Everyone is quite familiar with the C language, but do you have this question: why, after learning C for so long, are you still stuck at the beginner level? I have seen many summaries of others’ programming experiences and found that most of them talk about their programming skills. Everyone knows that good programming skills can significantly improve program efficiency, but such skills are summarized from extensive engineering practice. Only after having a certain foundation can one pursue these programming techniques. However, the principles of programming must be rigorously implemented from the very beginning of learning to cultivate good programming habits; one must practice the fundamentals before advancing to higher-level skills to avoid going astray.
Now, let’s briefly discuss: what principles should be followed in C language programming for embedded systems?
1. Module Division
The C language, as a structured programming language, primarily divides modules based on functionality:
(1) A functional module consists of a .c file and a .h file; the .h file contains declarations for the functions and variables of that module.
(2) Any external functions and data provided by the module for other modules to call must be declared in the .h file using the extern keyword.
(3) Functions and global variables within the module can only be defined in the .c file.
(4) Variables cannot be defined in the .h file (the difference between defining and declaring a variable is that defining allocates memory, while declaring merely informs the module containing the declaration to look for external functions and variables during linking).
2. An embedded system program consists of two types of modules written in three layers:
(1) Hardware driver modules, where each specific hardware corresponds to one module, including integrated hardware modules and external expansions.
(2) Software functional modules, which are logic functions independent of hardware built on top of hardware driver modules.
(3) The three layers are HAL (Hardware Abstraction Layer), API (Application Programming Interface), and APP (Application Logic Layer). Note: the names are borrowed to convey a general meaning. HAL is closely related to hardware driver modules and system hardware, API can be a hardware application service program built on HAL or a general function module, and APP is the functional logic that ultimately constitutes the embedded system application. HAL and API are separated to facilitate technical accumulation and improve development efficiency, while APP is customized for specific applications.
3. Requirements for Interrupt Service Routines (ISR):
(1) Cannot return a value.
(2) Cannot pass parameters to ISR.
(3) ISR should be as short and efficient as possible, and should not include operations that wait for signals.
4. Programming Style Issues
5. Basic C Language Techniques to Master
(1) Data pointers; one should not only know how to use arrays.
(2) Macro definitions, defining register addresses, defining macro functions, etc.
(3) Application of function pointers.
(4) Conditional compilation, which is often used in applications with operating systems.
6. Do not be lazy; write necessary comments well.
7. Once you achieve the above points, you can absorb advanced programming techniques.
In summary, although I have not gone into depth, I sincerely hope this can help everyone. At the same time, I hope everyone will work on more projects, reflect and summarize their work, and continuously move closer to high-paying goals!
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