App note: Advanced 1-Wire Network Driver

Posted on Saturday, December 31st, 2011 in app notes by DP

This reference design shows how to drive long 1-Wire networks. 1-Wire is a communications protocol used by some Dallas/Maxim parts. The protocol uses only one wire for power, transmission, addressing, and synchronization.

This document describes a microcontroller-based 1-Wire master interface for reliable operation of small, medium size and large 1-Wire networks. This is accomplished using careful impedance matching, intelligent (software-controlled) active pullup, and slew-rate control. Software flow charts are included to assist the user in generating the correct 1-Wire timing for reset pulse, presence detect, write one, write zero and read time slots using any suitable microcontroller. Scope traces illustrate the timing performance of the driver as well as transmission line effects as they appear with long cables.

We think 1-Wire’s days are numbered because Maxim has discontinued most 1-Wire parts. Maybe if they didn’t prohibit 3rd-party slave devices it would have seen wider use…

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3 Responses to “App note: Advanced 1-Wire Network Driver”

  1. Greenmayo says:

    I had few exchanges with Maxim’s staff regarding this discontinuity issue. For me, they’re only interrested in securtity and authentification market for these products. In my opinion, if someone is good enough to programm a PIC12 as multipurpose 1-wire slave, they’ll only complain that it might have the same Rom ID as one of theyr genuine slaves. But some manufacturers already do theyr own 1-wire slave. I don’t know if it’s done under Maxim’s licence (hope them to…), but sold me some sensors with a pic 24F16KA as 1-wire slave (but I assume this function can be done by a cheaper and smaller chip).
    As you can see here : a lot of peoples are upseted byt discontinuity of 1-wire devices. Last point MAXQ1004 is a microcontroller integrating a 1-wire slave interface. Maybe a solution ?

    • David C says:

      I’m with Embedded Data Systems. We are currently (and have been since 2011) using 1-Wire ROMs licensed from Maxim within the “7E” family code range.

  2. Thomas W. says:

    Oh. I thought the DS18S20 was alive and kicking. First the NSLU2 and then 1-Wire. I find myself into vintage hardware all of a sudden. What is going to replace 1-Wire?

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