Modbus Integration

Owned by John Marshall
Last updated: about 8 hours ago
4 min read

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 poll 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 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 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

Radar health is presented as a set of registers containing current status values, and a register declaring overall health status for each of the parameters. Each health status is declared as three mutually-exclusive bits, each bit representing whether the parameter is healthy, warning or unhealthy.

Radar health information varies depending on the firmware version being used, as defined below.

 

Radar health (firmware v3.1.0.415 or earlier)

Radar health status flags are defined as follows:

 

The next three registers, as shown in the screenshot below, present:

  • Operating Temperature (in Degrees C)

  • Rotation Rate in mHz

  • Packet Rate, which is the number of azimuths of data presented per second

 

The screenshot of a very simple Modbus listener, above, shows how the radar health is presented in the lowest registers, and how the health status ‘bits’ are mapped within a single register for radar firmware 3.0.0.92-3.1.0.415

Radar health (firmware v3.1.0.416 and later)

From firmware v3.1.0.416 onwards the radar health status has been extended to include CPU load. The radar health status flags have been reorganised to allow for future expansion.

The next four registers, as shown in the screenshot below, present:

  • Operating Temperature (in Degrees C)

  • Rotation Rate in mHz

  • Packet Rate, which is the number of azimuths of data presented per second.

  • CPU Load, as a percentage

 

The screenshot of a very simple Modbus listener, above, shows how the radar health is presented in the lowest registers, and how the health status ‘bits’ are mapped within a single register, for radar firmware firmware v3.1.0.416 and later