Sensor Beacon Application

A Zephyr application that broadcasts onboard sensor data (accelerometer, temperature, humidity) and battery voltage information via Bluetooth beacon advertisements, with BLE connection support for runtime configuration via AT commands.

This application is designed to be used with the Atmosic DevTools mobile app to monitor sensor data. It also exposes an AT command interface over BLE GATT for runtime device configuration.

Overview

The sensor_beacon application provides sensor data collection and broadcasting via Bluetooth beacon advertisements, together with BLE connection support and an AT command interface for runtime configuration. It uses dual extended advertising sets: a non-connectable set that continuously broadcasts sensor data, and a connectable set that allows a BLE central to connect, authenticate, and issue AT commands over GATT.

Using with Atmosic DevTools App

The sensor_beacon application is designed to work with the Atmosic DevTools mobile app for monitoring sensor data and controlling wake-up.

Monitoring Sensor Data

  1. Open the Atmosic DevTools app

  2. Navigate to APPLICATIONS → BEACON

  3. The app will start scanning for devices

  4. When your sensor beacon device appears, tap MONITOR

  5. The app will display real-time sensor data from the device

Features

  • Sensor Data Collection: Reads temperature, humidity, and 3-axis accelerometer data

  • Battery Monitoring: Monitors VStore and VBatt voltages

  • Bluetooth Beacon Advertising: Broadcasts sensor data using a standardized beacon format

  • BLE Connection Support: Accepts connections on a second advertising set and provides GATT services for AT command transport

  • AT Command Interface: Runtime configuration of device name, advertising interval, and custom advertising data; settings are persisted to NVS flash

  • Periodic Updates: Configurable interval for sensor data updates

  • Power Management: Supports Zephyr power management

  • Comprehensive Testing: Full Ztest test suite included

Architecture

The application follows a modular design with clear separation of functionalities:

sensor_beacon/
├── src/
│   ├── main.c                 # Application entry point; BLE connection callbacks
│   ├── sensor_beacon.c        # Main application logic and sensor loop
│   ├── sensor_interface.c     # Sensor reading with scaling
│   ├── battery_monitor.c      # Battery voltage monitoring
│   ├── beacon_adv.c           # Dual-set Bluetooth advertising (sensor + connection)
│   ├── beacon_adv_at_cmd.c    # AT command extensions with NVS persistence
│   ├── at_gatt.c              # GATT service for AT command transport (TXRX characteristic)
│   ├── at_cmd_manager.c       # AT command routing and unlock state machine
│   └── sensor_data.c          # Periodic sensor data collection
└── tests/                     # Comprehensive test suite

Dual advertising sets (both started at boot):

  • Set 0 — Non-connectable extended advertising (SID 0). Carries the full sensor beacon payload (Eddystone-URL, Manufacturer Data with sensor readings). Interval: 1–1.2 s normal, 100–150 ms fast.

  • Set 1 — Connectable extended advertising (SID 1). Carries only Flags + Complete Name. Used by a BLE central to connect and interact with the GATT-based AT command interface. Interval: slow (BT_GAP_ADV_SLOW_INT_MIN/MAX).

Configuration

Key configuration options in prj.conf:

  • CONFIG_SENSOR_BEACON_UPDATE_INTERVAL: Update interval in centiseconds (default: 100 = 1s)

  • CONFIG_SENSOR_BEACON_FAST_ADV: Enable fast advertising mode for quick device discovery (default: n)

  • CONFIG_BT_EXT_ADV_MAX_ADV_SET: Number of extended advertising sets (default: 2 — one sensor beacon set, one connectable set)

  • CONFIG_ATM_AT_CMD: Enable AT command core framework (default: y)

  • CONFIG_AT_CMD_SET: Enable subsys AT command set (default: y)

  • CONFIG_AT_CMD_LOCK_SET: Enable lock/unlock commands (default: y)

  • CONFIG_SETTINGS / CONFIG_NVS: Persistent storage for device name and user ad data

Beacon Advertising Intervals

The application supports two advertising modes (selected by Kconfig):

  • Normal Mode (Default): 1-1.2 second intervals for optimal power consumption

  • Fast Mode: 100-150ms intervals for quick device discovery

To enable fast mode, set CONFIG_SENSOR_BEACON_FAST_ADV=y in your configuration.

Sensor Data Format

The application uses a standardized sensor data format for client compatibility:

typedef struct {
    uint16_t temp;      // Temperature (scaled by 256)
    uint16_t humidity;  // Humidity (scaled by 256)
    uint16_t x_axis;    // X-axis acceleration (scaled)
    uint16_t y_axis;    // Y-axis acceleration (scaled)
    uint16_t z_axis;    // Z-axis acceleration (scaled)
    float vstore;       // Storage voltage (volts)
    float vbatt;        // Battery voltage (volts)
} __packed sensor_beacon_data_t;

Beacon Advertisement Structure

The sensor beacon advertising set (Set 0, non-connectable) uses the following payload:

  1. Flags: BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR

  2. Complete Name: Device name (runtime-configurable via AT+BLEGAPDEVNAME; persisted to NVS)

  3. Service UUID: Eddystone UUID (0xFEAA)

  4. Service Data: Eddystone-URL pointing to atmosic.com

  5. Manufacturer Data: Atmosic Company ID (0x0A24) + sensor data

The connectable advertising set (Set 1) carries only:

  1. Flags: BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR

  2. Complete Name: Device name

AT Command Interface

The sensor_beacon application includes a BLE GATT-based AT command interface that enables runtime configuration of the device over a Bluetooth LE connection. This feature is enabled by default in the production configuration (prj.conf).

Prerequisites

AT command support requires the following Kconfig options (all enabled by default in prj.conf):

  • CONFIG_ATM_AT_CMD=y — AT command core framework

  • CONFIG_AT_CMD_SET=y — Subsys AT command set

  • CONFIG_AT_CMD_LOCK_SET=y — Lock/unlock command set

  • CONFIG_BT_MAX_CONN=2 — Allows inbound BLE connections for configuration

  • CONFIG_SETTINGS=y / CONFIG_NVS=y — Persistent storage for settings

Note

When CONFIG_BT_MAX_CONN is set to 2, the device advertises as connectable to allow BLE GATT-based configuration in addition to broadcasting beacon data.

GATT Service

AT commands are transported over a custom BLE GATT service. Connect to the sensor beacon device and interact with the TXRX characteristic:

Attribute

Details

Service

custom 128-bit UUID

Characteristic

TXRX (custom 128-bit UUID) Properties: Write + Notify

  • Write the AT command string to the TXRX characteristic to issue a command.

  • Enable notifications on the TXRX characteristic to receive command responses.

Security — Lock/Unlock Mechanism

The device starts in a locked state on every power-on and on every new BLE connection. All configuration commands are rejected while locked. Use AT+SYSUNLOCK to unlock.

For the full command reference see System Commands.

Supported AT Commands

Command Syntax

AT commands follow the standard format:

AT+<COMMAND>=<parameter>

The AT+ prefix is case-insensitive.

Command Reference

AT+SYSLOCK

Locks the AT command channel or queries the current lock state. Lock-exempt — can be sent at any time regardless of lock state.

AT+SYSLOCK=ON       # Lock the channel
AT+SYSLOCK?         # Query lock state

Responses: OK — locked; +SYSLOCK:ON / +SYSLOCK:OFF — query result.

See System Commands for full reference.

AT+SYSUNLOCK

Unlocks the AT command channel. Must be sent before any configuration command. Lock-exempt.

AT+SYSUNLOCK=<key>

Responses: OK — unlocked; ERROR:144 — wrong key.

Note

Default key: atm1atm123 (CONFIG_AT_CMD_SYSUNLOCKKEY_VALUE).

See System Commands for full reference.

AT+BLEGAPDEVNAME

Sets or queries the BLE GAP device name. The new name is immediately reflected in the advertisement and persisted to NVS flash so it survives reboot.

AT+BLEGAPDEVNAME=<name>     # Set device name
AT+BLEGAPDEVNAME?           # Query current device name

Parameter

Description

<name>

New device name string (1 to 22 characters)

Requires: Device must be unlocked (AT+SYSUNLOCK first).

Example:

AT+BLEGAPDEVNAME=MySensorTag

Responses:

  • OK — Device name updated; advertising restarted with the new name

  • +BLEGAPDEVNAME:<name> — Current device name (query)

  • ERROR — Device locked, name too long, or write failure

Note

The default device name is Atmosic Sensor Beacon. Maximum length is set by CONFIG_BT_DEVICE_NAME_MAX (default: 22 characters).

See BLE Peripheral Commands for full reference.

AT+BLEADVLEGACYPARM

Sets the legacy advertising parameters. Changes take effect immediately.

AT+BLEADVLEGACYPARM=<idx>,<intv_min>,<intv_max>,<duration>

Requires: Device must be unlocked (AT+SYSUNLOCK first).

Examples:

AT+BLEADVLEGACYPARM=0,1600,1600,0    # 1 second interval, indefinite
AT+BLEADVLEGACYPARM=0,400,400,0      # 250 ms interval, indefinite
AT+BLEADVLEGACYPARM=0,3200,3200,0    # 2 second interval, indefinite

Response:

  • OK — Parameters updated; advertising restarted

  • ERROR — Device locked, index invalid, or value out of range

See BLE Peripheral Commands for full reference.

AT+SYSRESET

Resets the device. Warm reset (0) or cold reset (1).

AT+SYSRESET=<type>

Parameter

Description

<type>

0 = warm reset, 1 = cold reset

Requires: Device must be unlocked (AT+SYSUNLOCK first).

Example:

AT+SYSRESET=1

Response: The device resets immediately; no response is returned to the client.

See System Commands for full reference.

Persistent Storage

The following settings survive reboot (saved to NVS flash):

Typical Usage Sequence

# 1. Connect to the device over BLE
# 2. Enable GATT notifications on the TXRX characteristic
# 3. Unlock the device
AT+SYSUNLOCK=atm1atm123               → OK

# 4. Query lock state
AT+SYSLOCK?                           → +SYSLOCK:OFF

# 5. Change the device name
AT+BLEGAPDEVNAME=MySensorTag          → OK

# 6. Set advertising interval to 2 seconds
AT+BLEADVLEGACYPARM=0,3200,3200,0     → OK

# 7. Reset to verify persisted settings
AT+SYSRESET=1                         (device resets; reconnect to verify)

Building and Running

This application is built from openair/applications/sensor_beacon.

Production Build (Default)

Optimized for power consumption, performance, and minimal logging:

west build -p always -b <BOARD> openair/applications/sensor_beacon --sysbuild -T applications.sensor_beacon.atm

Production Build with MCUboot + Serial DFU

Enables MCUboot and supports firmware upgrades over UART:

west build -p always -b <BOARD>@mcuboot openair/applications/sensor_beacon --sysbuild -T applications.sensor_beacon.atm.mcuboot.dfu

Debug Build

Enhanced logging and debugging aids for development:

west build -p always -b <BOARD> openair/applications/sensor_beacon --sysbuild -T applications.sensor_beacon.atm -DFILE_SUFFIX=debug

Example for ATMEVK-3430e-YQN-5:

Production:

west build -p always -b ATMEVK-3430e-YQN-5 openair/applications/sensor_beacon --sysbuild -T applications.sensor_beacon.atm

Debug:

west build -p always -b ATMEVK-3430e-YQN-5 openair/applications/sensor_beacon --sysbuild -T applications.sensor_beacon.atm -DFILE_SUFFIX=debug

Programming

To flash the built images:

west flash --no-rebuild -d build --verify --device <DEVICE_ID> --jlink --fast_load

Example:

west flash --no-rebuild -d build --verify --device 000900066361 --jlink --fast_load

Configuration Differences

The debug and production builds have identical functionality - they differ only in logging verbosity:

Feature

Production Build

Debug Build

Logging Level

Warning/Error only (level 2)

Debug/Verbose (level 4)

ADC Logging

Error level only

Debug level

Sensor Logging

Warning level only

Debug level

Function Names

Not logged

Logged with debug messages

All Other Settings

Identical

Identical

Note

Both configurations maintain the same:

  • Update intervals (1 second)

  • Beacon advertising intervals (1-1.2s normal, 100-150ms fast)

  • Power management settings

  • Stack sizes

  • Watchdog configuration

  • BLE advertising behavior (dual advertising sets)

  • Sensor functionality

Testing

To build and run the test suite:

west build -p always -b <BOARD> openair/applications/sensor_beacon/tests --sysbuild
west flash --no-rebuild -d build --verify --device <DEVICE_ID> --jlink --fast_load

Example:

west build -p always -b ATMEVK-3430e-YQN-5 openair/applications/sensor_beacon/tests --sysbuild
west flash --no-rebuild -d build --verify --device 000900066361 --jlink --fast_load

The test suite includes:

  • Sensor interface validation

  • Battery monitoring tests

  • Beacon advertising tests (dual advertising sets, device name updates)

  • AT command interface tests (lock/unlock, device name, reset)

  • Data collection and sensor integration tests

Power Management

The application supports Zephyr power management:

  • Periodic sensor readings with configurable intervals

  • Automatic sleep between operations

  • Watchdog integration for reliability

LED and Button Functionality

The sensor_beacon application provides platform-specific LED indication and button control functionality to support different hardware configurations.

LED Indications

The application supports three types of LED indications:

  1. Power ON Indication (Tag designs only)

    • Primary LED blinks 3 times at 0.5s interval

    • Shown when device transitions from OFF to ON state via button press

    • Only available when CONFIG_SENSOR_BEACON_BUTTON_POWER_CONTROL is enabled

  2. Power OFF Indication (Tag designs only)

    • Secondary LED blinks 3 times at 0.5s interval

    • Shown when device transitions from ON to OFF state via button press

    • Only available when CONFIG_SENSOR_BEACON_BUTTON_POWER_CONTROL is enabled

  3. Beacon Status Indication (All platforms)

    • Primary LED blinks once for 0.1s

    • Shown every 10 beacon data updates to indicate active beaconing

    • Available on all platforms with LED support

Button Functionality

Button behavior varies by platform configuration:

Tag Designs (Button Power Control Enabled)

When CONFIG_SENSOR_BEACON_BUTTON_POWER_CONTROL is enabled (default for ATMBTCSTAG-3405):

  1. Initial State: Device starts in SoC_off mode when battery is inserted

  2. Turn Device ON: Press button for 2 seconds to bring the device out of soc-off mode

    • Device exits SoC_off mode

    • LED blinks 3 times at 0.5s interval

    • Device starts beaconing

  3. During Beaconing: LED blinks (0.1s on/off) every 10 beacon data updates

  4. Turn Device OFF: Press button for 2 seconds while beaconing

    • LED blinks 3 times at 0.5s interval

    • Device enters SoC_off mode

EVK Boards (Immediate Beaconing Mode)

When CONFIG_SENSOR_BEACON_BUTTON_POWER_CONTROL is disabled (default for EVK boards):

  1. Initial State: Device immediately enters beaconing mode after power on

  2. No ON/OFF Control: Button does not control device power state

  3. During Beaconing: LED blinks (0.1s on/off) every 10 beacon data updates

Supported Boards

The sensor_beacon application has been tested and verified on the following platforms:

ATM34 Platforms

  • ATMBTCSTAG-3405 - ATM34 Tag Reference Design

    • Button power control enabled by default

    • Dual LED support

    • Sensors: ENS210 (Temp/Humidity), LIS3DH (Accelerometer)

    • Optimized for battery-powered operation with SoC_off support

  • ATMEVK-3430e-YQN-5 - ATM34 Evaluation Kit

  • ATMEVK-3405-PBV-5 - ATM34 Evaluation Kit

  • ATMEVK-3405-PQK-5 - ATM34 Evaluation Kit

  • ATMEVK-3405-WQK-5 - ATM34 Evaluation Kit

  • ATMEVK-3405-YBV-5 - ATM34 Evaluation Kit

    • Immediate beaconing mode (no button power control)

    • LED support for beacon status indication

    • Sensors: ENS210 (Temp/Humidity), LIS2DH12 (Accelerometer)

    • Suitable for development and testing

ATM33 Platforms

  • ATMEVK-3330e-QN-6 - ATM33 Evaluation Kit (Planned)

  • ATMEVK-3330e-QN-7 - ATM33 Evaluation Kit (Planned)

    • Immediate beaconing mode (no button power control)

    • LED support for beacon status indication

    • Sensors: ENS210 (Temp/Humidity), LIS2DH12 (Accelerometer)

    • Suitable for development and testing

All supported platforms use the same sensor set for consistent data collection across different hardware configurations.

Compatibility

  • Data Format: Uses standardized sensor beacon data format

  • Advertisement Structure: Standard Bluetooth beacon format with manufacturer data

  • Passive Observers: Compatible with any BLE scanner or beacon monitoring application (Atmosic DevTools, etc.) — no connection required to receive sensor data

  • BLE Centrals: Can connect to the device, authenticate via AT+SYSUNLOCK, and issue configuration commands over the GATT TXRX characteristic

Dependencies

Required Hardware:

  • ENS210 temperature/humidity sensor

  • LIS2DH accelerometer

Ensure that the appropriate jumper (JP25) is installed to enable the sensor subsystem. Refer to the EVK’s user guide for additional details.