~ $ cat /dev/input/event0 | hexdump -C

ESC
00008010  cb d9 f9 5a cc fd 04 00  04 00 04 00 29 00 07 00  |...Z........)...|
00008020  cb d9 f9 5a cc fd 04 00  01 00 01 00 01 00 00 00  |...Z............|
00008030  cb d9 f9 5a cc fd 04 00  00 00 00 00 00 00 00 00  |...Z............|
00008040  cb d9 f9 5a b8 7a 05 00  04 00 04 00 29 00 07 00  |...Z.z......)...|
00008050  cb d9 f9 5a b8 7a 05 00  01 00 01 00 00 00 00 00  |...Z.z..........|
00008060  cb d9 f9 5a b8 7a 05 00  00 00 00 00 00 00 00 00  |...Z.z..........|

Ctrl
00008070  cf d9 f9 5a 66 55 06 00  04 00 04 00 e0 00 07 00  |...ZfU..........|
00008080  cf d9 f9 5a 66 55 06 00  01 00 1d 00 01 00 00 00  |...ZfU..........|
00008090  cf d9 f9 5a 66 55 06 00  00 00 00 00 00 00 00 00  |...ZfU..........|
000080a0  cf d9 f9 5a 94 f1 06 00  04 00 04 00 e0 00 07 00  |...Z............|
000080b0  cf d9 f9 5a 94 f1 06 00  01 00 1d 00 00 00 00 00  |...Z............|
000080c0  cf d9 f9 5a 94 f1 06 00  00 00 00 00 00 00 00 00  |...Z............|

How to get and build the RaspiElf Keypad/Display Software

The elfdisplay is part of the tools package. See RaspiElf#How_to_get_and_build_the_RaspiEl

Sample session

-- Peter Schmid - 2018-05-03

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