Ethernet output mailbox - Simulink, PLECS and C++ documentation

Table of Contents

The Ethernet output mailbox block allows sending up to 1024 bytes of data via Ethernet using the UDP/IP protocol (in SDK versions prior to 2025.2, the size limit was 32-bit). To receive data via Ethernet using the UDP/IP protocol, the Ethernet input mailbox should be used.

It supports two operating modes:

On-demand mode: the user manually triggers the message transmissions.
Periodical mode: the message is sent periodically, whether the data has been changed or not. The user can configure the transmission frequency.

Simulink block

Signal specification

The first input is the data to send. The accepted data type is specified by the Signal coding format parameter. This data can be provided as a vector, with its size defined by the Number of signals parameter. The maximum supported data size is 1024 bytes. (e.g. with Signal coding format set to uint32 and Number of signals set to 100, the data size will be 4 x 100 = 400 bytes)
The second input is the send data signal. It is used to initiate a data transmission when the on-demand mode has been selected. Data is sent upon a rising edge on this signal.

Parameters

Ethernet port number: sets the destination port to which the data will be sent.
Ethernet IP address : selects the IP address to whom the data will be sent.
Signal coding format: defines the data type accepted in the data input (int8, int16, int32, uint8, uint16, uint32, float32, or float64).
Number of signals: specifies the vector size of the data to be sent.
Byte order : defines the byte order in which the data will be sent. (little-endian or big-endian)
Tx frequency : sets the data transmission frequency if the periodical mode has been selected.

Ethernet output mailbox Simulink dialog parameters IP address

PLECS block

Signal specification

The first input is the data to send. The accepted data type is specified by the Signal coding format parameter. This data can be provided as a vector, with its size defined by the Number of signals parameter. The maximum supported data size is 1024 bytes. (e.g. with Signal coding format set to uint32 and Number of signals set to 100, the data size will be 4 x 100 = 400 bytes)
The second input is the send data signal. It is used to initiate a data transmission when the on-demand mode has been selected. Data is sent upon a rising edge on this signal.

Parameters

Ethernet port number: sets the destination port to which the data will be sent.
Ethernet IP address: selects the IP address to whom the data will be sent.
Signal coding format: defines the data type accepted in the data input (int8, int16, int32, uint8, uint16, uint32, float32, or float64).
Number of signals: specifies the vector size of the data to be sent.
Byte order: defines the byte order in which the data will be sent. (little-endian or big-endian)
Tx frequency: sets the data transmission frequency if the periodical mode has been selected.

The Ethernet IP addresses can be configured in the Imperix Controllers’ target window (Coder → Coder option → Target).

C++ functions

bool Eth_ConfigureOutputMailbox(unsigned int mailboxId, unsigned int port, const char* ipAddress, float maxTxFrequency = 100, tEndianness endianness = LITTLE_ENDIAN, size_t msgLength = 4);Code language: C++ (cpp)

Configures an Ethernet UDP output mailbox.

It has to be called in UserInit().

Parameters

mailboxId: a unique id used to distinguish mailboxes from each other. This id must be unique throughout the code for all ETH and CAN input/output mailboxes.
port: the destination UDP port number to which the data will be sent.
ipAddress: the destination IP address to whom the data will be sent.
maxTxFrequency: maximal frequency at which data can be sent. The frequency must be a multiple of the main interrupt frequency. If the requested frequency is not achievable, it will automatically be set to the closest valid frequency.
endianness: defines the bytes order. BIG_ENDIAN (most significant byte first) or LITTLE_ENDIAN (least significant byte first)
msgLength: size in bytes of the message, for best perfomance it is advised to keep it under 1024 bytes

Return value

bool: returns false if too many output mailboxes were created or if the port was already assigned to another ETH output mailbox.

int Eth_Write(unsigned int mailboxId, void* data, size_t size);Code language: C++ (cpp)

int Eth_Write(unsigned int mailboxId, unsigned int dataLow);Code language: C++ (cpp)

int Eth_Write(unsigned int mailboxId, int dataLow);Code language: C++ (cpp)

int Eth_Write(unsigned int mailboxId, float dataLow);Code language: C++ (cpp)

These functions are used to send data on Ethernet using UDP.

They have to be called during the control interrupt.

Parameters

maildboxId: a unique ID used to distinguish mailboxes from each other. This ID must be unique throughout the code for all ETH and CAN input/output mailboxes.
data: data which will be sent.
size: size in bytes of the data to copy, must match the size declared during mailbox creation

Return value