RPi 2B GPIO 测试

一、参考文档：
    1. RPi.GPIO 0.3.1a
        https://pypi.python.org/pypi/RPi.GPIO/0.3.1a#downloads
    2. Raspberry PI上操作GPIO（GPIO编程）

    3. #16 GPIO: channel is already in use
        https://sourceforge.net/p/raspberry-gpio-python/tickets/16/    

二、error：
    1. 现象：
        #pi@raspberrypi:~/programe/python $ ./ledGPIO.py 
        #./ledGPIO.py:8: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
        #  GPIO.setup(11, GPIO.OUT)
    2. 解决方法：
        add GPIO.cleanup() at the end of your program.

三、demo:
    #!/usr/bin/python

    import RPi.GPIO as GPIO
    import time

    def blink(times, delay):
        # 选择采用树莓派的引脚编号，也就是那个1到40的引脚编号。
        GPIO.setmode(GPIO.BOARD)
        # 我的led灯，一端接树莓派的1号脚，也就是最左上角的3.3V的引脚，
        # 另一端接在树莓派的11号引脚。
        GPIO.setup(11, GPIO.OUT)

        while times > 0 :
            if 0 == times%2:
                GPIO.output(11, GPIO.HIGH) # or output(11, GPIO.True)
            else:
                GPIO.output(11, GPIO.LOW) # or output(11, GPIO.True)
            time.sleep(delay)
            times -= 1

        return

    if __name__ == '__main__':
        blink(20, 1)
        GPIO.cleanup()