1-wire (draft)

1-wire - Community Recommended Pinout DRAFT 4th Feb 2015

1-wire is a bus protocol that requires only a single wire to communicate.

While the TRS form is defined below, you are recommended to always use the TRRS form instead over the TRS form (and leave the interrupt pin unconnected if necessary).

Cat3 phone sockets is also a good choice for longer connections.

Headers

2 pins


2 pins:
    [OWD][GND]

3 pins:
    [VCC][OWD][GND]

4 pins:
    [VCC][OWD][GND][AUX]

5 pins:
    [VCC][OWD][GND][AUX][INT]

7 pins:
    [5V][3.3V][VCC][OWD][GND][AUX][INT]

TIP : Power VCC
OWD : 1-wire RX/TX
GND : Ground 0V
AUX : Unregulated Power Input ( Typically Max 12V )
INT : Shared Interrupts

TRS


1-wire via TRS (Plug/Receptacle)

TIP    : Power VCC
RING1  : 1-wire RX/TX
SLEEVE : Ground 0V

This form supports 1-wire communication, as well as power to devices. Because it is a bus protocol, you can place these devices on the same line.

TTRS


1-wire via TRS plug (Plug/Receptacle)

TIP    : Power VCC
RING1  : 1-wire RX/TX
RING2  : Interrupt signal From slave to master
         [Recommendation: Add a resistor in case of a short to ground]
SLEEVE : Ground 0V

Justification/Reasoning For TTRS and TRS

Since we defined RING1 as RX/TX in the TRS form already, we want to place the interrupt pin in RING2 so that the TRRS 1-wire plug will still work in both the TRRS and the TRS receptacle.

Why is there no "Aux Power" to inject a higher unregulated voltage? Because there is a risk that during plugging, there would be a short on any pins. This may be fine for lower voltages like 5V, but dangerous for 12v.

Because 1-wire plugs will work on both TRS and TTRS 1-wire receptacles, it is important that a resistor is placed on the output of the interrupt pin of the slave device. This is because a TRRS plug plugged into a TRS receptacle, will have RING2 shorted to SLEEVE.

Modular Plug

6PxC : 6 pin telephone plug ( TIA/EIA-568 )


    RJ12 Telephone Based One-Wire Pinout:
    RJ12 (6P4C connector) (4 conductors)

                _____
              _|     |_
     ________|         |_________
    |                            |
    |                            |
    |                            |
    |__[][VCC][OWD][GND][AUX][]__|
           ^    ^    ^    ^ 
           4    3    2    1 

     Pin (Parasitic One Wire):
      Good for single pair phone cables
      * 3 : One Wire Data
      * 2 : GND 0V

     Pin (Powered One Wire):
      Good for 4 conductor telephone extension cables.
      * 4 : VCC Regulated ( disconnected by default )
      * 3 : One Wire Data
      * 2 : GND 0V
      * 1 : AUX Unregulated ( Typically Max 12V )

If you are willing to make your own cable (not easy to source):


    RJ12 Telephone Based One-Wire Pinout:
    RJ12 (6P6C connector) ( 6 conductors)

                 ______
               _|      |_
     _________|          |_________
    |                              |
    |                              |
    |                              |
    |[CON][VCC][OWD][GND][AUX][INT]|
       ^    ^    ^    ^    ^    ^ 
       6    5    4    3    2    1 

     Pin (Powered One Wire):
      Good for 4 conductor telephone extension cables.
      * 6 : CON Connected Indicator
      * 5 : VCC Regulated ( disconnected by default )
      * 4 : One Wire Data
      * 3 : GND 0V
      * 2 : AUX Unregulated ( Typically Max 12V )
      * 1 : INT Interrupt

     Note: 
        The CON pin, asserts a low pulse to indicate when 
        a device is connected and ready to operate.
        There is a pullup on the CON pin by the master. 
        For simple devices, this is via a small capacitance to ground.

     Question: Should CON be a pulsed assert low? Or just assert low?

8P8C: RJ45 (e.g. Ethernet Plug)


    One wire network via cat5 RJ45 Ethernet cable:
    (Pass through RJ45 cat5 cable)
                _____
              _|     |_
     ________|         |_________
    |                            |
    |                            |
    |                            |
    |[][][VCC][OWD][GND][AUX][][]|
     ^     ^    ^    ^    ^     ^
     8     6    5    4    3     1

     Pin (Powered One Wire):
      Good for 4 conductor telephone extension cables.
      * 8 : 5V
      * 7 : 3.3V
      * 6 : VCC Regulated ( disconnected by default )
      * 5 : One Wire Data
      * 4 : GND 0V
      * 3 : AUX Unregulated ( Typically Max 12V )
      * 2 : INT Interrupt
      * 1 : CON Connected Indicator

Justification/Reasoning

Most of the above design, allows for usage of common unmodified telephone or ethernet cables.

Typical 6P6C telephone conductors come in single pair (2 wires) and double pairs (4 wires). Since one wire at the minimum supports two conductive wires, best to arrange pins to allow for this.

For the full 4 conductive wires cable, best to use the two pins for power. One for 5V, since one wire devices rarely require more than 5V (some may be even 3.3V). And another for AUX power input, this is intended for sending higher voltage DC input (To be regulated down to device voltage internally), to account for
resistive losses over the length of an extended line.

As for the 8P6C, the wiring pattern was chosen to allow for usage of unmodified ethernet cable. In most cases however, its easier to use the telephone 6PxC version.

Source For This Pin out (Thanks to Ned):

Modifications @ Jan 2015:

  • swapped around TRS and TRRS pinout to more closely match DS18S20 pinout (Thus making PCB breakout design simpler).

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