The Python program deals with any failed messages and reports the temperature in degrees C and F every second.
# SPDX-FileCopyrightText: 2019 Mikey Sklar for Adafruit Industries
#
# SPDX-License-Identifier: MIT
import glob
import time
base_dir = '/sys/bus/w1/devices/'
device_folder = glob.glob(base_dir + '28*')[0]
device_file = device_folder + '/w1_slave'
def read_temp_raw():
f = open(device_file, 'r')
lines = f.readlines()
f.close()
return lines
def read_temp():
lines = read_temp_raw()
while lines[0].strip()[-3:] != 'YES':
time.sleep(0.2)
lines = read_temp_raw()
equals_pos = lines[1].find('t=')
if equals_pos != -1:
temp_string = lines[1][equals_pos+2:]
temp_c = float(temp_string) / 1000.0
temp_f = temp_c * 9.0 / 5.0 + 32.0
return temp_c, temp_f
while True:
print(read_temp())
time.sleep(1)
The next three lines, find the file from which the messages can be read.
def read_temp_raw():
catdata = subprocess.Popen(['cat',device_file], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out,err = catdata.communicate()
out_decode = out.decode('utf-8')
lines = out_decode.split('\n')
return lines
Reading the temperature takes place in two functions, read_temp_raw just fetches the two lines of the message from the interface. The read_temp function wraps this up checking for bad messages and retrying until it gets a message with 'YES' on end of the first line. The function returns two values, the first being the temperature in degrees C and the second in degree F.
You could if you wished separate these two as shown in the example below:
deg_c, deg_f = read_temp()
The main loop of the program simply loops, reading the temperature and printing it, before sleeping for a second.
To upload the program onto your Raspberry Pi, you can use SSH to connect to the Pi, start an editor window using the line:
nano thermometer.py
and then paste the code above, before saving the file with CTRL-x and Y.
