C程序计算555定时器的频率和占空比

Question

您好，我一直收到一个错误信息，说我的函数，电阻和频率任务是未定义的。我对这是什么意思感到困惑。我附上了我的代码，希望可以被引导到正确的方向，因为这是难倒我。谢谢。我声明并定义了原型并调用了函数，所以我搞不懂为什么编译器不接受这些代码并进行编译。

#include <stdio.h>

void resistor (void);
void freqduty (float ra, float rb, float c); // Prototype function for frequency and duty cycle
int main (void)
{
    int choice; // choice to run program from start menu or quit
    

    while (1)
    {
        // Menu for entering resistor and capacitor values
        printf("Welcome to the 555 Timer Frequency and Duty Cycle Calculator\n");
        printf("Please enter two resistor values in between ");
        printf("1 kOhms and 100 kOhms and a capacitor value\n\n");
        printf("Menu\n\n");
        printf("1. Continue\n");
        printf("2. Exit\n");
        scanf("%d",&choice);
  
        switch (choice)
            {
                case 1: resistor();
                    break;
                case 2: printf("Goodbye\n"); 
                    break;
                default: printf("Wrong Choice. Enter again\n");
                    break;
            } 
    
void resistor (void);

    float ra, rb, c; // Float variables for two resistor values and capacitor

    while(1) // While loop to gather resistor A value
    
    {
    
    printf("Enter a value for Resistor Ra (kOhms):  "); // First Resistor Value
    scanf("%f", &ra);
    
        if(ra < 1 || ra > 100) // Will repeat loop until value between 1 and 100 is entered
        
            printf("Invalid selection, choose again.\n");
            
        else
        
            break; // breaks loop when valid data is entered
    
    }
    
    while(1)
   
    {
    
    printf("Resistor Rb (kOhms):  "); // Second Resistor Value
    scanf("%f", &rb);
    
        if(rb < 1 || rb > 100) // Will repeat loop until value between 1 and 100 is entered
        
            printf("Invalid selection, choose again.\n");
            
        else 
        
            break; // breaks loop when valid data is entered
    
    }
    
    while(1)
   
    {
    
    printf("\nCapacitor (uF) :  "); // Capacitor Value
    scanf("%f", &c);
        
        if(c <= 0)
                
            printf("Invalid selection, choose again.\n");
        
        else 
        {
            
            freqduty (ra, rb, c); // call function to compute frequency and duty cycle
            break; // break while loop and restart program from menu selection screen
    
        }
        
         break;
    }
    void freqduty (float ra, float rb, float c) // function to compute frequency and duty cycle
            {
            
                float freq, dutycyc, add; // Float variables for frequency and duty cycle equations
                
                freq = 2.0 * rb;
                add = (1.44 / (ra + ((2.0 * rb) * c))); 
                dutycyc = (rb / (ra + (2.0 * rb)));
    
                printf("\nThe frequency for these values entered is %.2f and the duty cycle");
                printf(" is %.2f \n\n", freq , dutycyc);    
                printf("%f     %f     %f", ra, rb, c);      
    
            }   
    }
    
    return 0;
    
}

Answer 1

您在文件范围内声明了这两个函数。您在函数main()中定义了两个函数。这意味着它们对于main()函数是局部的，并且在外部是不可见的。

而且，在使用它们的时候，它们还没有定义。

重新排列代码，它就有机会工作了。

我刚刚注意到，他们实际上在main()中定义了while(1)，这是非常不寻常的。