- After gateway receives a list of nodes from the backend and there’s an unpaired sensor, it sends the request to GGRA to connect to this node along with the payload (desired configuration)
- When they are connected, the Bluetooth characteristics are being registered as REST services in Service Registry
- The Authorization and Orchestration rules are dynamically set for the data provisioning service, and it’s orchestrated to the gateway’s main service
- The data are passed to the backend for further processing, or are available on the gateway
Meet GAP GATT REST API: Automated Sensor Onboarding Made Possible with Custom Tool for BLE Data Provisioning
The DAC.digital team faced a critical challenge: onboarding sensors automatically across multiple local clouds. Their environments relied on dense networks of BLE sensors, and manually connecting each node was impractical, time-consuming, and error-prone. They needed a way to coordinate these networks, so that every device could be seamlessly integrated, configured, and ready to deliver data at scale.
BLE devices were not designed to operate within modern service-oriented architectures
The root of the problem lay in the nature of BLE itself. Operating within service-oriented architectures was never part of BLE devices’ design. BLE was built for low-power, point-to-point or small mesh communication between devices such as sensors, wearables, or peripherals. Its protocols focus on direct device-to-device connections, minimal energy consumption, and lightweight data exchange, but lack mechanisms for orchestration, discovery, or scalable fleet management. As a result, gateways could detect sensors, but they couldn’t orchestrate or manage them at scale. Manual configuration of each node was slow, error-prone, and unsuitable for large sensor fleets.
The team decided to translate BLE interactions into the language of service-oriented architectures
To overcome these limitations, the team realized they needed a way to bridge low-level BLE communication with Arrowhead’s service-oriented ecosystem. This meant building a configuration toolchain that could automatically provision and manage new sensors, regardless of fleet size or deployment environment. By translating BLE interactions, each sensor could now behave like a REST-enabled service, fully discoverable, configurable, and orchestratable within Arrowhead.
This is how the GAP GATT REST API came to be
The solution was the GAP GATT REST API, a standards-compliant translator that integrates BLE devices into the Arrowhead ecosystem. It allows gateways to:
- Automatically discover and connect to new BLE sensors
- Expose sensor services and characteristics as REST endpoints
- Apply authorization and orchestration rules dynamically
- Manage fleets at scale, without manual configuration or specialized BLE knowledge
With the GAP GATT REST API, BLE nodes that were once isolated and manual to manage now operate as fully orchestrated, service-oriented resources, enabling automated onboarding and fleet-wide management across multiple local clouds.
The GAP GATT REST API is built on two core Bluetooth profiles
Together the profiles enable full automation and integration of BLE sensors.
1. Generic Access Profile (GAP)
- Node discovery: it scans BLE sensors both passively and actively
- Automatic connection: it connects to unpaired sensors without manual intervention
- Protocol translation: it maps HTTP GET requests to BLE READ operations and PUT requests to BLE WRITE operations
- Real-time updates: it streams notifications and indications to Arrowhead via EventSource
2. Generic Attribute Profile (GATT)
- Service discovery: it identifies available services and characteristics by UUID
- Data handling: it reads and writes characteristics and descriptors
- Subscriptions: it supports notifications and indications for real-time sensor updates
- Server-side management: it handles updates and event-driven communication on the sensor itself
By combining GAP and GATT, the API transforms BLE devices into fully managed, REST-compliant resources. Gateways can now discover, configure, and orchestrate sensors automatically, eliminating the need for manual intervention or specialized BLE expertise.
State of the art.
New developments and recent trends in wireless sensor networking technologies have sparked the creation of inexpensive, low-power, multipurpose sensor nodes. Data processing and environment sensing are made possible by sensor nodes. Different surroundings may be monitored with the use of sensors that can detect volatile compounds, temperature, and humidity. They can communicate via networks with other sensor devices and share data with outside users.
The evolution of the Web as we know it has been influenced by the Representational State Transfer (REST) architectural style, which outlines a set of guidelines for the design of networked hypermedia systems. RESTful Web services are web services that adhere to the REST architectural style, and REST APIs are the programmatic interfaces for these services. The architectural decisions made by the Web to support the scalability and stability of networked, resource-oriented systems based on HTTP have greatly influenced the design concepts for REST APIs. The core principles are: Resource addressability, resource representations, uniform interface, statelessness, hypermedia as the engine state.
The use of GATT REST API and GAP REST API for Bluetooth low energy devices was introduced back in 2013. Since there they have been seen in several applications. GAP defines the general topology of the BLE network stack. GATT describes in detail how attributes (data) are transferred once devices have a dedicated connection.
In this context, one of the main motivations of this solution was that Legacy data exchange technologies are not supported by modern SOA/microservices architectures. Moreover, the deployment of complex sensor networks, their management, diagnosis, decommissioning, and evolution of the sensor network, required specialised knowledge and tools. Hence to overcome this limitation, an onboarding tool was developed, of which GAP GATT REST API was a part.
The Solution: How does it work?
The tool is implemented according to Bluetooth Special Interest Group (Bluetooth SIG) specifications (GAP REST API V10r01 and GATT REST API V10r01) and is a natural proxy/translator between BLE communication interfaces and REST API (used by Eclipse Arrowhead).
Arrowhead Compatibiliy.
To make the tool compatible with Arrowhead, a specially designed Attribute Table is used to differentiate measurements (with value characteristics) and metadata about the device. Both measurement service and metadata service are registered in Arrowhead Service Registry as soon as they are connected to the gateway (in UC11 there’s a tool responsible for automated connection with the BLE nodes). At the same time, the authorization and orchestration rules are created, and the gateway that requested the connection can consume the incoming data from the provider.