Interfacing to 1-Wire LAN, especially Dallas temperature sensors?

[Brad Clements]

There is a technique where you can use a UART at some whacky baud rate and
bits/byte setting to communicate. There's an APPNOTE somewhere, I don't have
it handy.

--
Novell DeveloperNet Sysop #5

_
"Peter Hansen" <peter at engcorp.com> wrote in message
news:3CF82E8E.23C6FA10 at engcorp.com...
> Christian Aastorp wrote:
> >
> > I'm considering doing some temperature control and logging, both
> > enviromental and inside computers. Did a google search, and found
> > references to the range of temperature sensors from Dallas
> > Semiconductors.
> >
> > I also found schematics for interfacing with the serial port, and
> > timing diagrams for implementing 1-Wire Lan using direct control of
> > the port.
> >
> > As I'm using  Python for my programming, these days, I would like some
> > pointers to modules or techniques to use Python to read the
> > temperature sensors.
>
> Although I have not tried it with Python, and I would never say
> something is impossible without more study, I am _fairly_ sure you
> cannot do this reliably with Python.
>
> The Dallas 1-Wire chips have protocol timing requirements somewhere
> down in the low _tens_ of microseconds.  This requires some kind of
> real-time code and not only is Python itself unlikely to have
> high enough performance on almost any current machine, but the
> OS you're running it on is even less likely to support the
> necessary latency.
>
> We've been struggling just to get a 16MHz 68HC12 working with
> these things, without having to disable interrupts for hundreds
> of microseconds at a time.  It hasn't been easy.
>
> It might be very instructive to try, however, and I'd be happy
> to hear somebody say they'd proven me wrong (and curious what
> was done to reach a solution).
>
> -Peter




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