I ran into this advertisement for a book that apparently has instructions on building a PIC 1-wire slave:
http://www.microengineeringlabs.com/products/books/scbook.htm
Serial Communications Using PIC® Microcontrollers - $49.95
by Roger Stevens
Copyright 2007
microEngineering Labs, Inc.
Box 60039
Colorado Springs CO 80960
(719) 520-5323
(719) 520-1867 fax
email: support <at> melabs.com

4. I've proposed adding 1-wire slave capabilities to a Maxim microprocessor (a sure win in my opinion) with no response.

> > E. Although Dallas is phasing them out, the DS2404 has dual inputs -- 1-wire
> > and 3-wire and can serve as a bridge to the PIC.
> >

Dallas is no longer manufacturing the 2404; the website suggests that
you won't get any unless you already use them in legacy hardware.

On website at http://owfs.org/index.php?page=hydroelectric-plant (I've included my responses).

---------- Forwarded message ----------

On Dec 13, 2007 3:44 PM, Hakan.Elmqvist <at> ki.se <hakelm <at> ki.se> wrote:

I have an old and small hydroelectric powerplant
( http://sundsvik.dnsalias.org/) run on a shoestring budget.
It is remotely monitored  and controlled by a
system mainly based on 1-wire devices using OWFS.

 

Thankyou for a very nice piece of software.
The 1-wire devices have their limitations, they
are for instance not very good at measuring
precise intervals and totals and other things.
Therefore I would like to design a flexible
device based on a microcotroller for instance a
PIC that can draw on the advantages of the 1-wire
protocol and extend the capabilities of the devices offered by Maxim.
The device to emulate that first comes to my mind
is the DS18S20 which has a rather simple
architecture with a read/write scratchpad memory
area which is ideal for my purposes.
My questions to you are:
1) Commands 0xBE and 0x4E: Can I in any simple
way read and write whole or parts of the
scratchpad memory with OWFS? Is there a
one-to-one relationship between the reported
temperature and the content of the temperature registers?

Well, we read scratchpad internally, and it would be easy to make it externally visible.
I don't currently, because it might overwhelm new users, and changing the scratchpad would make other aspects inaccurate (like temperature resolution).

2) Are you aware of any project for emulating the
Dallas 1-wire devices? I hate to reinvent the wheel.

Louis Swart's LCD uses a PIC to emulate a 1-wire device. Maxim in general is protective of the 1-wire device technology (for the slaves, the masters are fair game).

A. Have you looked at the DS27xx chips? They have temperature, current, accumulators, timers, voltages, even a bit of memory. Pretty cheap. Look specifically at the DS2760 DS2751 DS2770 and DS2780

B. There is no reason to blindly emulate the DS1820 -- we can create an entry to your chip using the command codes you like. It has to speak 1-wire (reset, selection, etc) but the actual protocol needn't be constrained.

C. If you really want to be different, we can make a unique adapter and chips that don't have to talk true 1-wire between them. We can work to make it fall generally in the same scheme.

D. There might be other resources (smart people) if you ask this question ion the owfs-developer's list.

E. Although Dallas is phasing them out, the DS2404 has dual inputs -- 1-wire and 3-wire and can serve as a bridge to the PIC.

 

Thanks in advance
Håkan Elmqvist

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