In-depth discussion of the role of 32 reset and SystemInit functions in the program

In 32 applications, we generally reset in two ways:

1. Press the reset button to reset the program 

2. Pull the jumper on the microcontroller to complete the 32

In the above two reset methods, for the chip, they are actually just programs triggered after the pin receives a jump delay signal. In the firmware library that comes with Keil, we can see the following program:

Here is the reset program code snippet from the library. EXPORT defines a global variable Reset_Handler. IMPORT means a function is referenced. The _main function introduced here is used to make the main function in the main function we usually write work, connecting the C program with the underlying assembler program to make the program work. When we first start learning, we often find that there is always a function in the environment written by others that we don’t know what it means: SystemInit(). We can see that the SystemInit function is introduced in line 150 of the picture, and the function is called in the next line, but it is not declared. Therefore, if we do not declare a new SystemInit function outside main when writing the main program, the program will report an error when compiling.

Just write an empty function as shown in the figure, the purpose is to trick the compiler into not reporting an error. Note that the function name here should be the same as the function name in the firmware library. 

If you get this error in Keil: 

..\OBJ\Template.axf: Error: L6218E: Undefined symbol assert_param (referred from misc.o). 

This means that you have not defined the SystemInit() function. Therefore, you can solve the problem by defining SystemInit() in any .c function. The function can be empty.