OK I have now reconfigured my system so that all the I/O modules are
individually powered rather than over the 1- wire cabling, which I am
hoping will improve reliability. Also all sensors are powered. Now to
get back to the other issues.
How do I set the resolution? Looking at the DS18B20 manual it says that
it is done via the scratchpad, but I have no idea how to do that. My
code is all python, so I guess I can write the necessary value to the
scratchpad at startup, but what do I write? The DS18B20 manual on
GitHub does not mention the scratchpad.
Thanks
Mick
On 19/02/2019 17:38, Jan Kandziora wrote:
Am 19.02.19 um 14:35 schrieb Mick Sulley:
The failure happened for about 10-20 minutes, reading about every 10
seconds or so, then it recovered and is reading fine again.
All devices are powered.
I could change my code so that it reads fasttemp and if that is 85 it
reads through the others to try to find a good read. Is that a sensible
thing to do?
What I recommend to do for preparation is:
* power all sensors
* set the sensor EEPROM to 9 bit default resolution.
Then, the readout thread is as follows:
1. trigger a 12-bit resolution conversion on each sensor for initialization.
2. write soemthing to /simultaneous/temperature to trigger all
temperature conversions at the same time.
3. wait a second
4. read /uncached/<sensorid>/latesttemp of each sensor
5. If the result for a sensor is not 85°C, store and go to 2.
6. 85°C. Check the resolution. If it is still 12 bit, that's a valid
reading. Store and go to 2.
7. Power-on-reset. Store an error. Trigger a 12-bit resolution
conversion for that sensor and go to 2.
Kind regards
Jan
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