Register Access

Overview

In addition to our message based approach, we have added functionality to offer a generic implementation for register based access. While this has been possible for a long time in BlueRange Mesh by implementing handlers for component_act and component_sense messages, this drastically reduces the implementation effort. If you have knowledge of the modbus protocol, you will be already be familiar with the basic concept.

Registers can be read or written by specyfing the moduleId, a component and the register number. Each module can make use of a full range of ~65k registers for each of the ~65k components. While the module id defines the functionality, the component is typically used to specify a device instance. For example, imagine you have a set of luminaires connected to your controller and each luminaire offers the exact same functionality.

The register handler does not yet offer automatic persistance of configuration registers. This will be added in the future.

In contrast to Modbus, we have decided to offer a simplified and more up-to-date implementation. The main differences are:

  • A register has a minimum size of 1 byte and can have an arbitrary length depending on the data type. Typical sizes are 1 byte for an 8 bit integer, 2 bytes for u16, 4 bytes for u32.

  • The data alignment is little endian by default as this is the default for the BlueRange Mesh implementation.

  • The register range always starts with index 0 and the register should be numbered register 0 to avoid off-by-one issues.

  • Readable and writable registers are available in a single adress range, unlike Modbus where this can very between implementations.

Implementation Guide

Register Ranges

The implementation should adhere to the following convention:

  • Register 0 …​ 9999: Information Registers provide read-only data to offer capabilities such as device serial, number of lightheads, etc, …​.

  • Register 10000 …​ 19999: Configuration Registers are readable/writable registers to modify the functionality of the device. They can be persisted by the device.

  • Register 20000 …​ 29999: Control Registers are readable/writable register, used to actuate the device. For example, turn on a light, set a motor position, etc,…​.

  • Register 30000 …​ 39999: Data Registers are read-only registers used to provide data such as sensor measurements, e.g. the ambient light level, state of the implementation, etc,…​