Experiment 6 examination

《 Embedded system design 》 The test

 Examination requirements ：
 stay Linux Compiled under the system LED、 Key and buzzer program ,
 The object file generated through cross compilation is uploaded to the development board through the serial port ,
 And execute the program on the development board and observe the results .
 specific requirement ：
	 The initial frequency is 10,LED In the state of total extinction ,
	 Definition 3 A button ,
		 Key 1：
			 Press the key every time to increase the frequency 1,
			 When the frequency is greater than or equal to 19 Return to the initial value ,
			 The frequency is increased every time 2 Light up a LED The lamp 
			（ namely ： The frequency is 18 when LED In the state of full illumination ）;
		 Key 2：
			 Press the key every time to reduce the frequency 1,
			 When the frequency is less than or equal to 1 Return to the initial value ,
			 Each time the frequency decreases 2 One goes out at a time LED The lamp （ Only for LED When on ）;
		 Key 3：
			 Turn off the buzzer 、LED Total destruction 、 And quit the program .

The experimental steps ：

 A little 

Experimental code ：

#include<stdio.h>
#include<fcntl.h>
#include<stdlib.h>

int main() {
    

    int fdk, fdp, fdl;
    int i;
    int frq = 10;

    int twice_inc = 0;
    int twice_dec = 0;
    // Which lamp ,  Less than which_led Liang Liang 
    int which_led = 0;

    char key[4] = {
    '0', '0', '0', '0'};

    fdk = open("/dev/buttons", O_RDONLY);
    fdp = open("/dev/pwm", O_RDONLY);
    fdl = open("/dev/leds",O_WRONLY);
    if(fdk<0) {
    
        printf("Open buttons ERROR!\n");
        exit(1);
    }
    if(fdp<0) {
    
        printf("Open PWM ERROR!\n");
        exit(1);
    }
    if(fdl<0) {
    
        printf("Open leds ERROR!\n");
        exit(1);
    }

    for(i = 0; i < 4; i++) ioctl(fdl, 0, i);

    // The main program 
    for(;;) {
    
        char cukey[4] = {
    '0', '0', '0', '0'};
        read(fdk, cukey, sizeof cukey);
        for(i = 0; i < 4; i++) {
    
            if(key[i] != cukey[i]) {
    
                key[i] = cukey[i];
                if(key[i] == '1') {
    
                    switch(i) {
    
                    case 0:
                        frq++;
                        twice_dec = 0;
                        twice_inc++;
                        if(frq == 19) frq = 10;
                        if(twice_inc == 2) {
    
                            if(which_led != 4) {
    
                                ioctl(fdl, 1, which_led);
                                which_led++;
                            }
                            twice_inc = 0;
                        }
                        break;
                    case 1:
                        frq--;
                        twice_inc = 0;
                        twice_dec++;
                        if(twice_dec == 2) {
    
                            if(which_led != 0) {
    
                                which_led--;
                                ioctl(fdl, 0, which_led);
                            }
                            twice_dec = 0;
                        }
                        if(frq == 1) frq = 10;
                        break;
                    case 2:
                        ioctl(fdp, 0);
                        for(i = 0; i < 4; i++) ioctl(fdl, 0, i);
                        close(fdk);
                        close(fdp);
                        close(fdl);
                        exit(1);
                        break;
                    default:
                        printf("Invalid button!\n");
                    }
                    ioctl(fdp, 1, frq);

                    printf("------------------------------\n");
                    printf("which_led = %d\n", which_led);
                    printf("twice_inc = %d\ntwice_dec = %d\n", twice_inc, twice_dec);
                    printf("frq = %d\n", frq);
                    printf("------------------------------\n\n");

                }
            }
        }
    }
    return 0;
}