PX4SILIntFloatSend Module Documentation

Toolbox: RflySim Model

Introduction

One-sentence Description: Packages custom integer and floating-point arrays and sends them via UDP to the custom input interface of the SIL mode DLL model in CopterSim.

This module is a custom interface module in the RflySim toolchain for SIL (Software-in-the-Loop) simulation development, enabling users to pass custom data to the PX4 flight controller’s SIL simulation DLL. It packages the input 8-dimensional custom integer array and 16-dimensional custom floating-point array (note: the documentation states 16D, but the protocol specifies 20D—see Data Communication Protocol), adds a checksum and drone ID according to the PX4SILIntFloat protocol format, and transmits the packet via a specified UDP port. The port number follows the rule 30100 + (copterID - 1) * 2, supporting multi-vehicle simulation scenarios.

This module is primarily used in custom data interaction scenarios during PX4 SIL simulation development. Users can send custom configurations, reference commands, and additional sensor data generated in Simulink to the PX4 SIL simulation DLL running in CopterSim. Combined with the corresponding receiving-end custom interface, it enables customized simulation functionality development, supporting both single-vehicle and multi-vehicle SIL simulation data exchange requirements.

Port Descriptions

Input Ports

Port Name	Data Type	Dimension	Description
inSILInts	int32/double	1×8	User-defined integer data, supporting up to 8 elements
inSILFloats	double	1×20	User-defined floating-point data, supporting up to 20 elements

Output Ports

This module has no output ports.

Parameter Configuration

The following parameters can be configured in the Mask dialog box opened by double-clicking the module:

Parameter Name	Type	Default Value	Available Values/Range	Description
Target IP Address	string	127.0.0.1	Any valid IPv4 address	IP address of the host where the target CopterSim process is running
CopterID	int	1	1~255	ID number of the target drone, used to determine the UDP communication port

Parameter Setting Notes

Target IP Address

Specifies the IP address of the host where the target CopterSim process resides. If CopterSim and the Simulink simulation run on the same host, the default value 127.0.0.1 can be used.

CopterID

The sequential number of the target drone, starting from 1. The module automatically calculates the target UDP port number as 30100 + (CopterID - 1) * 2 to communicate with the SIL interface of the corresponding drone ID. When a positive CopterID is provided at the input port, the module prioritizes using the input value; otherwise, it uses the value configured in this parameter.

Module Characteristics

Characteristic	Value
Supported Data Types	double, single, int32, int
Direct Feedthrough	Yes
Sample Time	Inherited
Code Generation Support	No

Data Communication Protocol

This module sends data via UDP, following these rules:

1. Port Rule: The target UDP port number is 30100 + (CopterID - 1) * 2, where CopterID starts from 1 and represents the target drone’s sequential number.
2. Data Format: Data is packed in 10i20f format, i.e., 10 32-bit integers + 20 single-precision floats. The specific structure definition is:

struct PX4SILIntFloat{
 int checksum;         // Fixed value: 1234567897
 int CopterID;         // Target drone sequential number; uses input value if > 0, otherwise uses the module parameter value
 int inSILInts[8];     // 8-dimensional custom integer data
 float inSILFLoats[20];// 20-dimensional custom single-precision floating-point data
};

1. Target Address: The IP address of the target CopterSim is configured via module parameters.

Related Modules

Module Name	Description
PX4SILIntFloatReceive	Receives custom integer and floating-point SIL interface data from CopterSim
PX4SILActuatorSend	Sends actuator control signals to the SIL interface of CopterSim
PX4SILSensorReceive	Receives sensor simulation data from CopterSim
PX4OffboardControl	Sends control commands for PX4 offboard mode

Usage Example

For related usage examples, refer to the following path:

``` [RflySim Installation Path]/RflySimAPIs/4.RflySimModel/0.ApiExps/11.inSILAPI/1.InSILIntsFloats/2.InSILIntsFloats_sim/Readme.pdf

Please refer to Readme.pdf in the path above for complete example descriptions and operational steps.

Notes and Common Issues

• Initialization Order: CopterSim must be started first, and the PX4 SIL simulation environment must be fully initialized before running the Simulink simulation; otherwise, UDP data cannot be properly sent to the target interface.
• Dimension Matching Requirement: The input inSILInts must be a fixed 8-element integer array, and inSILFloats must be a fixed 20-element floating-point array. The module automatically truncates or pads inputs with mismatched lengths, which may cause abnormal data transmission—please strictly match the input dimensions.
• Port Number Rule: The UDP port number used by the module follows the formula 30100 + (CopterID - 1) * 2. Ensure this port is not blocked by the local firewall or occupied by other processes, and verify that the target drone’s ID in CopterSim matches the CopterID configured in the module parameters; otherwise, data reception will fail.
• CopterID Priority: If a CopterID greater than 0 is provided in the input data, the module will prioritize using this input CopterID to override the one configured in the module parameters, and will automatically adjust the target UDP port number accordingly—please take note of this behavior during usage.
• IP Address Configuration: When CopterSim and Simulink run on the same machine, Target IP Address can remain at the default 127.0.0.1; if they run on different hosts, enter the actual local IP address of the machine where CopterSim resides.
• Checksum Rule: The module automatically generates a fixed checksum 1234567897 as required; users need not manually modify the checksum field in the input data, as doing so would cause checksum verification failure on the CopterSim side, resulting in discarded received data.

Changelog

• v4.20 (2024-08-21): Initial release, implementing UDP data packaging and transmission to the inSILInts and inSILFloats interfaces of the DLL model in CopterSim.