lima-node

L.I.M.A. > (Local Integrity Multi-modal Architecture) The lima-node is a low-power kinetic / physical intrusion detection system. Utilizing a Zephyr RTOS micro-kernel on the nRF52840, the system implements hardware-accelerated motion discrimination via an MPU6050 IMU. This node sends telemetry through an encrypted BLE-to-MQTT gateway, providing a resilient audit trail for physical access events.

Hardware Specification

• Edge Node: Nordic Semiconductor nRF52840-DK (Cortex-M4F)
• Gateway: Raspberry Pi Zero (Nano) running a hardened Linux stack
• Connectivity: Bluetooth Low Energy (BLE) 5.0 with Coded PHY support for extended range

System Overview

1. The LIMA Node (The "Edge")

• Hardware: nRF52840 + MPU6050 + Barometric Sensor.
• Software: Zephyr RTOS + CryptoCell-310.

◇ Function: Detects "Integrity Events" (Door open, Case tamper) and signs the alert.

2. The LIMA Gateway (The "Bridge")

• Hardware: Raspberry Pi or an nRF7002 (Wi-Fi) development kit.
• Software: MQTT Broker + Python/Node.js Logic.

◇ Function: Translates the local BLE/Thread signal into a phone notification (via Pushbullet or Pushover).

Bringing Up the L.I.M.A. Node

This project uses a Local Manifest topology. Follow these steps to initialize the workspace and install the necessary dependencies for the nRF52840.

1. Prerequisite: Python Environment We recommend using a virtual environment to avoid dependency drift.

Create and activate a clean environment

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

Install West (Zephyr's meta-tool)

pip install west

2. Initialize the Workspace The west.yml in this repository acts as the master blueprint for the entire SDK. Bash

Initialize the workspace using this repo as the local manifest

west init -l lima-node

Pull the Nordic Connect SDK (NCS), Zephyr, and HAL modules

west update

3. Install SDK Requirements Once the modules are downloaded, install the specific toolchain requirements:

pip install -r zephyr/scripts/requirements.txt
pip install -r nrf/scripts/requirements.txt
pip install -r bootloader/mcuboot/scripts/requirements.txt

4. Build & Verify

Test the toolchain by building the firmware for the nRF52840 MDK Dongle:

west build -b nrf52840_mdk lima-node/firmware

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folder layout:

├── src/
│   ├── firmware/       # nRF52840 C++/Arduino code
│   └── gateway/        # Python bridge for RPi
├── docs/               # The "Senior Engineer" stuff
│   ├── architecture/   # Diagrams and Schematics
│   └── analysis/       # Power and Threat models
├── tests/              # Validation scripts
├── LICENSE
└── README.md