4-Way Ethernet Bus Breakout Board Configuration

4-Way Ethernet Bus Breakout Board Configuration

This article introduces an alternative method for connecting multiple Airmatics devices to one cellular gateway utilizing the advantages of a 4-way Ethernet bus breakout board.

Why use a 4-way Ethernet bus breakout board?
When an installation has multiple -Tags they are typically connected to the cellular gateway using a daisy chain network. The biggest drawback to using a daisy chain is the failure of just one device can cause subsequent devices downstream of the gateway to lose their connection with the cloud.

This article provides a solution to this problem by outlining an alternative method of connecting multiple devices. Using a 4-way Ethernet bus breakout board each –Tag can have an independent connection to the gateway and individual devices will not lose their connection to the cloud when just one -Tag is switched off.
 
Daisy chain network
 
The configuration shown above is what many users will be familiar with. This is the simplest and most cost effective way to connect multiple devices to the cellular network.

However, the drawback is if just one AirTag is switched off there is a risk that other AirTags in the network will lose their connection to the gateway.
In the above example, if AirTag 1 were to go offline or lose power then AirTags 2 and 3 will also lose their connection to the gateway and to the cloud.
 
4-way Bus Breakout Board Network

To overcome the “power down” problem, one can utilize a so-called 4-way ethernet bus breakout board to build on the daisy chain.  This has the advantage that the network remains intact even if one or more of the AirTags is switched off.
The advantage is that any AirTag may be powered down without influencing the neighboring AirTag’s connection to the gateway.
 
Advantages and Disadvantages
The dual RJ45 connectors on the AirTag are physically separated but connected to each other via a software switch. When using a daisy chain this has the advantage that the total length of the daisy chain is defined by the maximum length between each hub which is the maximum Ethernet span of 100 m (328 ft).
In other words the length of each individual Ethernet cable can span up to 100m creating a much larger maximum length for the daisy chain network as a whole.

The 4-way ethernet bus breakout board has the disadvantage that, if used for all hubs of the daisy chain, the total length of the daisy chain is limited to 100 m (328 ft).
In some cases users may wish to use a hybrid solution where not all daisy chain hubs use the 4-way breakout board. This is a viable solution when the distance between AirTags is an issue.

​When using a third party breakout board, CMC takes no responsibility for the correct set-up, operation or support of the device. If you decide to use such a device, understand that troubleshooting the ethernet network becomes more complex.