How do I use "serXputs(int port, ...) and related macros?

Hello, pls check the Dynamic C function reference manual at the below link, you can find the function description.

You can use the Edit menu’s “Find in Files” function to search for uses of serXputs() in other libraries and the sample programs. One example:

serXputs(SER_PORT_D, "The quick brown fox jumped")