DS18B20 Temperature sensor

Question

Currently I can read the temperature reading from a file for both sensor. import os import time

os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

temp_sensor = '/sys/bus/w1/devices/28-0316004f1fff/w1_slave'

def temp_raw():
  f = open(temp_sensor,'r')
  lines = f.readlines()
  f.close()
  return lines

def read_temp():
  lines = temp_raw()
  while lines[0].strip()[-3:] != 'YES':
    time.sleep(0.2)
    lines = temp_raw()
  temp_output = lines[1].find('t=')
  if temp_output != -1:
    temp_string = lines[1][temp_output+2:]
    temp_c = float(temp_string)/1000.0
    return temp_c

while True:
  print(read_temp())
  time.sleep(1)

Now I am trying to read two sensors at once but have no idea how to do it.

Answer 1

You are now only looking for a single slave device (/sys/bus/w1/devices/28-0316004f1fff/w1_slave), but you ought to also look at the other /sys/bus/w1/devices/28*/w1_slave device.

Better try something like:

#!/usr/bin/python

import sys
import glob

sensors = glob.glob("/sys/bus/w1/devices/28*/w1_slave")

for sensor in sensors:
  tfile = open(sensor)
  text = tfile.read()
  tfile.close()
  secondline = text.split("\n")[1]
  temperaturedata = secondline.split(" ")[9]
  temperature = float(temperaturedata[2:])/1000
  print "sensor", sensor, "=", temperature, " degrees."

Answer 2

You can get a list of all the one-wire sensors from the w1_master_slaves file.

def get_slaves():
    """Return the IDs for all one-wire sensors available to the system."""
    slaves = []
    slaves_file = '/sys/bus/w1/devices/w1_bus_master1/w1_master_slaves'
    with open(slaves_file, 'r') as f:
        slaves = [slave.strip() for slave in f]
    return slaves

For example:

>>> get_slaves()
['28-000004d12260', '28-000004d01bf3']

Then use these ids to open the specific device files.