import RPi.GPIO as GPIO
import time
def bin2dec(string_num): # define a function to convert a binary number to a decimal.
return str(int(string_num, 2)) # return the string representing the integer value of the string passed to this function in base 2 (binary)
data = [] # define a data array
GPIO.setmode(GPIO.BCM) # use the Broadcom numbers instead of the WiringPi numbers
GPIO.setup(4,GPIO.OUT) # Set it as an output so that we can:
GPIO.output(4,GPIO.HIGH) # write a 1
time.sleep(0.025) # for 25 ms
GPIO.output(4,GPIO.LOW) # then write a 0
time.sleep(0.02) # for 20 ms.
I assume that the preceding sequence is the method to get the DHT sensor to respond with the current data.
GPIO.setup(4, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Change the pin to read mode, with a pullup resistor
for i in range(0,500): # 501 times
data.append(GPIO.input(4)) # read a bit from the GPIO, as fast as possible (no wait)
bit_count = 0
tmp = 0
count = 0
HumidityBit = “”
TemperatureBit = “”
crc = “”
try: # do this unless there’s an error. If there’s an error jump to “Except:”
while data[count] == 1: # as long as you read a 1
tmp = 1
count = count + 1 # count how many 1s have been read
for i in range(0, 32): # do this 33 times
bit_count = 0 # reset the bit count each time
while data[count] == 0: # as long as a 0 is read
tmp = 1
count = count + 1 # move on to the next bit
while data[count] == 1: # as long as a 1 is read
bit_count = bit_count + 1 # count how many 1s in a row
count = count + 1 # move on to the next bit
if bit_count > 3: # if there were mote than 3 * 1-bits in a row
if i>=0 and i<8: # if we're in the first byte
HumidityBit = HumidityBit + "1" # append a 1 to the humidity bitstring
if i>=16 and i<24: # if we're in the 3rd byte
TemperatureBit = TemperatureBit + "1" # add a 1 to the temperature bitstring
else: # if there weren't at least 3 * 1-bits
if i>=0 and i<8: # if we're in the first byte
HumidityBit = HumidityBit + "0" # append a 0 to the humidity bitstring
if i>=16 and i<24: # if we're in the 3rd byte
TemperatureBit = TemperatureBit + "0" # append a 0 to the temperature bitstring
except: # if there was an error in the “try:” block
print “ERR_RANGE” # report it
exit(0) # end the program
try: # do this unless there’s an error. If there’s an error jump to “Except:”
for i in range(0, 8): # do this 9 times
bit_count = 0 # reset the bit counter
while data[count] == 0: # as long as a 0 was read
tmp = 1
count = count + 1 # move on to the next bit
while data[count] == 1: # as long as a 1 was read
bit_count = bit_count + 1 # count how many 1s
count = count + 1 # move on to the next bit
if bit_count > 3: # if there were at least 3 * 1-bits
crc = crc + "1" # add a 1 to the crc (Cyclic redundancy check) bitstring
else: # if there were less than 3* 1-bits
crc = crc + "0" # add a 0 to the crc bitstring
except: # if the “try:” block failed
print “ERR_RANGE” # report it
exit(0) # end program
Humidity = bin2dec(HumidityBit) # convert the binary bitstring to a decimal variable for humidity
Temperature = bin2dec(TemperatureBit) # convert the binary bitstring to a decimal variable for temperature
if int(Humidity) + int(Temperature) – int(bin2dec(crc)) == 0: # test whether the CRC indicates that the reading was good
print Humidity # duh
print Temperature # duh
else: # if the CRC check was bad
print “ERR_CRC” # report it
looks like there should be an “exit (0)” here that’s missing. The program ends either way though. Usually the exit value indicates whether the program completed successfully.
POSTECH 78 stairs Piano Project 