Network Topology

To properly design your network, you should understand a little bit about network topology. Networks can be loosely divided into two main categories, based on the way the devices are connected to each other and to the master.

Daisy chain topology – in a daisy-chained network, all of your devices are connected in a chain- like fashion. The master controller connects to a slave device, which in turn connects to another slave device, which connects to another slave device, and so on, and so on. Figure 1 shows a daisy-chained network.

Star topology – in a star network, all of your devices can connect to a central point. The master connects to each device directly, as shown in Figure 2.

The most basic 1-Wire network consists of a computer connected to a master adaptor, which in turn connects to a slave device. A basic 1-Wire network is illustrated in Figure 3.

When expanding this basic network, 1-Wire masters must follow a daisy-chain topology. New devices are connected to the existing devices as shown in Figure 4, which shows a simple daisy- chained 1-wire network.

Although simple daisy-chained networks are sufficient for many applications, they can be limiting. Depending on the physical location of your master and devices, it might be desirable to run your cable directly from each device (or a subgroup of your devices) to the master. Also, there is a limit to how long a cable you can run from your master to each slave device (see the length of cable discussion below). To expand your network in a star configuration, you can make use of a 1-Wire hub. The hub manages the communication between the master and the sub-networks, enabling the master to control multiple sub-networks without conflict. A typical 1-Wire network using a hub is illustrated in Figure 5.

Regardless of the topology of your network, there are some wiring requirements you should be aware of. We recommend using Cat 5 cable for all of your 1-Wire networks. Other cable types can be used, but you should research their use carefully as other wire can introduce additional limitations. The total length of cable on each individual run from the master adaptor should not exceed 300 meters. You should not run your 1-Wire cable near or in parallel with electrical power lines, as the power lines can cause interference.