MyKVM

A KVM-over-IP solution running on Raspberry Pi Zero 2 W, featuring hardware H.264 encoding and a built-in web frontend.

Features

• Low Power: ~1-2W average consumption, powered and controlled through a single USB cable
• HDMI Capture: Captures video input via TC358743 HDMI-to-CSI bridge (up to 1080p25)
• Hardware H.264 Encoding: Zero-copy encoding using Raspberry Pi's bcm2835-codec with DMABUF
• USB HID Emulation: BIOS-compatible keyboard and mouse emulation via USB OTG
• HTTPS Web Server: Built-in secure web server with WebSocket for real-time streaming
• Web Frontend: Retro CRT-style interface with WebCodecs video decoding
• E-Paper Display: Optional status display on 2.13" E-Paper (Waveshare EPD_2in13_V4)

Images

Hardware Requirements

• Raspberry Pi Zero 2 W
• TC358743 HDMI-to-CSI bridge module
• USB cable connecting Pi's data port to target machine
• (Optional) Waveshare 2.13" E-Paper display V4

Prerequisites

Raspberry Pi Configuration

Add the following to /boot/firmware/config.txt:

dtparam=spi=on

dtoverlay=dwc2,dr_mode=peripheral

cma=96M
dtoverlay=tc358743
dtoverlay=tc358743-audio

Kernel Modules

$ sudo modprobe libcomposite
$ sudo nano /boot/firmware/cmdline.txt
# Add to the end of the single line: modules-load=dwc2,libcomposite

Build Dependencies

• Zig 0.15.2 or later
• pnpm (for building the web frontend)

Building

$ zig build

The binary will be at zig-out/bin/mykvm.

Usage

Usage: mykvm --cert <path> --key <path> [options]

Required:
  -c, --cert <path>         TLS certificate path
  -k, --key <path>          TLS private key path

Options:
  -p, --port <port>         HTTPS server port (default: 8443)
  -l, --listen <address>    Listen address (default: 0.0.0.0)
  -d, --device <path>       Capture device path (default: /dev/video0)
  -e, --encoder <path>      Encoder device path (default: /dev/video11)
  -r, --bitrate <bps>       Encoder bitrate (default: 1000000)
  --no-epaper               Disable e-Paper display
  -h, --help                Show help information

Examples

# Basic usage with self-signed certificate
$ mykvm --cert cert.pem --key key.pem

# Custom port
$ mykvm --cert cert.pem --key key.pem --port 443

# Higher bitrate for better quality
$ mykvm --cert cert.pem --key key.pem --bitrate 2000000

Generating a Self-Signed Certificate

$ openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes

Architecture

┌─────────────┐    HDMI    ┌───────────┐    CSI    ┌─────────────┐
│   Target    │───────────▶│  TC358743 │──────────▶│   Pi Zero   │
│   Machine   │            └───────────┘           │      2W     │
└─────────────┘                                    └──────┬──────┘
       ▲                                                  │
       │ USB HID                                          │ HTTPS/WS
       │                                                  ▼
┌──────┴──────┐                                    ┌─────────────┐
│  USB OTG    │◀───────────────────────────────────│   Browser   │
│  (Keyboard  │                                    │  (WebCodecs)│
│   + Mouse)  │                                    └─────────────┘
└─────────────┘

Video Pipeline

The video pipeline uses zero-copy DMABUF buffers shared between V4L2 capture and the hardware H.264 encoder:

1. TC358743 captures HDMI → /dev/video0 (V4L2 capture)
2. Frames passed via DMABUF to bcm2835-codec → /dev/video11 (V4L2 M2M encoder)
3. H.264 stream sent to browser via WebSocket
4. Browser decodes using WebCodecs (or jMuxer fallback)

USB HID

USB HID gadget is configured via ConfigFS at runtime:

• /dev/hidg0: Boot Protocol keyboard (8-byte reports)
• /dev/hidg1: Absolute positioning mouse (6-byte reports)