UDP Data Exchange by Using Shared Ethernet Board

This example shows how to set up two-way data exchange by using an Ethernet board that is shared with the connection between the development and target computers. Using this configuration, you can communicate between two Simulink^® Real-Time™ systems, between the Simulink Real-Time and Simulink products, or between two Simulink models. When one or both of the systems are running as a non-real-time Simulink model, be sure to set the sample time.

This example does not require configuring a dedicated Ethernet card because the example uses the connection between the development and target computers.

The example models are named slrt_ex_udpsendreceiveA and slrt_ex_udpsendreceiveB. Replace the port and IP address examples with ports and addresses as required by your network. This example uses a target computer located at IP address 192.168.7.5 and uses a development computer located at IP address 192.168.7.2.

UDP Data Transfer

The models transfer two different data sets between them, one data set from slrt_ex_udpsendreceiveA to slrt_ex_udpsendreceiveB and another data set in the opposite direction.

For this example, the inputs are generated by using Simulink Constant blocks that use the MATLAB^® random number function (rand). The Simulink Coder™ software uses this function during code generation to generate random numbers. To generate the vector of uint8 (3x3), use the MATLAB function:

uint8(255 * rand(3,3))

because 255 is the maximum value for an unsigned 8-bit integer. The other values are generated similarly.

slrt_ex_udpsendreceiveA to slrt_ex_udpsendreceiveB

The UDP data to send is 75 bytes wide. The data to transfer is in these formats:

• [3 3] of uint8 (9 bytes)

• [1 1] of uint16 (2 bytes)

• [2 4] of double (64 bytes)

When packed, the data is aligned on 1-byte boundaries.

slrt_ex_udpsendreceiveB to slrt_ex_udpsendreceiveA

The UDP data to be sent is 79 bytes wide. The data to transfer is in these formats:

• [4 1] of single (16 bytes)

• [2 2] of double (32 bytes)

• [2 2] of uint32 (16 bytes)

• [5 3] of int8 (15 bytes)

When packed, the data is aligned on 2-byte boundaries. A zero-valued pad byte is added during packing.

Set Up slrt_ex_udpsendreceiveA

The final slrt_ex_udpsendreceiveA is shown in the figure.

The tables list the parameters for the send and receive sides of the model.

slrt_ex_udpsendreceiveA Send Side

Block	Parameter	Value
Byte Packing	Output port (packed) data type	'uint8'
	Input port (unpacked) data types (cell array)	{'uint8', 'uint16', 'double'}
	Byte alignment	1
UDP Send	Local IP address	Use host-target connection
	Local port	-1 (autoselect)
	To IP address	192.168.7.5
	To port	25000
	Sample time (-1 for inherited)	0.01

• The Length input port receives the output of a Width block that calculates the width of the signal connected to the Data port.

• The Byte Packing block settings match the Byte Unpacking block of slrt_ex_udpsendreceiveB.

slrt_ex_udpsendreceiveA Receive Side

Block	Parameter	Value
UDP Receive	Local IP address	Use host-target connection
	Local port	25000
	Receive width	80
	Receive from any source	off
	From IP address	192.168.7.2
	Sample time (-1 for inherited)	0.01
Byte Unpacking	Output port (unpacked) data types (cell array)	{'single', 'double', 'uint32', 'int8'}
	Output port (unpacked) dimensions (cell array)	{4, [2 2], [2 2], [5 3]}
	Byte alignment	2

• The second output port of the UDP Receive block is sent into a terminator. You can use this output to determine when a packet has arrived. The same is true for the outputs of the Byte Unpack block.

• The Receive width of the UDP Receive block matches the output port width of the Byte Packing block in slrt_ex_udpsendreceiveB.

• The Byte Unpacking block settings match the settings of the Byte Packing block of slrt_ex_udpsendreceiveB.

• The number of unpacked bytes is 79. The byte alignment is 2. The Byte Unpacking block assumes that the input vector includes a pad 0 to align the vector on an even-numbered boundary.

Set Up slrt_ex_udpsendreceiveB

The final slrt_ex_udpsendreceiveB model is shown in the figure.

The tables list the parameters for the receive side and the send side of the model.

slrt_ex_udpsendreceiveB Receive Side

Block	Parameter	Value
UDP Receive	Local IP address	Use host-target connection
	Local port	25000
	Receive width	75
	Receive from any source	off
	From IP address	192.168.7.5
	Sample time (-1 for inherited)	0.01
Byte Unpacking	Output port (unpacked) data types (cell array)	{'uint8', 'uint16', 'double'}
	Output port (unpacked) dimensions (cell array)	{[3 3], 1, [2 4]}
	Byte alignment	1

• The second output port of the UDP Receive block is sent into a terminator. You can use this output to determine when a packet has arrived. The same is true for the outputs of the Byte Unpack block.

• The Receive width of the UDP Receive block matches the output port width of the Byte Packing block in slrt_ex_udpsendreceiveA.

• The Byte Unpacking block settings match the Byte Packing block in slrt_ex_udpsendreceiveA.

slrt_ex_udpsendreceiveB Send Side

Block	Parameter	Value
Byte Packing	Output port (packed) data type	'uint8'
	Input port (unpacked) data types (cell array)	{'single', 'double', 'uint32', 'int8'}
	Byte alignment	2
UDP Send	Local IP address	Use host-target connection
	Local port	-1 (autoselect)
	To IP address	192.168.7.2
	To port	25000
	Sample time (-1 for inherited)	0.01

• The Length input port receives the output of a Width block that calculates the width of the signal connected to the Data port.

• The Byte Packing block settings match the settings of the Byte Unpacking block of slrt_ex_udpsendreceiveA.

• The number of unpacked bytes is 79. The byte alignment is 2. The Byte Packing block pads the output vector with 0 to align on an even-numbered boundary.