Creating New Message Definitions

Msg File Location

The preferred message definition uses only C code to define a struct which contains the message data. This is written in a stand-alone *.h file located in the src/architecture/msgPayloadDefC folder.

If the message struct definition needs to include C++ code, then the stand-alone message definition file is stored in src/architecture/msgPayloadDefCpp folder.

The *.h file name need to be upper camel case (start with a capital letter) and end with ...MsgPayload.h. An example is SomeMsgPayload.h.

Msg Data Definition

The message data is defined through a struct definition. For example, assume the new message is to be of type SomeMsg:

#ifndef SOME_MSG_H
#define SOME_MSG_H

/*! @brief Brief description of what this message contains */
typedef struct {
    int variable1;              //!< [units] variable description
    double variable2[3];        //!< [units] variable description


The #ifndef statement ensures this header file is only included once when compiling. The struct definition needs to have the message type name followed by MsgPayload. In this case it is SomeMsgPayload. The msg payload is the data of the message. This is in contrasts to the message object which contains a copy of this message payload, as well as a message header.

Creating the Msg C/C++ Interface Files

To create message objects in C and C++ modules, you need to run python3 again from in the Terminal or command line window. This script auto-creates the corresponding C module interface files and stores them in basilisk/dist3/autoSource/cMsgCInterface. The C++ message objects are automatically created as a template class using the *.h definitions in msgPayloadDefC. Naturally no C module interface files are created for *.h files in msgPayloadDefCpp.

Running python3 re-creates the IDE project file that will now include access to the new message definition.