Hi Loren,
As I understand, you are using the w1 interface and Beaglebone Black, but
I'm not sure what the bus-master is. A gpio pin?
-62 is not familiar to me. How often does it happen, and does the system
continue to work with occasional glitches or does it need reset? Note that
w1 errors might be reported by the system (dmesg).
I have a BBB and can try to see if I get the same errors if you describe
your setup a little more.
Paul Alfille
On Sat, Jul 5, 2014 at 8:32 PM, Loren Amelang <lo...@pacific.net> wrote:
> My problem with 12-bit reads degenerating to half-degree steps seems to be
> hiding since I built a new system with Ubuntu 14.04. I've only seen a few
> individual readings that looked "stuck" at the previous value since then,
> never full days of half-degree steps.
>
> But I still get two kinds of rare, occasional errors. There are the
> expected 85C errors, and these:
> ---
> Thu Jul 03 2014 22:15:01 GMT-0700 (PDT)
> cd 01 4b 46 7f ff 03 10 4a : crc=4a YES
> cd 01 4b 46 7f ff 03 10 4a t=28812
> Thu Jul 03 2014 22:20:02 GMT-0700 (PDT)
> ff ff ff ff ff ff ff ff ff : crc=c9 NO
> cd 01 4b 46 7f ff 03 10 4a t=-62
> Thu Jul 03 2014 22:25:02 GMT-0700 (PDT)
> c9 01 4b 46 7f ff 07 10 64 : crc=64 YES
> c9 01 4b 46 7f ff 07 10 64 t=28562
> ---
> Fri Jul 04 2014 13:55:01 GMT-0700 (PDT)
> c8 01 4b 46 7f ff 08 10 3f : crc=3f YES
> c8 01 4b 46 7f ff 08 10 3f t=28500
> Fri Jul 04 2014 14:00:02 GMT-0700 (PDT)
> ff ff ff ff ff ff ff ff ff : crc=c9 NO
> c8 01 4b 46 7f ff 08 10 3f t=-62
> Fri Jul 04 2014 14:05:02 GMT-0700 (PDT)
> cc 01 4b 46 7f ff 04 10 67 : crc=67 YES
> cc 01 4b 46 7f ff 04 10 67 t=28750
> ---
>
> I've never seen -62 errors before. All of them I've captured in detail
> match the above pattern, where the first byte string is all 'ff', and the
> second byte string matches the previous valid temperature exactly.
>
> What could be happening there? If the "t=" value is being derived from the
> byte string to the left of it, it should be the correct temperature. But it
> is always -62.
>
> Why are there two lines of bytes? Are they separate reads?
>
>
> Apparently there are supposed to be "statistics" somewhere, but I don't
> seem to have any. Here is all I find:
> ---
> ubuntu@arm:/sys/devices/w1_bus_master1$ ls
> 28-0000008847d6 power w1_master_add w1_master_name
> w1_master_remove w1_master_slaves
> 28-000000884d88 subsystem w1_master_attempts w1_master_pointer
> w1_master_search w1_master_timeout
> driver uevent w1_master_max_slave_count w1_master_pullup
> w1_master_slave_count
> ---
>
> Maybe the w1 interface doesn't provide statistics?
>
>
> Am I missing some source of deeper documentation than the web site
> provides?
>
> Loren
>
> | Loren Amelang | lo...@pacific.net |
>
>
>
>
>
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Turn processes into business applications with Bonita BPM Community Edition
Quickly connect people, data, and systems into organized workflows
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