烧录完系统的 raspberryPi 3 python 2.7
官方文档 1（简略版） 官方文档2 (完整版）
sudo apt-get install python3-picamera
使用示例，in python3.4：
camera = picamera.PiCamera() camera.capture('image.jpg',resize=(320,240)) # 在 在当前文件夹下将截取图像存为image.jpg， 320*240大小 camera.close() # 使用完后一定要关闭， 否则因为端口被占用，下次调用会出错没有关闭camera对象在下次调用会出现以下错误
mmal: mmal_vc_port_enable: failed to enable port vc.null_sink:in:0(OPQV): ENOSPC mmal: mmal_port_enable: failed to enable connected port (vc.null_sink:in:0(OPQV))0x1324250 (ENOSPC) mmal: mmal_connection_enable: output port couldn't be enabled Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python3/dist-packages/picamera/camera.py", line 433, in __init__ self._init_preview() File "/usr/lib/python3/dist-packages/picamera/camera.py", line 513, in _init_preview self, self._camera.outputs[self.CAMERA_PREVIEW_PORT]) File "/usr/lib/python3/dist-packages/picamera/renderers.py", line 558, in __init__ self.renderer.inputs[0].connect(source).enable() File "/usr/lib/python3/dist-packages/picamera/mmalobj.py", line 2212, in enable prefix="Failed to enable connection") File "/usr/lib/python3/dist-packages/picamera/exc.py", line 184, in mmal_check raise PiCameraMMALError(status, prefix picamera.exc.PiCameraMMALError: Camera component couldn't be enabled: Out of resources (other than memory)常见的输出显示，四个数字+四个数点，总共 4*7+4=32个led灯管。如果采用一一对应的输入方式，至少需要32个针脚，但是实际上只有12个针脚。
所以我们采用动态方法：每一时刻只亮四个数字中的一个，并以足够快的速度在四个数字中循环，看起来就像一起亮着。
树莓派的针脚分布编号如下图：
我们这里采用BCM编码。
四位数码管的针脚与树莓派针脚的连接：
其中PORT表示数码管的编码（下图上半部分）：
下方的table中写出了各个要显示的数字所需要的A-G各个针脚的电平。由于这款3461BS四位数码管是共阳极的，所以当A-G针脚对应的输入电平为负的时候，对应的led灯管亮起。
结合GPIO模块，用python实现按照输入的参数数字字符串输出数字到数码管上： 3461BS.py（python2.7）
import RPi.GPIO as GPIO import time import sys mode0=[0,0,0,0,0,0,1] mode1=[1,0,0,1,1,1,1] mode2=[0,0,1,0,0,1,0] mode3=[0,0,0,0,1,1,0] mode4=[1,0,0,1,1,0,0] mode5=[0,1,0,0,1,0,0] mode6=[0,1,0,0,0,0,0] mode7=[0,0,0,1,1,1,1] mode8=[0,0,0,0,0,0,0] mode9=[0,0,0,0,1,0,0] PORT_TABLE=[mode0,mode1,mode2,mode3,mode4,mode5,mode6,mode7,mode8,mode9] BCM_PORT=[17,27,22,5] BCM_VALUE=[18,23,24,25,12,16,20,21] def init(): GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) for port in BCM_PORT: GPIO.setup(port,GPIO.OUT) GPIO.output(port,GPIO.HIGH) for value in BCM_VALUE: GPIO.setup(value,GPIO.OUT) GPIO.output(value,GPIO.LOW) for port in BCM_PORT: GPIO.output(port,GPIO.LOW) def light_off(): GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) for port in BCM_PORT: GPIO.setup(port,GPIO.OUT) GPIO.output(port,GPIO.LOW) for value in BCM_VALUE: GPIO.setup(value,GPIO.OUT) GPIO.output(value,GPIO.HIGH) def dp_allume(dp_index): light_off() GPIO.setup(BCM_PORT[dp_index],GPIO.OUT) GPIO.output(BCM_PORT[dp_index],GPIO.HIGH) GPIO.setup(BCM_VALUE[7],GPIO.OUT) GPIO.output(BCM_VALUE[7],GPIO.LOW) def val_allume(value,led_index): light_code=PORT_TABLE[value] light_off() for lc in range(7): if light_code[lc]==0: GPIO.setup(BCM_VALUE[lc],GPIO.OUT) GPIO.output(BCM_VALUE[lc],GPIO.LOW) else: GPIO.setup(BCM_VALUE[lc],GPIO.OUT) GPIO.output(BCM_VALUE[lc],GPIO.HIGH) for li in range(4): if li==led_index: GPIO.setup(BCM_PORT[li],GPIO.OUT) GPIO.output(BCM_PORT[li],GPIO.HIGH) else: GPIO.setup(BCM_PORT[li],GPIO.OUT) GPIO.output(BCM_PORT[li],GPIO.LOW) def value_to_list(val): num_list=[-1,-1,-1,-1,-1] if val<10: num_list[0]=int(val//1) val=val-num_list[0] num_list[2]=int(val//0.1) val=val-num_list[2]*0.1 num_list[3]=int(val//0.01) val=val-num_list[3]*0.01 num_list[4]=int(val//0.001) elif val<100: num_list[0]=int(val//10) val=val-num_list[0]*10 num_list[1]=int(val//1) val=val-num_list[1] num_list[3]=int(val//0.1) val=val-num_list[3]*0.1 num_list[4]=int(val*100) elif val<1000: num_list[0]=int(val//100) val=val-num_list[0]*100 num_list[1]=int(val//10) val=val-num_list[1]*10 num_list[2]=int(val//1) val=val-num_list[2] num_list[4]=int(val*10) elif val<10000: num_list[0]=int(val//1000) val=val-num_list[0]*1000 num_list[1]=int(val//100) val=val-num_list[1]*100 num_list[2]=int(val//10) val=val-num_list[2]*10 num_list[3]=int(val) else: pass return num_list def show(number=0,show_time=5): GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) light_off() num_list=value_to_list(number) for itr in range(5): if num_list[itr]==-1: dp_itr=itr break del(num_list[dp_itr]) tmp=time.clock() while time.clock()-tmp<show_time: for itr in range(4): val_allume(num_list[itr],itr) dp_allume(dp_itr-1) light_off() if __name__ == '__main__': if len(sys.argv)==1: show(number=float(sys.argv[1])) GPIO.cleanup() elif len(sys.argv)==2: show(number=float(sys.argv[1])) GPIO.cleanup() elif len(sys.argv)==3: show(number=float(sys.argv[1]),show_time=float(sys.argv[2])) GPIO.cleanup() else: print "Usage: 3461BS.py [SHOW_NUMBER][SHOW_TIME]"由于针脚较多，建议用面包板进行扩展：
用高低电平的变化序列来表示温度和湿度数字
每一份温湿度数据的传输大约会需要4毫秒，包括
8位的湿度整数部分8位的湿度小数部分8位的温度整数部分8位的温度小数部分8位的校验和每一位数据大约持续100微秒
传感器的通路连接分为两部分
1. 握手阶段
树莓派向传感器发送一个开始信号：传感器默认为高电平，树莓派输出一个至少持续18毫秒的低电平后重新拉回高电平，持续20-40微秒传感器向树莓派回复：传感器将电平降为低电平，持续80微秒后重新将电平拉回高电平，持续80微秒2. 数据传输阶段 每一位数据（0或1）都以50微秒的低电平开始，并以高电平结束。 其中表示0的高电平持续26-28微秒，表示1的高电平持续70微秒。
温湿度传感器的针脚连接：
解码python(2.7)文件： dht11.py
#! /usr/bin/python* import time import RPi.GPIO as GPIO class DHT11Result: 'DHT11 sensor result returned by DHT11.read() method' ERR_NO_ERROR = 0 ERR_MISSING_DATA = 1 ERR_CRC = 2 error_code = ERR_NO_ERROR temperature = -1 humidity = -1 def __init__(self, error_code, temperature, humidity): self.error_code = error_code self.temperature = temperature self.humidity = humidity def is_valid(self): return self.error_code == DHT11Result.ERR_NO_ERROR class DHT11: 'DHT11 sensor reader class for Raspberry' __pin = 0 def __init__(self, pin): self.__pin = pin def read(self): GPIO.setup(self.__pin, GPIO.OUT) # send initial high self.__send_and_sleep(GPIO.HIGH, 0.05) # pull down to low self.__send_and_sleep(GPIO.LOW, 0.02) # change to input using pull up GPIO.setup(self.__pin, GPIO.IN, GPIO.PUD_UP) # collect data into an array data = self.__collect_input() # parse lengths of all data pull up periods pull_up_lengths = self.__parse_data_pull_up_lengths(data) # if bit count mismatch, return error (4 byte data + 1 byte checksum) if len(pull_up_lengths) != 40: return DHT11Result(DHT11Result.ERR_MISSING_DATA,0,0) # calculate bits from lengths of the pull up periods bits = self.__calculate_bits(pull_up_lengths) # we have the bits, calculate bytes the_bytes = self.__bits_to_bytes(bits) # calculate checksum and check checksum = self.__calculate_checksum(the_bytes) if the_bytes[4] != checksum: return DHT11Result(DHT11Result.ERR_CRC, 0, 0) # ok, we have valid data, return it return DHT11Result(DHT11Result.ERR_NO_ERROR, the_bytes[2], the_bytes[0]) def __send_and_sleep(self, output, sleep): GPIO.output(self.__pin, output) time.sleep(sleep) def __collect_input(self): # collect the data while unchanged found unchanged_count = 0 # this is used to determine where is the end of the data max_unchanged_count = 100 last = -1 data = [] while True: current = GPIO.input(self.__pin) data.append(current) if last != current: unchanged_count = 0 last = current else: unchanged_count += 1 if unchanged_count > max_unchanged_count: break return data def __parse_data_pull_up_lengths(self, data): STATE_INIT_PULL_DOWN = 1 STATE_INIT_PULL_UP = 2 STATE_DATA_FIRST_PULL_DOWN = 3 STATE_DATA_PULL_UP = 4 STATE_DATA_PULL_DOWN = 5 state = STATE_INIT_PULL_DOWN lengths = [] # will contain the lengths of data pull up periods current_length = 0 # will contain the length of the previous period for i in range(len(data)): current = data[i] current_length += 1 if state == STATE_INIT_PULL_DOWN: if current == 0: # ok, we got the initial pull down state = STATE_INIT_PULL_UP continue else: continue if state == STATE_INIT_PULL_UP: if current == 1: # ok, we got the initial pull up state = STATE_DATA_FIRST_PULL_DOWN continue else: continue if state == STATE_DATA_FIRST_PULL_DOWN: if current == 0: # we have the initial pull down, the next will be the data pull up state = STATE_DATA_PULL_UP continue else: continue if state == STATE_DATA_PULL_UP: if current == 1: # data pulled up, the length of this pull up will determine whether it is 0 or 1 current_length = 0 state = STATE_DATA_PULL_DOWN continue else: continue if state == STATE_DATA_PULL_DOWN: if current == 0: # pulled down, we store the length of the previous pull up period lengths.append(current_length) state = STATE_DATA_PULL_UP continue else: continue return lengths def __calculate_bits(self, pull_up_lengths): # find shortest and longest period shortest_pull_up = 1000 longest_pull_up = 0 for i in range(0, len(pull_up_lengths)): length = pull_up_lengths[i] if length < shortest_pull_up: shortest_pull_up = length if length > longest_pull_up: longest_pull_up = length # use the halfway to determine whether the period it is long or short halfway = shortest_pull_up + (longest_pull_up - shortest_pull_up) / 2 bits = [] for i in range(0, len(pull_up_lengths)): bit = False if pull_up_lengths[i] > halfway: bit = True bits.append(bit) return bits def __bits_to_bytes(self, bits): the_bytes = [] byte = 0 for i in range(0, len(bits)): byte = byte << 1 if (bits[i]): byte = byte | 1 else: byte = byte | 0 if ((i + 1) % 8 == 0): the_bytes.append(byte) byte = 0 return the_bytes def __calculate_checksum(self, the_bytes): return the_bytes[0] + the_bytes[1] + the_bytes[2] + the_bytes[3] & 255测量执行python程序： TemHumSensor.py
import dht11 import RPi.GPIO as GPIO import time GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) try: while True: instance=dht11.DHT11(pin=4) result = instance.read() print 'temperature'+str(result.temperature) print 'humidity'+str(result.humidity) time.sleep(2) except KeyboardInterrupt: pass