Which DATA LINE? Using Six 1wire temp sensor with unipi hub and Raspberry Pi (GPIO 4)



  • Today I bought six Unipi 1Wire temperature sensors DS18B20 with RJ45 Plug and one Unipi Hub as seen on: https://www.unipi.technology/hardware_documentation/1-wire-network-46

    My questions:
    Manual says the temperature sensor DS18B20 has two data lines 6 and 7 and should both be used.
    When I use the hub with a Raspberry Pi (on GPIO4) which data line should I use, outgoing from the hub to the Raspberry (GPIO4)?
    I don’t want to blow up something………….

    Furthermore explanation says:
    The 1-Wire bus in all UniPi devices does not use just one wire, but it uses two data lines to serialize the network in order to maintain maximum reliability ..........
    AND: it is necessary to follow the right order when connecting sensors (or other HUBs) as shown in the following pictures (mentioned in the URL above)……………..
    AND: it is required to connect both data lines 6+7 and of course lines 5 (Vcc - 5V) and 8 (GND).......

    Answer on this forum:
    Basically it will work if you connect only the pin 6 of rj45 to your DS12B20 DQ line but if you are using any of our hub or 1wire devices you will break the 1wire bus if you do not connect the pin 7 too.

    Thus this mean that i can not use the Unipi hub?

    Where should I put my 4.7k resistor??

    Thnxs for your help!

    Evert T.



  • Dear Administrator or visitor(s)......I think I have the answer myself!

    Is this drawing my answer of my questions?

    From Raspberry to port 1 on the unipi hub, using:
    HUB pin5 to Raspberry pin3 (VCC 3,3 V)
    HUB pin6 to Raspberry pin7 (GPIO4) and
    HUB pin8 to Raspberry pin6 (Ground)

    My six 1wire temp sensor on port 2-7 ???

    0_1522150933292_schema.jpg

    The resistor of 4.7k~ 10k, between pin 3 and pin 7 on the Raspberry??

    Thnxs,

    Evert T.


  • administrators

    Hi Evert!

    We only provide official support for using the 1Wire Hub with standard-compliant 1Wire masters.

    While it may be possible to turn the RPi into one, our Neurons use a dedicated 1Wire master PCB, which in particular is powered via a discrete 24V-in/2-3.3-5-12-24 out PSU.

    In principle what you are asking to do may be possible, but unfortunately we cannot provide any guarantees or instructions.

    Perhaps some of our other users here on the forum might be able to help.


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