Hmm,
My guess is that they had customers that wanted fully compatible (even to
the family code) but with a slightly different feature set.
The temperature alarm functions are gone (but were hard to use as has been
pointed out -- you have to perform a temperature measurement to sense if
the value is out of bounds so you might as well test that directly).
Some memory, lockable, is included. I'd guess id or calibration.
The speed has been increased enough that the lower resolutions are no
longer needed.
Multiplexing variations on the same family code is a nuisance for OWFS, but
not much worse that the various humidity versions of the DS2438. In this
case it looks like there is a software way to distinguish the chips.
Paul Alfille
On Sat, Jul 14, 2012 at 10:22 PM, Gregg Levine <[email protected]>wrote:
> On Sat, Jul 14, 2012 at 9:29 PM, Paul Alfille <[email protected]>
> wrote:
> > Tell me about the MAX31826 not showing up. Any 1-wire device should show
> up
> > -- at least by address.
> >
> > Did you really not see a 3B.xxxxxx device? That suggests a connection
> > problem.
> >
> > As for the configuration register, the datasheets say:
> >
> > DS1825:
> > 0 R1 R0 1 AD3 AD2 AD1 AD0
> > MAX31826:
> > 1 1 1 1 AD3 AD2 AD1 AD0
> >
> > Thus the high-order bit seems to be different.
> >
> > On Sat, Jul 14, 2012 at 7:31 PM, Jeff Siddall <[email protected]> wrote:
> >>
> >> On 07/14/2012 09:57 AM, Paul Alfille wrote:
> >> > The support for the MAX31826 is complete, except I've run into a snag:
> >> >
> >> > The MAX31826 has 12-bit resolution and 128byte of memory
> >> > The DS1825 has 9-12 bit resolution and temperature alarm limits and no
> >> > memory
> >> >
> >> > Both have family code 3B and both have the adjustable address.
> >>
> >> I thought about this a bit more and now I am a bit puzzled. If they
> >> both look similar on the bus then I wonder why the MAX31826 did not show
> >> up in OWFS when I connected it to the bus? Whatever it is, perhaps you
> >> can leverage that to distinguish the MAX31826 from other family 3B
> >> devices.
> >>
> >> Jeff
>
> Hello!
> It's possible, Jeff, Paul, and Roberto, that when Maxim was planning
> the DS1825 and its related family of parts, other thermal sensors like
> it, they included expansion areas in the registers for the way the
> MAX31826 works. Which suggests that the MAX31826 is a superset of the
> DS1825 and even the others that the DS1825 is from.
>
> Further tests are necessary.
> -----
> Gregg C Levine [email protected]
> "This signature fought the Time Wars, time and again."
>
>
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