K210 环境检测.zip

import time from maix import GPIO from fpioa_manager import fm import time 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: def __init__(self, gpio = None): # '1DHT11 sensor reader class for MaixPy' if gpio != None: self._gpio = gpio else: raise Exception("please input a valid gpio") def read(self): self._gpio.mode(GPIO.OUT) # send initial high self.__send_and_sleep(1, 50) # pull down to low self.__send_and_sleep(0, 20) # change to input using pull up self._gpio.mode(GPIO.IN) # 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 # The meaning of the return sensor values # the_bytes[0]: humidity int # the_bytes[1]: humidity decimal # the_bytes[2]: temperature int # the_bytes[3]: temperature decimal temperature = the_bytes[2] + float(the_bytes[3]) / 10 humidity = the_bytes[0] + float(the_bytes[1]) / 10 return DHT11Result(DHT11Result.ERR_NO_ERROR, temperature, humidity) def __send_and_sleep(self, output, sleep): self._gpio.value(output) time.sleep_ms(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 = self._gpio.value() 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