1Wire topology



  • Hello experts,
    @ this site:
    http://unipi.technology/wiki/1Wire_topology
    you explain "...This means that at the end device (e.g. thermometer or any other 1Wire IC - 18B20, DS2408,...) you have to connect the DQ line to both 6 and 7 pins of the RJ45 connector in order not to split the topology. "

    Unfortunately there is no drawing and we understand this as a new wiring style. We suggest you mean a closed loop at the end of 4th DS18B20. This would be new to us especially if you use the original 1-wire-Master DS2480-100 of Maxim, which delivers sufficient resources (integrated timing).

    Our drawing shows only wiring the DQ-Line (=Data-Line). GND and +-line are not @drawing.

    Start@DS2408
    |
    |–-------Pin6–----DS18B20-----------DS18B20-----------DS18B20-----------DS18B20–--|
    |---------Pin7–----------------------------------------------------------------------------------| Data Line closed here?

    Could you explain your idea more exactly?
    With best regards
    iot



  • Hello experts,
    @ this site:
    http://unipi.technology/wiki/1Wire_topology
    you explain "...This means that at the end device (e.g. thermometer or any other 1Wire IC - 18B20, DS2408,...) you have to connect the DQ line to both 6 and 7 pins of the RJ45 connector in order not to split the topology. "

    Unfortunately there is no drawing and we understand this as a new wiring style. We suggest you mean a closed loop at the end of 4th DS18B20. This would be new to us especially if you use the original 1-wire-Master DS2480-100 of Maxim, which delivers sufficient resources (integrated timing).

    Our drawing shows only wiring the DQ-Line (=Data-Line). GND and +-line are not @drawing.

    Start@DS2408
    |
    |–-------Pin6–----DS18B20-----------DS18B20-----------DS18B20-----------DS18B20–--|
    |---------Pin7–----------------------------------------------------------------------------------| Data Line closed here?

    Could you explain your idea more exactly?
    With best regards
    iot



  • Hello,
    unfortunately there is no answer to this important topic.
    But the new picture on top of http://unipi.technology/wiki/1Wire_topology shows the normal bus-wiring from master to some slaves. The Pin 6/7 wiring is only used at the slave lines (the so called "stubs") to avoid long wiring away from the main bus line. This makes the 1w-bus more stable because there is only minimal stub-length (pin-length of DS18B20).

    So our mistake was to confuse the DS2408 with the DS2480 which ends in thinking that a 1w-master could have the Pin6/7 connection. This is definitely false and if the "slaves" at new picture will be completed with DS18B20 (thermo) and DS2408 (8-fold adressable switch) and the master at starting point with e.g. DS2480 everything would be clear.

    Your perfect wiring scheme with full linear topology is same like here. (see last section - Topologie - middle and right picture)
    http://www.fhemwiki.de/wiki/1-Wire_Busverlegung
    iot



  • I have existing 1-wire sensors that are wired up combining the dq and vcc, then the ground is seperate. Is there a way to make it work with the unipi?



  • I do not understand what do you mean by 'combining dq and vcc and separate ground' - do you mean that you use parasitic power? All of our sensors are are using separate power 5V on the VCC line, and separate DQ and GND. However if you have a working 1wire network you might only need to connect it to the UniPi (take a look at the documentation above) and everything should work well.