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Functional description

W-BACnet is designed to be simple to use, in that it requires little intervention from an external CPU.

Commissioning

Commissioning a W-BACnet system is performed in the following steps:

  1. Put the W-BACnet module connected to the BACnet MS/TP Controller/Device into "Commissioning Gateway" mode via the SPI or UART management interfaces.

  2. Put the W-BACnet modules connected to the MS/TP Device devices into "Commissioning Mesh" mode via the SPI or UART management interface.

  3. Devices in mesh commissioning mode will join the gateway node and receive network credentials. In order to determine when this has happened, the COMMISSIONING field/register can be read via the SPI or UART management interfaces. When the value of COMMISSIONING is 1, the mesh node is ready. A mesh node usually takes around one minute to fully join the network, but this process can take longer depending on the physical environment (like walls and radio interference).

  4. Optional: The RS485 bus communication parameters can be configured via the SPI or UART management interface. Any RS485 configuration written to the gateway node acts as the default for all mesh nodes in the network. Mesh nodes with a locally set RS485 configuration will ignore this default. RS485 configuration written to a mesh node will only affect that one mesh node. The RS485 configuration can be written during both the commissioning and secure network states.

  5. Optional: Once all mesh nodes are ready, as indicated by the COMMISSIONING field/register, the system can be validated by having the BACnet MS/TP Controller/Device device poll BACnet MS/TP Device devices as if the BACnet devices were connected by a cable.

  6. Set the W-BACnet module connected to the MS/TP Controller/Device device to "Secure Gateway" mode via the SPI or UART management interface. At this point, the Gateway will broadcast a message to all mesh nodes in the network, instructing all devices to perform a synchronized restart after 10 seconds. After the restart has been performed, the W-BACnet Commissioning Gateway will enter "Secure Gateway" mode, and all connected Commissioning Mesh nodes will enter "Secure Mesh" mode. The commissioning process is now complete. The mesh nodes will search for the gateway again after the synchronized restart, and communicate securely using encryption, until explicitly decommissioned.

Decommissioning

Decommissioning a mesh node from a network can be done by utilizing the DEVICE_RESET field/register using the SPI or UART management interfaces. The node will restart automatically, at which point the device can be commissioned again.

To decommission an entire mesh network at once, put the Secure Gateway into "Gateway Commissioning" mode. The gateway will send a broadcast, instructing currently connected nodes in the network to decommission. In the same manner as described in the Commissioning section, this broadcast also makes connected mesh nodes perform a synchronized restart 10 seconds after receiving the broadcast. After the synchronized restart, each connected mesh node will switch to commissioning mesh mode.

RS485 bus configuration

The writing of RS485 configuration to the W-BACnet device can be done regardless of the current app mode.

An RS485 configuration written to a gateway node applies not only to itself, but also acts as the default for mesh nodes in the network. The default can be overridden, by writing RS485 configurations to mesh nodes individually. Mesh nodes other than the one being written will be unaffected. This feature allows BACnet devices with differing RS485 configuration to communicate in the same BACnet network.

NOTE: Individually written RS485 configurations, called local configurations, are lost on restarts, meaning the default RS485 configuration set on the gateway node will be used instead.

Detection of connected device

A W-BACnet module will listen passively on the bus for activity from connected devices. Once a device has been detected and the module has joined a wireless network, polling activity will begin. The Mesh Module supports a single MS/TP device on the bus and a gateway module can support several MS/TP devices for pre-existing networks. The addresses of detected devices can be accesses through the SPI or UART Interfaces by reading the SERVER_ADDRESSES bits/register.

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