Raw Ethernet / User Datagram Protocol (UDP)
The User Datagram Protocol (UDP) is a transport protocol layered on top of the Internet Protocol (IP) and is commonly known as UDP/IP.
It is analogous to TCP/IP but differentiates as follows: TCP communication can be compared to a telephone conversation where a connection is required at all times and two-way streaming data (the words spoken by each party to the conversation) are exchanged. UDP, on the other hand, can be compared to sending letters by mail (without a return address). If the other party is not found, or the letter is lost in transit, it is simply discarded.
UDP as supported by xPC Target allows you to connect your target machine to other nodes by either sharing the Ethernet port used for host/target Ethernet communication via a multi port Ethernet switch or starting with R2011a (xPC Target V. 5.0) by using a dedicated Fast Ethernet card (see below).
In case you're using R2008b or later but don't have access to R2011a and in case your other nodes are target computers you can also use a dedicated Fast Ethernet port such as provided by the IO701 together with the Raw Ethernet blocks which are part of the xPC Target library to easily recognize, send, and receive Ethernet packets.
| IO701 | Fast Ethernet Card with one port, PCI form factor |
| IO702 | Fast Ethernet Card with two ports, PCI form factor |
| IO703 | Fast Ethernet Card with one port, PMC form factor |
The advantage of using UDP via the same port used for the host/target communication is that you don't require an additional Ethernet port. The disadvantage is decreased reliability as error checking and recovery is limited if network traffic by other host-target communication data is heavy.
Therefore provided that you have sufficient I/O expansion space in your target machine and access to R2011a Speedgoat recommends to use a dedicated (low expensive) I/O module such as the IO701 for real-time UPD.
Further information about the UDP and Raw Ethernet protocol support is available in the MathWorks reference guide for xPC Target:
Real-Time UPD Communication Support
Model-Based Etheret Communications Support (Raw Ethernet)
UDP I/O support (UDP via Host-Target communication)
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