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, [EMAIL PROTECTED] <[EMAIL PROTECTED]> 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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