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I have added 2 DS18B20 sensors to my Raspberry pi 1, both sensors shows up in /sys/bus/w1/devices and I can only read data from one of them, the other simply has a empty w1_slave file.

They are not both connected to the same pins, the working one is connected to GPIO14 and the one not working but listed is connected to GPIO17.

I have this in my /boot/config.txt file:

dtoverlay=w1-gpio,gpiopin=14
dtoverlay=w1-gpio,gpiopin=17

and I use this script to pull up the resistor:

import RPi.GPIO as GPIO

GPIO_PIN_NUMBER=17
GPIO.setmode(GPIO.BCM)
GPIO.setup(GPIO_PIN_NUMBER, GPIO.IN, pull_up_down=GPIO.PUD_UP)

There is 2 of those files where the other one has GPIO_PIN_NUMBER=14

In /sys/bus/w1/devices I see this:

28-00000003ae63  28-00000003c175  w1_bus_master1  w1_bus_master2

And the 28-00000003c175 is the working one which reports the temperature but the 28-00000003ae63 has the empty w1_slave file.

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  • I have tried swithing the non working to GPIO4 with same result, I have also tried switching the sensor to a new one, same result.
    – HDIK
    Commented Apr 7, 2022 at 14:32
  • Have you tried connecting both to GPIO 14 (1-wire is a bus) to check that both work?
    – joan
    Commented Apr 7, 2022 at 16:33
  • @joan, hello. Yes, I have tried that and if I use GPIO14 for both, they both works (not when both are connected tho) but one by one they both works. And I believe that, if the system can see the device, then it "should" work, but there most be sth I do wrong since the w1_slave file is empty.
    – HDIK
    Commented Apr 7, 2022 at 16:38
  • 1-wire is a bus. You can have multiple 1-wire devices connected to the same GPIO at the same time.
    – joan
    Commented Apr 7, 2022 at 16:40
  • Yes, I know that, but no matter how I do it or which raspberry version I use, then it doesn't work. and I only need these 2 sensors, so using 2 channels doesn't hurt I guess, since using same fails everytime.
    – HDIK
    Commented Apr 7, 2022 at 16:42

2 Answers 2

Reset to default
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I've found out that the cause of this is the cat6 cable I was using to extend the cable of the sensor, putting the sensor directly to the pin makes it works as should, so I just need to figure out what cable to use instead.

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1

Use a 3K to 4K resistor or something close, the added cable increases the capacitance slowing it down.

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1
  • Plus, Raspberry has inbuilt pull up which is more than enough.
    – HDIK
    Commented Apr 8, 2022 at 12:16

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