Device Firmware

Project Overview

This project implements the firmware for a cellular-connected package device. The device is designed to detect if a package has been opened and immediately reports via an NB-IoT cellular connection.

The firmware is built on the nRF Connect SDK (Zephyr RTOS) and runs on the Nordic nRF9160 SiP. It is optimized for ultra-low power consumption, remaining in a deep sleep state until it needs to perform its critical function.

Key Features

• Opening Detection: Uses a VEML6035 Ambient Light Sensor to detect opening.
• Instant Alerting: Connects to an NB-IoT network to transmit an alert payload.
• Ultra-Low Power: Operates in System OFF mode (~shutdown) to maximize battery life, waking only on specific events.
• Robust State Machine: clearly defined lifecycle (Provisioning -> Arming -> Monitoring -> Triggered).
• Double-Tap Reset: Hidden feature to factory reset the device for re-use.

Hardware Requirements

To run this firmware, you need the following hardware:

1. MCU/Modem: Nordic Semiconductor nRF9160 SiP.
2. PMIC: Nordic NPM1300 Power Management IC.
3. Sensor: Vishay VEML6035 Ambient Light Sensor (connected via I2C).
4. Antenna: Antenna forLTE-M/NB-IoT bands.
5. SIM Card: An active iBasis or other compatible NB-IoT/LTE-M SIM card.

Software Architecture

The core logic is driven by a Finite State Machine (FSM) implemented in src/app/fsm.c.

Device Lifecycle

1. PROVISIONING (STATE_PROVISIONING): The initial state after first boot. The device prepares itself for deployment.
2. ARMING (STATE_ARMING): The device waits for a sustained period of darkness (2 minutes by default) to confirm it is inside the package.
3. MONITORING (STATE_MONITORING): The device is "Armed".
   • It configures the light sensor to fire a hardware interrupt upon detecting light.
   • It enters System OFF (Deep Sleep). The CPU is off.
4. TRIGGERED (STATE_TRIGGERED): Wakes up immediately when the sensor interrupt fires (package opened).
5. TRANSMISSION (STATE_TRANSMISSION):
   • Initializes the LTE Modem.
   • Connects to the server
   • Sends a UDP packet indicating the opening.
   • Retries up to 3 times if transmission fails.
6. TERMINATED (STATE_TERMINATED): Final state. The device shuts down sensors and modem and enters permanent deep sleep to save power.