Px4 adds new applications

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Studied how to add new apps for four days , I tried to add... A few days ago .cpp File application , Following the Internet has failed , I tried to add one today .c The file application actually succeeded .
The first .c How to add the method to write , Later I learned how to add .cpp Let's revise it again .
This is the official manual for adding methods , It's also my reference ：

https://dev.px4.io/master/zh/apps/hello_sky.html

One 、 New file

stay src Put the folder you want （ Such as /src/modules or /src/examples） Create a new folder in , I choose to be here /src/modules The new one in is called Data_link_read Folder .
And then in Data_link_read Create a new folder .c Documents and a CMakeLists.txt file ：

Here we suggest folder names and .c Same file name

Two 、 Write .c and CMakeLists.txt file

.c Write as follows ：

__EXPORT int Data_link_read_main(int argc, char *argv[]);

int Data_link_read_main(int argc, char *argv[]) { return OK; }

To avoid the trouble of adding header files , I'll take the official manual first PX4_INFO("Hello Sky!"); The sentence is deleted , After all, our goal is to create a new application and , First, the pursuit of compiler through , Let's consider making this application implement some functions ！

CMakeLists.txt Write as follows ：

 px4_add_module(
         MODULE modules__Data_link_read
         MAIN Data_link_read
         STACK_MAIN 2000
         SRCS
         	Data_link_read.c
         DEPENDS
 )

* Be careful ：CMakeLists.txt The second line MODULE trailing “modules” Because I chose src Under the modules Folder , If you choose examples, Then it should be written ：

MODULE examples__Data_link_read

* Digression ： stay /PX4-Autopilot/cmake Several under the folder px4_XXX.cmake There are some explanations about the format in the documents , You can refer to it

3、 ... and 、 Fill in .cmake file

To ensure that the application we added can be run , You first need to make sure that the compiler takes it as PX4 Part of the firmware is compiled .
So add our application to /PX4-Autopilot/boards/px4/fmu-v5 In folder default.cmake In file ：

Here we are MODULES Add our application under .（ If your app is written in examples In the folder , Then add the application to EXAMPLES Next ）.

* Be careful ： So here's what I chose /px4/fmu-v5 Under folder default.cmake file , It's because I'm at the terminal （terminal） The statements used in compiling are make px4_fmu-v5_default. therefore , If you don't compile with px4_fmu-v5, Please select... Under the corresponding folder default.cmake Add application ！