Introduction to C language programming style for AVR microcontrollers

　　Abstract: How can a beginner have a good programming style? The following article will introduce the C language programming style of AVR microcontroller.

　　Introduction to C programming style

　　1. Variable definition

　　When defining a variable, the prefix is ​​the type of variable, followed by an English word or abbreviation that represents the purpose of the variable, and the first letter of each word or abbreviation is capitalized. The various prefix abbreviations are as follows:

　　Unsigned variables use u8, u16, u32; for example: unsigned char u8Temp;

　　Signed variables use s8, s16, s32; example: char s8Temp;

　　Floating point variables use f32, d64; example: float f32Temp;

　　Structure variables use st; for example: struct Temp stTemp;

　　Use s for string variables; for example: char sTemp;

　　Array variables use a; for example: unsigned char aTemp［10］;

　　Pointer variable uses p; example: unsigned char *pTemp;

　　Enumeration variables use e; for example: enum Temp eTemp;

　　2. Macro definition

　　Use uppercase + underscore for macro definitions.

　　3. Program layout

　　Use the tab key to align the beginning of a line of program, and use the space key to align the middle of a line.

　　This prevents code confusion when different editing tools are opened.

　　4. Writing comments

　　The comments here are divided into function header comments and program code comments.

　　Function header comments use the following format

　　/*

　　*Name：

　　*Description:

　　*Created：

　　*Author：

　　*/

　　These four items are required, and others, such as the input and output parameters of the function, can be added appropriately depending on the needs of the function.

　　5. Test your code

　　While programming, you need to pay attention to adding appropriate test code, which can reduce the workload when testing the code later.

　　AVR C language excellent programming style

　　File Structure

　　Modular programs should have a good program structure. AVR C language programs have two types of user files, .c program files and .h header files. During the program writing process, the .c file needs to include the .h header file. Beginners often have problems with repeated inclusion or header file inclusion errors. I was often worried about this error at the time. Below I will use the motor drive routine I wrote to illustrate to you the excellent programming file structure.

　　There are 8 files and one description file in this project, as shown below: Download program example motor control case.

　　The number of files in the programs I wrote is basically an even number, because each structured function definition .c file will correspond to a .h file. main.c corresponds to config.h. Let's take a look at the inclusion relationship of each file. Let's take a look at the inclusion relationship and content of these files: [Recommended file inclusion order and relationship]

　　All .c files include the config.h file. For example: #include "config.h"

　　In config.h there is the following code:

　　#include "delay.h"

　　#include "device_init.h"

　　#include "motor.h"

　　This makes it less likely that incorrect inclusion relationships will occur. To prevent this, we also introduce macro definitions and precompilation. As follows:

　　#ifndef _UNIT_H__

　　#define _UNIT_H__ 1

　　//100us

　　extern void Delay100us(uint8 n);

　　//1s

　　extern void Delay1s(uint16 n); // n <= 6, when n==7, it is 1.

　　//1ms

　　extern void Delay1ms(uint16 n);

　　#endif

　　The first time this file is included, it compiles correctly and #define _UNIT_H__ 1 is set. The second time this file is included, #ifndef _UNIT_H__ is no longer true and the file is skipped.

　　Precompilation has more uses, such as compiling different statements based on different values, as follows:

　　//#pragma REGPARMS

　　#if CPU_TYPE == M128

　　#include 《iom128v.h》

　　#endif

　　#if CPU_TYPE == M64

　　#include 《iom64v.h》

　　#endif

　　#if CPU_TYPE == M32

　　#include 《iom32v.h》

　　#endif

　　#if CPU_TYPE == M16

　　#include 《iom16v.h》

　　#endif

　　#if CPU_TYPE == M8

　　#include 《iom8v.h》

　　#endif

　　The difference between #include《filename》 and #include "filename": the former includes files under the system directory include, while the latter includes files under the program directory.

　　Variable names and function names

　　Variable and function names should be as short as possible, as long as needed, and meaningful. You can use underscores or a combination of uppercase and lowercase to form variable and function names. The following compares good and bad naming methods:

　　1. OK: Delay100us();

　　Bad: Yanshi();

　　2. OK: init_devices();

　　Bad: Chengxuchushihua();

　　3. OK: int temp;

　　Bad: int dd;