查看“树莓派系列教程：按键”的源代码


上两章我们讲解了在树莓派上如何点亮一个LED灯，这一章我们讲解一下按键以及事件中断。
 一、bcm2835

<syntaxhighlight lang="python">
#include <bcm2835.h>
#include <stdio.h>

#define  KEY  20
int main(int argc, char **argv)
{
    if (!bcm2835_init())return 1;
    bcm2835_gpio_fsel(KEY, BCM2835_GPIO_FSEL_INPT);
    bcm2835_gpio_set_pud(KEY, BCM2835_GPIO_PUD_UP);
    printf("Key Test Program!!!!\n");   
    while (1) 
    {   
        if(bcm2835_gpio_lev(KEY) == 0)
        {   
            printf ("KEY PRESS\n") ;
            while(bcm2835_gpio_lev(KEY) == 0)
                bcm2835_delay(100);
        }   
        bcm2835_delay(100);
    }   
    bcm2835_close();
    return 0;
}</syntaxhighlight> 

 
编译并执行，按下按键会看到窗口显示”KEY PRESS”，按Ctrl+C结束程序。



<syntaxhighlight lang="python">
gcc –Wall key.c –o key –lbcm2835

sudo ./key</syntaxhighlight>
注：（1）bcm2835_gpio_fsel(KEY, BCM2835_GPIO_FSEL_INPT);设置管脚为输入模式
      （2）bcm2835_gpio_set_pud(KEY, BCM2835_GPIO_PUD_UP);设置为上拉模式
      （3） bcm2835_gpio_lev(KEY)；读取管脚状态
    二、wiringPi
<syntaxhighlight lang="python">
#include <stdio.h>
#include <wiringpi.h>

char KEY = 28; 

int main()
{
    if (wiringPiSetup() < 0)return 1 ; 
    pinMode (KEY,INPUT);
    pullUpDnControl(KEY, PUD_UP);
    printf("Key Test Program!!!\n");
    while(1)
    {   
        if (digitalRead(KEY) == 0)  
        {   
            printf ("KEY PRESS\n") ;
            while(digitalRead(KEY) == 0)
                delay(100);
        }   
        delay(100);
    }   
}</syntaxhighlight>
     编译并执行，按下按键会看到窗口显示”KEY PRESS”，按Ctrl+C结束程序。
<syntaxhighlight lang="python">
gcc –Wall key.c –o key –wiringPi

sudo ./key</syntaxhighlight>
注：（1）pinMode (KEY,INPUT);设置管脚为输入模式
      （2）pullUpDnControl(KEY, PUD_UP);设置为上拉模式
      （3） <span lang="EN-US" mso-bidi-language:ar-sa="" mso-font-kerning:1.0pt="" style="font-size:9.0pt;font-family:
" tahoma="">digitalRead(KEY)；读取管脚状态
通过中断的方式编程
<syntaxhighlight lang="python">
/* Interrupt.c
 * you can build this like: 
 * gcc -Wall Interrupt.c -o Interrupt -lwiringPi
 * sudo ./Interrupt
*/
#include <stdio.h>
#include <wiringPi.h>

#define button 28
char flag = 0;
void myInterrupt()
{
	flag ++;
}

int main()
{
	if(wiringPiSetup() < 0)return 1;
	pinMode(button,INPUT);
	pullUpDnControl(button,PUD_UP);
	if(wiringPiISR(button,INT_EDGE_RISING,&amp;myInterrupt) < 0)
	{
		printf("Unable to setup ISR \n");
	}
	printf("Interrupt test program\n");
	while(1)
	{
		if(flag)
		{
			while(digitalRead(button) ==0);
			printf("button press\n");
			flag = 0;
		}
	}
}</syntaxhighlight>
<span style="font-size:9.0pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma;color:#555555;
background:white">编译并执行
<syntaxhighlight lang="python">
gcc –Wall Interrupt.c –o Interrupt -lwirngPi

sudo ./Interrupt</syntaxhighlight>
 注：（1）wiringPiISR(button,INT_EDGE_FALLING,&amp;myInterrupt)；设置中断下降沿触发，myInterrupt为中断处理函数。
      三、python
<syntaxhighlight lang="python">
#!/usr/bin/python
# -*- coding:utf-8 -*-
import RPi.GPIO as GPIO
import time

KEY = 20

GPIO.setmode(GPIO.BCM)
GPIO.setup(KEY,GPIO.IN,GPIO.PUD_UP)
while True:
    time.sleep(0.05)
    if GPIO.input(KEY) == 0:
        print("KEY PRESS")
        while GPIO.input(KEY) == 0:
            time.sleep(0.01)</syntaxhighlight>
执行程序，按下按键会看到窗口显示”KEY PRESS”，按Ctrl+C结束程序。
<syntaxhighlight lang="python">
sudo python key.py</syntaxhighlight>
注：（1）GPIO.setup(KEY,GPIO.IN,GPIO.PUD_UP) 设置管脚为上拉输入模式
    （2）GPIO.input(KEY） 读取管脚值
通过中断模式编程
<syntaxhighlight lang="python">
#!/usr/bin/python
# -*- coding:utf-8 -*-
import RPi.GPIO as GPIO
import time

KEY = 20

def MyInterrupt(KEY):
    print("KEY PRESS")

GPIO.setmode(GPIO.BCM)
GPIO.setup(KEY,GPIO.IN,GPIO.PUD_UP)
GPIO.add_event_detect(KEY,GPIO.FALLING,MyInterrupt,200)

while True:
    time.sleep(1)</syntaxhighlight>
 注：（1）def MyInterrupt(KEY): 定义中断处理函数

 （2） GPIO.add_event_detect(KEY,GPIO.FALLING,MyInterrupt,200) 增加事件检测，下降沿触发，忽略由于开关抖动引起的小于200ms的边缘操作。
关于树莓派事件中断编程请参考：
http://www.guokr.com/post/480073/focus/1797650173/