On 12/6/06, Paul Alfille <[EMAIL PROTECTED]> wrote:
> Perhaps there are some hints here.
>  You are using external power (non-parasytic) and a DS18S20?

No, some of the DS18S20's are parasitic some are not.  Only 2 are
throwing the error. If I remember correctly one is parasitic and one
isn't


>  The code is supposed to lock the device  (use a mutex to exclude other
> threads from that chip) issue a CONVERT command, wait 1sec, then read
> results. If it's functioning correctly, the only reason that 2 threads
> should create a problem would be the increased frequency of temperature
> conversions. Perhaps there is a rest time needed?
>
>  Can you run a type loop on a single thread reading one chip and see if you
> get an error?
>

Tight loop? The way I was doing my test was reading 4 sensors in a
tight loop and then starting another process to read the same sensors.
I'll modify the script to just hammer one of the sensors that throws
the error.

>  The other thought is that multiple simultaneous reads causes sags in the
> power line that occasionally interfere with readings. In that case 2
> threads, each in a tight loop, each reading a different temperature sensor
> would show an error.
>
>  Paul Alfille



-darryl
-- 
http://randomthoughts.vandorp.ca

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