Ethernet Variable Exchange

Ethernet Variable Exchange (ETH VE) is a simple protocol based on TCP/UDP for exchanging data over the Ethernet.

TCP/UDP utilizes the Lightweight IP (lwIP) library provided by Xilinx.

The protocol runs as a bare-metal application with a guaranteed, deterministic execution rate.

Ethernet Variable Exchange is supported by the following Typhoon HIL devices: HIL402, HIL101, HIL404, HIL602+, HIL604, HIL506, and HIL606.

ETH VE Setup

The ETH VE Setup component and dialog window are shown in Table 1.

Table 1. ETH VE Setup

Component	Component dialog	Component properties
ETH VE Setup		Override HIL device ID IP Address Ethernet port Subnet mask Execution rate

Component properties are described in Table 2.

There must be exactly one ETH VE Setup component for each HIL device that uses Ethernet Variable Exchange.

ETH VE Send

The ETH VE Send component is presented in Table 4. This block lets you alter basic settings for the send socket. In this case, the HIL device will be the client in a client-server application.

ETH VE Send represents a client. The client tries to connect to the remote server specified by Destination IP address and Destination Port after the simulation starts. If the server is accessible, an active connection is opened, system variables are packed, and transferred over Ethernet. In case of a remote server failure, the client will continue trying to reconnect.

Table 3. ETH VE Send

Component	Component dialog	Component properties
ETH VE Send		General Stream source Stream source ID Append index Sample time Execution rate Network Protocol Specify local send port Local send port Destination IP address Destination port Data Configuration

Component properties are listed in Table 4.

Configuration parameters

To change the Configuration property, use the Generate configuration button in the Data tab.

In the configuration menu, a custom payload for the data to be sent over Ethernet can be defined.

Table 5 provides an overview of the Configuration menu.

ETH VE Receive

The ETH VE Receive component is presented in Table 6. This component enables you to perform basic settings for the receive socket. For ETH VE Receive, the HIL device will represent a server in a client-server application. A model can have more than one ETH VE Receive component, provided there is a different receive port for each one.

ETH VE Receive represents a server with a passive opened connection. It waits for any client to try to connect. The server can be configured to accept an incoming connection from any client IP and port (deactivated Specify source port and Specify source IP address respectively), or to accept only from a specified IP and a specified Port. After the connection has been accepted, the server starts receiving packets, parses them, and dispatches data to the target component.

Table 6. ETH VE Receive

Component	Component dialog	Component properties
ETH VE Receive		General Execution rate Network Protocol Local receive port Specify source port Source port Specify source IP address Source IP address Data Configuration

Component properties are listed in Table 7.

Configuration parameters

To change Configuration properties, use the Generate configuration button in the Data sub menu.

In the configuration menu, a custom payload for the data received over the Ethernet can be defined.

Table 8 provides an overview of the Configuration menu options.

Connection Establishment

To establish a connection, TCP uses a three-way handshake. Before a client attempts to connect with a server, the server must first bind to a port and listen for incoming connections - this is called a passive open. Once the passive open is established, a client may initiate an active open. To establish a connection, this three-way (or 3-step) handshake occurs in the following order:

1. SYN: An active open is performed by the client sending a SYN to the server. The client sets the segment's sequence number to a random value A.
2. SYN-ACK: In response, the server replies with a SYN-ACK. The acknowledgment number is set to one more than the received sequence number i.e. A+1. The sequence number that the server chooses for the packet is another random number, B.
3. ACK: Finally, the client sends an ACK back to the server. The sequence number is set to the received acknowledgement value i.e. A+1, and the acknowledgement number is set to one more than the received sequence number i.e. B+1.

At this point, both the client and server have received an acknowledgment of the connection. Step 1 establishes the connection parameter (sequence number) for one direction, and Step 2 acknowleges this. Step 2 also establishes the connection parameter (sequence number) for the other direction, and Step 3 acknowledges this. This way, a full-duplex communication is established (Transmission Control Protocol).

Ethernet packet

The size of payload data depends on the size of the input signal of ETH VE Send component. The structure of the ETH VE payload data is shown in Figure 1.

Network setup

To establish communication between a HIL device and a PC, the following must be satisfied:

Virtual HIL support

Virtual HIL currently does not support this protocol. When using a non-real-time environment (e.g. when running the model on a local computer), inputs to this component will be discarded and outputs from this component will be zeroed.