There are different options to build a SomatXR topology. When the distance between modules is short (<5 m), FireWire connection is recommended. For longer distances (<100 m) Ethernet PTP should be selected.
Modules can be connected to the PC with an Ethernet switch. In case of PTP, the Ethernet switch needs to be compliant to this standard (e.g., SomatXR EX23-R).
All modules should be supplied with power separately.
For more information on PTP and NTP synchronization, see Module synchronization.
Data is transferred, modules are synchronized in timing and voltage is supplied via the FireWire connections. A maximum of 12 modules can be connected in series with each other.
NOTE
Different supply voltage sources need to have the same reference potential and should be in the same voltage range. Voltage drops occur as a result of cable resistance and internal protective circuits; therefore, a considerably lower supply voltage is applied to the last module in the chain. Make sure that at least 10 V is applied to the last module.
NOTE
From source to sink, the modules must always be connected from FireWire port X102 to X101 on the next module.
To connect up to 24 modules, use a hub. Hubs are devices that connect network chains together in star configurations. This connection mode is again limited to 14 hops. A hop is the transition from one module to another (this means n-1 hops for n modules in a chain). Depending on the connection situation, 1 to 2 hops are counted in one hub. To count the total number of hops, the longest chain to the data sink must be counted (worst case).
Greater distances than 5 m in FireWire networks can be bridged with optohubs that enable distances of up to 100 m with the use of a fiber optic cable. Distances over 100 m significantly reduce the number of hubs as follows:
Another advantage in addition to wide measurement module distribution and the associated short sensor leads, is fully isolated data communication between different system components, to suppress the electromagnetic interference of high overhead line voltages in rail traffic, for example.
The supply voltage for the modules is looped through FireWire in the configuration shown below (max. 1.5 A through FireWire; for power consumption of one module see specifications in data sheet).
The advantage of this connection structure is the other modules remain active if one Ethernet cable is broken.
Reference