example/

device-simple

The included device-simple example device service demonstrates basic usage of device-sdk-go.

Protocol Driver

To make a functional Device Service, developers must implement the ProtocolDriver interface. ProtocolDriver interface provides abstraction logic of how to interact with Device through specific protocol. See simpledriver.go for example.

Protocol Discovery

Some device protocols allow for devices to be discovered automatically. A Device Service may include a capability for discovering devices and creating the corresponding Device objects within EdgeX.

To enable device discovery, developers need to implement the ProtocolDiscovery interface. The ProtocolDiscovery interface defines a single Discover method which is used to trigger protocol-specific device discovery. Any devices found as a result of discovery being triggered are returned to the SDK via a go channel, passed to the implementation as a parameter during Initialization. New discovery attempts may be started as soon as a slice of devices is submitted, so in oreder to avoid the service being congested by concurrent discovery.

The SDK will then filter these devices against pre-defined acceptance criteria (i.e. Provision Watchers), and add any devices which match (excluding existing devices).

A Provision Watcher contains the following fields:

Identifiers: A set of name-value pairs against which a new device's ProtocolProperties are matched
BlockingIdentifiers: An additional set of name-value pairs which if matched, will block the addition of a newly discovered device.
Profile: The name of a DeviceProfile which should be assigned to new devices which meet the given criteria
AdminState: The initial Administrative State for new devices which meet the given criteria

A candidate new device passes a ProvisionWatcher if all of the Identifiers match, and none of the Blocking Identifiers match. For devices with multiple Device.Protocols, each Device.Protocol is considered separately. A match on any of the protocols results in the device being added.

Finally, A boolean configuration value Device/Discovery/Enabled defaults to false. If it is set true, and the DS implementation supports discovery, discovery is enabled. Dynamic Device Discovery is triggered either by internal timer(see Device/Discovery/Interval in configuration.toml) or by a call to the device service's /discovery REST endpoint.

The following steps show how to trigger discovery on device-simple:

1. Set Device/Discovery/Enabled to true in configuration file
2. Post the provided provisionwatcher into core-metadata endpoint: http://edgex-core-metadata:48081/api/v1/provisionwatcher
3. Trigger discovery by sending POST request to DS endpoint: http://edgex-device-simple:49990/api/v1/discovery
4. Simple-Device02 will be discovered and added to EdgeX.