Hi Mick,
Thanks for the reply. I think I have the the source of the issue - it seems to
be related to the quality of the power to the 1-wire bus. Last night I tried
different things - soldering everything together, instead of using a breadboard
and connecting to a known-good bus with 10 devices. The result was still the
same - all devices were recognized by owfs, but the temperature was 127 degrees
on all 10 DS18B20's.
Then I changed the power supply to my Beaglebone from being powered over USB
from my Mac, to a standalone 5V DC/2A power supply, and the problem went away
The DS2483 is powered from the 3.3V and 5V VDD, from the Beaglone Black - this
means that the 1-wire bus is also powered from the same 5V source as the
Beagleboard
I didn't put a scope on the 5V supply, so I don't know if the level was too
low, or there's some noise on the 5V supply.
However, it seems it's possible to power the 1-wire bus in such a way, that the
devices responds correctly to queries from the bus master, but fails to convert
the measured temperature
- JAN
Tændt 8. nov. 2013 at 17.38.56, Mick Sulley ([email protected]) Skrev:
Apologies for not replying before, just noticed the post again.
The problem just went away, so I have no idea what caused or cured it.
Sorry I can't be more help
Mick
On 22/10/13 07:47, Jan Chrillesen wrote:
> On Thu, 25 Apr 2013, Mick Sulley <[email protected]> wrote:
>
>> No I have never changed it, just leave it as Centigrade. The strange
>> thing is that most of the readings are OK, around 19, 20 or so, but then
>> these odd ones at 127
>>
>> I will continue to monitor!
> (Replying to an old posting)
>
> Did you ever find a solution for this?
>
> I have just set up a Beaglebone Black with DS2483 and a single DS18B20,
> using owfs 2.9.1, and see the same behaviour (temperature always
> 127.938). I haven't yet tried to add more sensors
>
> - Jan
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