GhostLever is a USB device for locked-down corporate PCs where installing software, browser extensions, drivers, or background services is blocked. Built around two RP2040 boards, it sits between a USB input device and a computer, listening for trigger text and types expansions when it detects it. It is like a cross between a macro keypad and text-expansion software with a real time clock to allow generating date functions.

Configuration is handled by the browser-based GhostLever configurator in this repository. Rules are saved on the primary board, so they continue to work after the configurator is disconnected.

Breadboard prototype: the computer-facing primary RP2040 is on the left, the USB-host bridge is on the right, and the DS3231 real-time clock module is at the bottom. Jumper colors are only illustrative—follow the pin table below.

Why a hardware solution?

GhostLever presents itself to the computer as a standard USB HID keyboard. Its rules run on the hardware, not on the corporate PC. A device can therefore be configured on a permitted system and then provide approved keyboard automation without an installed application or background process on the managed workstation.

This design is intended for authorized productivity and accessibility workflows. It does not override endpoint controls, and an organization may restrict external HID devices. Obtain approval from the employer or IT/security team before connecting GhostLever to a managed computer, and do not store passwords, access tokens, or other secrets in expansion rules.

Features

• Typed triggers that expand into reusable text or multi-step actions
• Configurable actions for a 19-key numeric keypad
• Keyboard shortcuts and inline HID key combinations
• Date, time, and custom placeholders backed by a DS3231 real-time clock
• Pass-through for unassigned keyboard/keypad input
• Consumer-control media keys and standard mouse pass-through
• Browser configuration over USB serial using Chrome or Edge
• Up to 128 active rules within the 32 KB configuration limit

Hardware

The pictured two-board build uses:

• Two RP2040-Zero-compatible boards
• One DS3231 real-time clock module
• One breadboard and jumper wires
• One USB host/OTG adapter that supplies VBUS to the attached input device
• USB cables for the computer and input-device connections
• A USB keyboard, keypad, mouse, or compatible receiver

Wiring

Primary board to USB-host bridge

Primary board	Bridge board	Purpose
GPIO4 (TX)	GPIO5 (RX)	UART data to bridge
GPIO5 (RX)	GPIO4 (TX)	UART data from bridge
GND	GND	Common ground
Native USB-C	Computer	USB HID and configurator connection
—	Native USB-C	USB host connection to the input device

The bridge USB-C connector is the downstream host port. Use an OTG/host connection that provides VBUS to the keyboard, keypad, mouse, or receiver.

Primary board to DS3231

Primary board	DS3231	Purpose
GPIO6	SDA	I2C data
GPIO7	SCL	I2C clock
3V3	VCC	RTC power
GND	GND	RTC ground

Use 3.3 V for the RTC module so any onboard I2C pull-ups do not raise the RP2040 GPIO lines above their safe voltage.

Firmware setup

The Arduino environment requires:

• Raspberry Pi Pico/RP2040 board package
• Adafruit TinyUSB Library
• Adafruit NeoPixel
• Pico-PIO-USB
• ArduinoJson 7

1. Flash the bridge board

Open firmware/UsbUart_Bridge/UsbUart_Bridge.ino and flash it to the RP2040 board connected to the input device. Select Adafruit TinyUSB Host (native) as the USB stack.

2. Flash the primary board

Open firmware/RTC_Setup/RTC_Setup.ino and flash it to the computer-facing RP2040 board. The current firmware is verified with these settings:

• Board profile: Waveshare RP2040 Zero
• USB stack: Adafruit TinyUSB
• Flash size: 2 MB with a LittleFS partition (256 KB recommended)
• CPU speed: 240 MHz

The 240 MHz setting is an RP2040 overclock used by the PIO USB fallback path; qualify it on the specific hardware before relying on the device in a critical workflow.

3. Configure GhostLever

1. Open index.html from an HTTPS site or serve the repository on localhost.
2. Use Chrome or Edge and select Connect Device.
3. Choose the GhostLever serial port.
4. Create typed expansions or keypad actions, then write the configuration to the device.
5. Use the Date/Time page to synchronize the DS3231 clock when needed.

Web Serial requires a secure context, so opening index.html directly as a local file may not provide device access.

Status LED

The onboard RGB LED reports the general device state:

• Red: initialization failed or no active input path
• Blue: USB host is ready and waiting for an input device
• Green: an input device is connected and active

Repository layout

Path	Contents
index.html	GhostLever browser configurator
firmware/RTC_Setup	Primary device firmware and detailed behavior
firmware/UsbUart_Bridge	USB-host bridge firmware
firmware/third_party/Pico_PIO_USB	Vendored PIO USB dependency and project patch notes
expansion-sets	Installable shared expansion sets
tools	Serial and stability diagnostics

For lower-level firmware behavior, protocol details, and the original single-board PIO USB wiring, see the RTC_Setup firmware notes.