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Functional description

W-BACnet is designed to be simple to use, requiring little control from an external CPU.

Commissioning

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

  • Set the W-BACnet module connected to the MS/TP device/controller device to the "Commissioning Gateway" application mode via the SPI interface.

  • Set the W-BACnet modules connected to the MS/TP devices to the "Commissioning Mesh" application mode via the SPI interface.

  • Mesh nodes will join the gateway node and receive configuration. The mesh nodes can be polled via the SPI interface by reading the STATUS register and checking the COMMISSIONING bit. Once the bit reads as 1 the node is ready. A node takes approximately one minute to fully join the network

  • (Optional) UART configuration can be written to the gateway node via the SPI interface at this point. Any UART configuration written to the gateway node acts as the default UART settings for all nodes in the network and will apply to all mesh nodes connected to the gateway. UART configuration written to a mesh node will only affect that specific node.

  • (Optional) Once all mesh nodes are ready, as indicated by the COMMISSIONING bit, the system can be tested with BACnet traffic, the BACnet MS/TP device can poll other MS/TP devices on the network and receive responses.

  • Set the W-BACnet module connected to the MS/TP device/controller to the "Secure Gateway" application mode via the SPI interface. All nodes on the network will perform a synchronized restart in 10 seconds, where the node connected to the MS/TP device/controller will enter "Secure Gateway" mode while all nodes connected to the other MS/TP devices will enter "Secure Mesh" mode.

  • Once the synchronized restart is completed the commissioning process is complete!

  • If no UART configuration was written to the gateway node previously, it must be written after the commissioning process.

Decommissioning

Removing a node from a network is done by writing the value 1 to the COMMISSIONING bit in the STATUS register. The node will restart automatically, at which point the commissioning process can be started again.

Configuration

The network does not have to be in commissioning mode when writing any form of configuration.

UART

When UART configuration is written to a gateway node the configuration will apply to the gateway node, however it will also act as a default setting for all modules in the network.

Mesh nodes behave differently in that when UART configuration is written to a mesh node the configuration only applies to the individual unit, allowing BACnet devices with different UART configuration to join a BACnet network.

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 the 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 fetched via the BACNET_STATUS register.