MDS over HID Application

Zephyr RTOS application implementing the Memfault Diagnostic Service (MDS) protocol over USB HID for nRF52840.

Features

• USB HID interface for MDS protocol communication
• Memfault diagnostics data collection and streaming
• Configurable heartbeat metrics (10s for testing, 1h default for production)
• Support for all MDS protocol reports:
  • Supported Features (0x01)
  • Device Identifier (0x02)
  • Data URI (0x03)
  • Authorization (0x04)
  • Stream Control (0x05)
  • Stream Data (0x06)

Hardware

• Board: nRF52840 DK (nrf52840dk/nrf52840)
• USB: VID 0x2fe3 (Zephyr Project), PID 0x0007

Prerequisites

• Python 3.10 or newer
• Zephyr SDK installed
• nRF52840 DK hardware

Setup

1. Clone the Repository

git clone <repository-url>
cd mds-over-hid-app

2. Create Python Virtual Environment

python3 -m venv .venv
source .venv/bin/activate

3. Install West

pip install west

4. Initialize West Workspace

This pulls Zephyr RTOS, nRF SDK, and all dependencies (this may take several minutes):

west init -l app
west update

5. Install Python Dependencies

pip install -r zephyr/scripts/requirements.txt

6. Configure Memfault

Copy the template configuration and add your Memfault project key:

cp app/prj.conf.template app/prj.conf
# Edit app/prj.conf and replace YOUR_PROJECT_KEY_HERE with your actual key

Get your project key from https://app.memfault.com/ → Settings → General

7. Build

cd app
west build -b nrf52840dk/nrf52840

8. Flash

Connect your nRF52840 DK via USB and flash:

west flash

Configuration

Key configuration options in app/prj.conf:

• CONFIG_MEMFAULT_NCS_PROJECT_KEY: Your Memfault project key (required)
• CONFIG_MEMFAULT_NCS_DEVICE_ID: Unique device identifier
• CONFIG_MEMFAULT_METRICS_HEARTBEAT_INTERVAL_SECS: Metrics collection interval (10s for testing)

Protocol

This device implements the MDS protocol over USB HID. The host can:

1. Query device information via Feature Reports (IDs 1-4)
2. Enable/disable streaming via Stream Control (ID 5)
3. Receive diagnostic data chunks via Stream Data (ID 6)

Development

The application uses Memfault SDK integration for NCS. Diagnostic data is automatically collected and queued for transmission when streaming is enabled by the host.