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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.
83 lines
3.0 KiB
Markdown
83 lines
3.0 KiB
Markdown
# Bluetooth to LK201 bridge for DEC video terminals
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<img src="./images/vtbt.jpg" width="30%"/> <img src="./images/vtbt_with_devkit.jpg" width="30%"/>
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This repository contains Zephyr RTOS firmware code and KiCad hardware files for
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a device which interfaces a DEC VT to a Bluetooth keyboard via an emulated
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LK201 interface.
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The vtbt board has a socket for an ESP32-C3-DevKitM-1 which provides the
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microcontroller and Bluetooth functionality (as well as 3.3V regulation). The
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vtbt provides power from the keyboard interface's 12V supply, performs RS-423
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level conversion for the serial interface and has the four LEDs and magnetic
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buzzer found in a real LK201 because Bluetooth keyboards are unlikely to have
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those.
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I built this after I spent great effort to obtain a VT420 but then neglected to
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use it due to frustrations with the infamous LK401 keyboard. Once I got the
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vtbt capable of "self-hosting", I used it with my VT420 to finish developing
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the firmware over a serial console. I found that the terminal actually provides
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a very enjoyable and relaxing experience with a decent keyboard!
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## What works
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Everything documented in the VCB02 Video Subsystem Technical manual is
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implemented including:
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* Beeps, keyclicks, beep and keyclick volumes
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* The four LK201 LED indicators
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* Per-key-division auto-repeat, up-down, down-only modes
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* All mode-setting operations for changing modes and auto-repeat timings
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## What doesn't work
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I've only tested the vtbt with DEC VT420 terminals.
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The key mapping is set up for the VT420's default "<> Key Sends `~" and "`~ Key
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Sends ESC" settings. It may need adjustment for other terminals or
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configurations.
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Similarly, Alt keys, which are disabled by default on the VT420, are not
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supported, but support could be added.
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Compose keys have not been tested.
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## Usage
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1. Build and flash the firmware to an ESP32-C3-DevKitM-1 connected over USB.
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From a Zephyr environment:
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```west flash```
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2. Mount the ESP32-C3-DevKitM-1 on the vtbt with the USB port facing the vtbt's
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modular connector and the ESP32-C3 and antenna on the side with the LEDs.
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3. Connect the vtbt to a DEC terminal with a rollover-wired 4P4C module cable
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(like a phone handset cable).
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4. Turn on the DEC terminal. The vtbt will display the terminal's power-up
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self-test sequence on its four LEDs followed by a beep.
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5. Connect to a Bluetooth keyboard.
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The firmware indicates Bluetooth status via the ESP32-C3-DevKitM-1's RGB
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LED.
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Blue means it is searching for a Bluetooth keyboard.
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Green means it has found a keyboard and is awaiting authorization. To
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authorize, type 123456<Enter> on the keyboard.
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Orange means it is connected to a keyboard and processing keyboard events.
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The firmware stores bonded devices and automatically reconnects to them.
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## Development
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The vtbt's modular connector blocks the ESP32-C3-DevKitM-1's USB port, but for
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quicker iterations a pair of pin headers as spacers will make it taller.
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vtemu.py in this repository can be used as a basic emulation of a DEC terminal
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for testing.
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