Modbus Integration
A Navtech Radar with the SafeGuard functionality enabled can act as a Modbus master or a Modbus slave device.
In addition to a single register that presents the alarm state of the six SafeGuard detection & reporting zones, there are further registers which allow a connected device to report various aspects of its' health.
The key aspects of the radar’s Modbus configuration are shown in the screenshot of the radar’s web user interface below. These settings apply, irrespective of whether the SafeGuard functionality is enabled in the radar.
From this page, the following settings are available:
Modbus Mode: This is the data output mode.
None: Disabled
Master: The radar will pole other devices that are operating as a slave.
Slave: The radar acts as a server and makes alarm data available to the Modbus master.
Relay: The radar will output nav mode area alarms via a Relay unit instead of using Modbus.
Modbus Address: This is the IP Address of the slave and is only available to be used if the radar is acting as a Master. In slave mode, the address is the same as the radar.
Port: This is the port used by Modbus in order to connect to the slave.
Health Offset: This is the register offset used by Modbus. If this value is set to 0, the radar’s health data will be presented in the lowest numbered Modbus holding registers.
The six SafeGuard alarm states are presented by the value in a specific Modbus holding register. This register can be configured through the radar’s web user interface as shown below:
Note that this functionality is only supported in radars with firmware v3.0.0.92 or later.
The screenshot of a very simple Modbus listener, below, shows how the radar health is presented in the lowest registers, and how the six alarm states are presented.
The Watchdog Counter is an incrementing number - attached devices can monitor the change in this to identify that the Modbus communication link is correct and operational.
Radar Health is presented as nine bits. The first three bits represent a “not-OK” status relating to the radar’s temperature, rotation speed and its' data output rate. The next batch of three bits represent a “warning” condition against each of the same three categories, and the final three bits represent an “OK” condition for each of the three health categories - as is shown in the image above.
The next three registers, as shown in the screenshot above, present the radar’s Operating Temperature (in DegC), its' Rotation Rate in mHz, and a value of Packet Rate, which is the number of azimuths of data presented per second.