外接按鈕控制
===


## 上拉電阻



#!/usr/bin/python
#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
#|R|a|s|p|b|e|r|r|y|P|i|.|c|o|m|.|t|w|
#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# Copyright (c) 2016, raspberrypi.com.tw
# All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# push_button_poll.py
# Response when push button is pressed with poll way
#
# Author : sosorry
# Date   : 06/22/2014

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BOARD)
BTN_PIN = 11
GPIO.setup(BTN_PIN, GPIO.IN)
previousStatus = None

try:
    while True:
        input = GPIO.input(BTN_PIN)
        if input == GPIO.LOW and previousStatus == GPIO.HIGH:
            print("Button pressed @", time.ctime())
        previousStatus = input

except KeyboardInterrupt:
    print("Exception: KeyboardInterrupt")

finally:
    GPIO.cleanup() 

# 輪詢與中斷

上面這個程式的 CPU 用量挺大的(2x%)

$ top -c

### 輪詢 (polling)

SoC 每隔一段時間檢查週邊硬體的資料

### 中斷 (interrupt)

當週邊硬體的狀態改變時 , 對 SoC 發出中斷要求

### 建立回呼函數
def mycallback()

### 綁定事件和回呼函數
add_event_detect(gpio, # 對象
　　　　　　　　edge, # 觸發條件
　　　　　　　　callback, #回呼函數
　　　　　　　　bouncetime)

#!/usr/bin/python
#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
#|R|a|s|p|b|e|r|r|y|P|i|.|c|o|m|.|t|w|
#+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# Copyright (c) 2016, raspberrypi.com.tw
# All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# push_button_interrupt.py
# Response when push button is pressed with interrupt way, and de-bounces 
# by software
#
# Author : sosorry
# Date   : 06/22/2014

import RPi.GPIO as GPIO                 
import time

GPIO.setmode(GPIO.BOARD)                
BTN_PIN = 11
WAIT_TIME = 200
GPIO.setup(BTN_PIN, GPIO.IN)

def mycallback(channel):                                                 
    print("Button pressed @", time.ctime())

try:
    GPIO.add_event_detect(BTN_PIN, GPIO.FALLING, callback=mycallback, bouncetime=WAIT_TIME)

    while True:
        time.sleep(10)

except KeyboardInterrupt:
    print("Exception: KeyboardInterrupt")

finally:
    GPIO.cleanup()          

# 小夜燈


LED_PIN = 22		
GPIO.setup(LED_PIN, GPIO.OUT)
if GPIO.input(LED_PIN)==GPIO.HIGH:
    GPIO.output(LED_PIN, GPIO.LOW)
else :
    GPIO.output(LED_PIN, GPIO.HIGH)