Finding the Balance in Code Comments for Embedded Programming

In the vast field of embedded software development, code comments have always been a controversial topic. Some teams adhere to the belief that “code is documentation,” arguing that excellent code should be self-explanatory; while others advocate for detailed code comments, believing that comments can help other developers understand the logic and intent of the code more quickly. So, should we comment in embedded programming? How can we avoid excessive commenting or insufficient commenting?

The Value and Significance of Comments

Comments, as part of the code, are not without purpose. Their main role is to provide additional information to the reader, helping them better understand the code. When the code involves complex algorithms, special implementations, or critical logical nodes, appropriate comments can significantly reduce the reading difficulty and improve development efficiency.

For example, in an embedded algorithm involving complex mathematical operations, comments can explain the meaning of each variable, the purpose of the calculations, and possible optimization points. This way, other developers can grasp the core ideas more quickly while reading the code and participate in the project development.

Additionally, comments can be used to explain special techniques, implementations, and design decisions within the code. This information is very valuable for subsequent maintainers, helping them better understand the reasons and logic behind the code.

The Pitfalls of Excessive Commenting

However, excessive commenting can also lead to some problems. Too many comments not only increase the maintenance cost of the code but can also make the code appear lengthy and difficult to understand. When the logic of the code changes, if the related comments are not updated in a timely manner, it may cause inconsistencies and mislead the reader.

Here are some examples of overly commented code:

【Code Example 1: Overly Explaining Simple Code】

// Define a variable to store the calculation result  int sum = 0;    // Iterate through the array to calculate the sum of all elements  for (int i = 0; i < arraySize; i++) {      // Add the current element to the variable sum      sum += array[i];  }    // Return the calculated sum  return sum;

In this example, the code itself is very intuitive, and each step is clear. However, the comments provide detailed explanations for every step, making the code appear redundant and unnecessary.

Code Example 2: Repeating Code Content

// Initialize UART serial communication  void UART_Init(void) {      // Set baud rate to 9600      UART_SetBaudRate(9600);      // Set data bits to 8      UART_SetDataBits(8);      // Set stop bits to 1      UART_SetStopBits(1);      // Enable UART serial communication      UART_Enable();  }

In this example of UART serial communication initialization, the comments merely repeat what the function calls are doing. These comments do not provide any additional valuable information, making the code appear redundant.

Best Practices for Commenting

So, when should we comment in embedded programming? Here are some suggested best practices:

1. Comment on complex algorithms and logic: When the code involves complex mathematical operations, control logic, or data processing, appropriate comments can help the reader understand how the code works and its implementation. You can explain the core ideas of the algorithm, key steps, and possible optimization points.

// Use the Kalman filter algorithm for sensor data fusion  // The KalmanFilter() function takes the current measurement and the last prediction as input  // Returns the updated prediction  float kalmanFilter(float measurement, float previousPrediction) {      // ... Algorithm implementation details ...      return updatedPrediction;  }

1. Explain special implementations and techniques: When the code uses special implementations, techniques, or design patterns, comments can explain the reasons and purposes behind them. This helps other developers understand the design thinking of the code and avoid mistakenly modifying or deleting critical code during subsequent maintenance.

// Use bit manipulation to optimize storage and computation efficiency  // Pack two 8-bit unsigned integers into a 16-bit integer  uint16_t packValues(uint8_t value1, uint8_t value2) {      return (value1 << 8) | value2;  }

1. Provide comments for interfaces and function calls: For external interfaces and function calls, comments should explain their input parameters, return values, possible error conditions, and usage notes. This helps other developers correctly call and use these functions, reducing the likelihood of errors.

// The UART_SendByte() function is used to send a byte of data via UART  // The parameter data represents the byte of data to be sent  // The return value indicates whether the sending was successful  int UART_SendByte(uint8_t data) {      // ... Implementation of sending data ...      return success;  }

1. Avoid excessive commenting on simple code: For simple and intuitive code, avoid excessive commenting. Clear and straightforward code should be self-explanatory; too many comments will only make the code appear lengthy and difficult to understand.

Principles of Commenting

When writing comments, we need to follow some basic principles to ensure the effectiveness and readability of the comments:

1. Accuracy: Comments should accurately reflect the actual functionality and behavior of the code.

// Correct comment  // This function calculates the sum of two integers  int add(int a, int b) {      return a + b;  }    // Incorrect comment  // This function is used to implement complex mathematical operations

1. Conciseness: Avoid lengthy and redundant expressions.

// Lengthy comment  // This function is used to calculate the sum of two numbers; it takes two integer parameters and returns their sum  int sum(int x, int y) {      return x + y;  }    // Concise comment  // Calculate the sum of two integers

1. Consistency: Maintain consistency in comment style.

// Consistent comment style  // Initialize UART communication parameters  void uart_init_params(void) {      // Set baud rate      uart_set_baudrate(9600);      // Set data bits      uart_set_databits(8);  }    // Inconsistent comment style  // Initialize UART parameters  void initialize_uart(void) {      // baudrate: 9600      set_baud(9600);  }

1. Update and maintain: When the logic of the code changes, update the relevant comments in a timely manner.

// Old code and comment  // Calculate the product of two numbers  int multiply(int a, int b) {      return a * b;  }    // Modified code and updated comment  // Calculate the product of two integers, considering integer overflow  int multiply_safe(int a, int b) {      if (a > INT_MAX / b || b > INT_MAX / a) {          // Handle overflow case      }      return a * b;  }

Commenting Techniques

Here are some tips and examples for writing comments:

1. Use natural language: Ensure that the language of the comments is clear and easy to understand.

// Use bubble sort algorithm to sort the array in ascending order  void bubble_sort(int arr[], int size) {      // ... Sorting algorithm implementation ...  }

1. Explain design decisions: When the code uses special techniques or design decisions, explain the reasons behind them.

// Use bitwise operations to implement fast multiplication to reduce computation time  int fast_multiply(int a, int b) {      int result = 0;      while (b > 0) {          if (b & 1) {              result += a;          }          a <<= 1;          b >>= 1;      }      return result;  }

1. Provide comments for complex logic: When the code logic is complex, provide detailed comments to explain.

// Implement state machine state transition logic  void state_machine(int input) {      static int currentState = STATE_IDLE;      switch (currentState) {          case STATE_IDLE:              if (input == TRIGGER_EVENT) {                  currentState = STATE_ACTIVE;                  // Initialize resources needed for active state                  initialize_resources();              }              break;          case STATE_ACTIVE:              // Process input events in active state              process_input(input);              if (input == EXIT_EVENT) {                  currentState = STATE_IDLE;                  // Clean up resources used in active state                  cleanup_resources();              }              break;          // ... Other state handling ...      }  }

1. Avoid redundant comments: Do not repeat information that the code itself already conveys.

// Incorrect comment, repeats code content  int max_value(int a, int b) {      int result = (a > b) ? a : b; // Return the larger of a and b      return result;  }    // Correct comment, explains additional behavior or constraints of the function  int max_value_non_negative(int a, int b) {      // Ensure both a and b are non-negative and return the larger of the two      if (a < 0 || b < 0) {          // Handle error case or return default value      }      int result = (a > b) ? a : b;      return result;  }

By following the principles and writing techniques for comments, along with specific code examples, we can write clear and effective code comments.

Conclusion

In embedded programming, code comments are a double-edged sword. Appropriate comments can enhance the readability and maintainability of the code, helping other developers better understand it; while excessive comments may increase maintenance costs and make the code appear lengthy and difficult to understand. Therefore, we need to find a balance and use comments reasonably based on the actual situation and needs of the code.

By adhering to principles such as accuracy, conciseness, consistency, and timely updates, as well as employing techniques like using natural language, targeting the audience, and explaining why, we can write clear and effective code comments. The ultimate goal is to make the code the best documentation, allowing readers to easily understand its logic and intent, thereby improving the overall development efficiency and quality of the project.