KeyCatcher Hardware Bridge

The universal interface for locked-down environments. Type anywhere, from any device, without drivers or software restrictions.

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Overview

KeyCatcher turns a small ESP32 board into a universal keyboard bridge. A Windows or Android client sends text and macros over BLE or UDP. The device replays them as USB or BLE HID keystrokes on any host.

What it is

  • KeyCatcher Server: Firmware for ESP32 that acts as a standard HID keyboard.
  • KeyCatcher Client: Windows and Android applications to manage and send data.

How it works

  1. Client splits text into checksum-verified chunks.
  2. Server acknowledges delivery and requests retries on loss.
  3. Server renders payload as keystrokes with selectable layouts.
  4. Automatic transport switching (BLE/UDP) based on link quality.

Server (ESP32)

  • Input: BLE and UDP.
  • Output: USB HID or BLE HID Keyboard.
  • Auto-reconnect and chunked reliable transport.
  • Web UI for configuration and documentation.

Client (Windows & Android)

  • Unified UI for both platforms.
  • Support for large messages (up to 6KB).
  • Picture-to-Text helper (OCR) for rapid data entry.
  • Configure device identity and network settings.
KeyCatcher App Screenshot

Security

  • BLE Pairing and allow-listing.
  • Pre-shared keys for UDP sessions.
  • Local-first design; no dependency on external clouds.