Software

1. Public Interface of the Sensor Ring Library

1.1 Measurement Interface

The public interface has two measurement related components:

• The MeasurementManager:
  This class executes the measurements, collects them and distributes them to all registered subscribers. It is responsible for the timing of the measurement process. The measurements can either be run asynchronously in a separate thread with the startMeasuring() and stopMeasuring() methods, or in the users thread by repeatedly calling the measureSome() method.
  Clients subscribe to measurements via subscribeToDeviceGroup() and to state changes via subscribeToStateChanges(). Each call returns a Subscription object — the callback stays active for as long as the Subscription is alive.
• The ManagerParams
  This is the parameter set that configures the system. The ManagerParams are a cascaded structure, that represents the topology of the system as shown in the diagram below..

1.2 Logger Interface

In addition to the measurement related interface the library provides a logger interface:

• The Logger
  The Logger is a singleton that collects all debug, info and error messages that are raised internally. Clients subscribe to log output via Logger::getInstance()->subscribe(), which returns a Subscription object.
  It is recommended to subscribe to the Logger before creating other library objects so that messages emitted during initialization are not lost (see the Examples section for details).

2. Topology of the System

The EduArt Sensor Ring is a system that collects and combines measurements from multiple individual sensors. The individual sensors are daisy chained together in series and share a communication interface and a power supply. The chain of sensor is terminated by a master device at one end e.g. a Raspberry Pi or a CAN to USB converter. It is possible to use multiple communication interfaces to distribute the sensor data and enable the use of more sensors simultaneously. The following class diagram illustrates the topology and the reflection of the hardware layers in the library.

3. Sensor Ring Factory

The SensorRingFactory is the primary way to create a SensorRing instance. It handles hardware discovery, board validation and device instantiation in a single build() call.

3.1 Basic Usage

The minimal workflow is:

1. Create a factory instance
2. Register communication interfaces with addInterface()
3. Optionally declare expected boards with expectBoard()
4. Call build() to enumerate hardware and construct the SensorRing

ring::SensorRingFactory factory;
factory.addInterface(interface);
auto sensor_ring = factory.build(ring::ValidationMode::Relaxed);

The returned SensorRing is passed to the MeasurementManager as before:

manager::ManagerParams params;
auto manager = std::make_unique<manager::MeasurementManager>(params, std::move(sensor_ring));

3.2 Validation Modes

The build() method accepts a ValidationMode that controls how expectations are matched against discovered hardware.

Mode	Behaviour
Strict	Expectations are matched 1:1 by index against discovered boards. Any mismatch in board type, device type or board count returns nullptr.
Relaxed	For each expectation the factory searches all unclaimed boards for the first compatible one. Boards that are not claimed by any expectation remain unconfigured. Mismatches are logged as warnings.

In strict mode the order and count of expectBoard() calls must match the physical bus exactly. In relaxed mode the factory finds compatible boards regardless of their position on the bus.

3.3 Configuring Board Expectations

Auto-discovery (no expectations): every board found on the bus is used with default configuration.

factory.addInterface(interface);
auto sensor_ring = factory.build(ring::ValidationMode::Relaxed);

Board type constraint: only boards of the specified type are accepted.

factory.expectBoard({ device::SensorBoardType::Headlight });

Explicit device params: only the specified device types are instantiated on the matched board.

factory.expectBoard({}, { device::HTPA32_Params{} });

Default device params: applied to every device of that type when no explicit params are given.

factory.setDefaultDeviceParams(device::VL53L8CX_Params{ .resolution = 4 });

3.4 Enumeration and Topology

The factory can enumerate hardware without building a SensorRing:

auto results = factory.enumerate();
std::cout << factory.printTopology();

The EnumerationMap returned by enumerate() or getLatestEnumerationResult() maps each ComInterfaceID to a vector of EnumerationInformation structs that report board type, connection state, configuration state and available device types.

4. Input Parameters

The ManagerParams configure the runtime behaviour of the MeasurementManager. They are passed as constructor argument and cannot be changed after instantiation.

Parameter	Description
timeout	Duration after which the manager shuts down automatically
enable_brs	Enable CAN FD bit rate switching
repair_errors	Attempt automatic error recovery
frequency_tof_hz	Target frequency for ToF measurements
frequency_thermal_hz	Target frequency for thermal measurements

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