SDD
3fd1e13b2e
Distils public docs into reference/keyboard-mouse/PROTOCOL.md for the level-1 Keyboard (27) / Mouse (26) device tests: - keyboard: 4800 8N1 RS-423, self-test via FD -> 01 00 00 00 (errors 3D/3E) - mouse: 4800 8O1 RS-232, self-test via 'T' -> 4-byte report (errors 3D/3E, >=0x20 fatal) - separate ports: DUART2 A=keyboard, B=mouse (NOT daisy-chained) MAME already has an LK201 device (src/mame/dec/lk201.cpp/.h) but no DEC mouse.
4.0 KiB
Digital Equipment LK201 keyboard emulators
The emulator allows a standard PC-style keyboard to be used as a replacement for a DEC LK201 keyboard. This is useful if you don't have an LK201 keyboard, or if all the ones you have stopped working, as happened to me.
There are now two emulators: one for USB keyboards, and a different one for PS-2 (round connector) keyboards. The circuit for the two is rather different, but the software functionality is the same for both.
The USB emulator circuit has two connectors: a modular jack which accepts the LK201 keyboard cable, and a USB connector. The USB connector on the Trinket board is a micro-B connector; your keyboard presumably needs an A jack. There are various ways to convert from one to the other; Adafruit sells one.
The PS2 emulator circuit has a modular jack for the LK201 keyboard cable and a standard PS2 mini-DIN connector for the keyboard. If you have a very old PC keyboard with a standard size DIN connector (5 pins), you'll need an adapter for that; the board design I created does not accommodate a standard size connector. Note that those old keyboards may have fewer keys, in which case you may want to adjust the key mapping in the software. Also, some of them draw too much current for the regulator on the Arduino board. If so, you will need to modify the circuit to add an external 12 to 5 volt regulator to feed the PS2 keyboard jack, rather than relying on the 5 volt out from the Arduino board.
Keyboard mapping
For the most part, the keys on the PC keyboard correspond directly to the same keys on the LK201. This applies to all the letters and digits as well as most punctuation. Similarly, F1 through F12 are the same in both, as are the cursor keys and most of the numeric keypad keys. Both shift keys are shift, but only the left control key is control.
Some other keys are different on the two keyboards. Sometimes similar key labels exist but the positions are different; in that case I have chosen to map the keys by their positions.
| PC keyboard key | LK201 key |
|---|---|
| Left Windows | < > |
| Left Alt | Compose |
| Esc | F11 |
| Insert | Find |
| Home | Insert Here |
| PgUp | Remove |
| Delete | Select |
| End | Prev Screen |
| PgDn | Next Screen |
| PrtScr | F14 |
| Scroll Lock | Help (F15) |
| Pause | Do (F16) |
| Right Alt | F17 |
| Right Windows | F18 |
| App Menu | F19 |
| Right Control | F20 |
| Num Lock | PF1 |
| Num keypad / | PF2 |
| Num keypad * | PF3 |
| Num keypad + | Num keypad , |
Note that the PF4 and F13 keys are not available, I ran out of places to put them.
Also, on PS2 keyboards due to an oddity in the way the key is handled, the Pause key (used for the LK201 "Do" function) does not support LK201 up/down modes and will not auto-repeat. The keyboard always pretends that this key is immediately released, so it is not possible to simulate the normal operation.
Lights
Standard PC keyboards have only three LEDs, while the LK201 has four. The mappings are:
| PC keyboard LED | LK201 keyboard LED |
|---|---|
| Scroll lock | Hold screen |
| Caps lock | Lock |
| Num lock | Compose |
The WAIT light is not on the keyboard but is provided by the LED on the center of the Arduino board. On the USB version, that is a multi-color LED, set to green for the WAIT indicator. On the PS2 board, this LED is red.
Trinket middle LED color coding (USB keyboard emulator)
When operating, the emulator uses the middle LED for the LK201 WAIT light, in green. Other colors are used during initialization, to reflect the phases of the USB discovery.
- Purple: settling.
- Blue: waiting for device. This is the code you will see when no keyboard is plugged in.
- Yellow: attached, reset device.
- Orange: wait for device reset complete.
- Cyan (light blue): configuring device. If the board stays in this state, the USB device is not compatible with this software.
When the USB initialization completes, there is a brief bright green flash.