1-wire sensor not detected in Evok web interface

  • Apologies for the newb question.

    I am trying to use DS18B20 temperature sensors with an Axon L205 controller (using Evok and node-red). Currently I've got a single DS18B20 hooked up to the 1-wire port, and it doesn't show up in the web interface. I've tried connecting a couple of the sensors, none of them get detected.

    I am not sure what further steps to take to diagnose the cause of the problem. Have I skipped some required configuration steps? I see that the evok.conf file has example entries for 1-wire devices but I am not sure if these are supposed to be auto-generated or if I am supposed to create them myself. Is there some way to manually scan the 1-wire bus for available devices?

  • administrators

    Hi @clueless,
    just to be sure, can you please post some photos of your sensor connection?


  • @martin-kudláček
    The first batch of sensors I tested this with came with wires and a casing, so I just attached the wires straight into the connector.
    alt text

    Then I also tested ones that just came as components with pins by placing them on a breadboard (the arduino shield has no significance, I am only using the breadboard glued onto it) In one of the images you can see the testing jig I used to verify that the sensors are giving temperature measurements on the breadboard. I did continuity checks to verify that there is a connection between the connector screws and the pins of the sensor.
    alt text
    alt text

    I don't think it's a wiring issue. I suspect I might have messed something up during the installation of nodejs, npm and node-red, but I would like to know if there are some ways to diagnose the issue before trying something radical like reflashing the OS.

  • Hi @clueless!

    Do you see the other Axon inputs and outputs in the web interface, and if so, could you take a screenshot of it? The underlying stack for 1-Wire is quite simple - it consists of an OWFS server interface and an I2C 1-Wire adapter (with a device-specific hardware power switch, allowing it to be turned off/restarted independently of the rest of the system). While it is possible that the faulty behavior is due to a software issue, it's not the likeliest possibility in this case.

    If you could also provide the output of a "sudo dmesg" command from the Axon SSH console it could potentially help us see if there is anything further going wrong.

  • @tomasknot
    All the other outputs and inputs are visible, and activating digital outputs in the web interface triggers them (or their status indication diodes, anyway).

    I am not quite sure which parts of the dmesg output are relevant to the issue at hand so here is the entire thing:
    (EDIT: apparently I pasted two successive outputs, here's just one)

  • Unfortunately the kernel log output looks fine to me.

    Could you please post the contents of the SYSFS 1W folder '/sys/bus/w1/devices', i.e. ' sudo ls -la /sys/bus/w1/devices'? If you could also post the output of an 'lsmod' and 'ps fax' commands that would be very helpful as well, as I could then check if all the OWFS components are running correctly as well. I imagine they will be sizable, so a pastebin might be preferable again.

    Apologies for the long debugging steps, but it can be quite difficult to track down an issue like this, since there is a large number of things that can potentially go wrong. However we do test each of our units with standard DS18b20 thermometers before shipping, and your setup does seem correct.

  • @tomasknot
    Here's the 1w device folder:

    unipi@L205-sn7:~$ sudo ls -la /sys/bus/w1/devices
    total 0
    drwxr-xr-x 2 root root 0 Dec 11 16:08 .
    drwxr-xr-x 4 root root 0 Dec 11 16:07 ..


    unipi@L205-sn7:~$ lsmod
    Module                  Size  Used by
    ds2482                 16384  0
    unipi                  98304  6
    wire                   32768  1 ds2482
    industrialio           53248  1 unipi
    at24                   20480  0

    ps fax:

  • Ok, after failing to diagnose the issue I ended up reflashing the OS and connecting to the controller through Mervis. I was able to reach the sensor without changing anything about my physical setup, which leads me to believe it was something I had done wrong during the installation of nodejs - which is not at all unlikely, since I kinda bodged my way to it after finding that the standard scripts in the links given would not work.

  • Hi @clueless,

    Glad to hear it's working - I'm not sure what exactly could have gone wrong, as everything seemed to be okay in the logs, which left me, well, quite clueless.

    I was hoping to get back to you with some more information, but frankly could not think of any simple checks to be made. At any rate - I am very glad to hear that it is working for you now!

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