Paul,
I now have a DS9490R USB driver and the DS1820 works fine, so its a timing
issue in my PIC code written in C from a Maxim app note. Someone has suggested
reducing the 4.7k pull-up resistor so I'll try that.
Thinking a bit more, maybe I should use one of the DS2480B driver chips instead
of bit-banging?
cheers
Paul
----- Original Message -----
From: Paul Alfille
To: owfs-developers@lists.sourceforge.net
Sent: Tuesday, December 26, 2006 12:40 AM
Subject: Re: [Owfs-developers] Unreliable DS1820?
On 12/25/06, Paul Hadley <[EMAIL PROTECTED]> wrote:
After a lot of failures and messing around, it did finally respond with a
presence pulse, temperature reading and a valid CRC. Warming the sensor with my
fingers showed the temp climb up a few degrees, then down again when released.
Wonderful I thought, until............. after possibly touching the 1-Wire it
suddenly stopped working permanently (no presence pulse).
Paul
Sounds unrelated to OWFS.
My experience is that the DS18x20 are quite robust. I've handled, dropped,
stepped on them without problems. There is an issue with negative voltages on
the data line, and the recommendation is to use a diode to protect them.
How to test? Ask for some more samples from Dallas, or try in another system,
like what you propose. If more than one failed at the same time, I'd also be
suspicious of the rest of your circuit or software.
Paul Alfille
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