DS3231: Add calibration, temperature, and force_conversion #27
Conversation
This device has a temperature sensor with 0.25C precision, and an "aging offset" which can be used to calibrate the crystal frequency for increased timekeeping accuracy. Expose these as properties. This requires adafruit/Adafruit_CircuitPython_Register#39 as the temperature and calibration registers hold signed values.
| return self._temperature / 4 | ||
|
|
||
| def force_conversion(self): | ||
| """Forces a conversion and returns the new temperature""" |
There was a problem hiding this comment.
conversion seems a bit vague. Is there a more detailed way of describing it? I expected it to be force_temperature_conversion but then calibration calls it.
There was a problem hiding this comment.
I'll rework this a bit and rename it. (the checking for conversion-completed is wrong too) It is forcing a temperature conversion, which is necessary for the new oscillator calibration to become effective.
Datasheet says:
Bit 5: Convert Temperature (CONV).
Setting this bit to 1 forces the temperature sensor to convert the temperature into digital code and execute the TCXO algorithm to update the capacitance array to the oscillator.
This can only happen when a conversion is not already in progress. The user should check the status bit BSY before forcing the controller to start a new TCXO execution.
A user-initiated temperature conversion does not affect the internal 64-second update cycle.
A user-initiated temperature conversion does not affect the BSY bit for approximately 2ms.
The CONV bit remains at a 1 from the time it is written until the conversion is finished, at which time both CONV and BSY go to 0. The CONV bit should be used when monitoring the status of a user-initiated conversion
and explains why triggering a conversion after setting the calibration value ("aging offset") is useful:
The offset register is added to the capacitance array during a normal temperature conversion, if the temperature changes from the previous conversion, or during a manual user conversion (setting the CONV bit). To see the effects of the aging register on the 32kHz output frequency immediately, a manual conversion should be started after each aging register change.
`
Updating https://github.com/adafruit/Adafruit_CircuitPython_DS3231 to 2.4.0 from 2.3.2: > Merge pull request adafruit/Adafruit_CircuitPython_DS3231#27 from jepler/calibration-and-temperature Updating https://github.com/adafruit/Adafruit_CircuitPython_PCF8523 to 1.5.0 from 1.4.2: > Merge pull request adafruit/Adafruit_CircuitPython_PCF8523#19 from jepler/calibration-registers Updating https://github.com/adafruit/Adafruit_CircuitPython_PM25 to 1.0.2 from 1.0.1: > Merge pull request adafruit/Adafruit_CircuitPython_PM25#3 from dglaude/patch-1 Updating https://github.com/adafruit/Adafruit_CircuitPython_PyPortal to 3.3.0 from 3.2.5: > Merge pull request adafruit/Adafruit_CircuitPython_PyPortal#82 from fede2cr/master Updating https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT to 3.2.2 from 3.2.1: > Merge pull request adafruit/Adafruit_CircuitPython_MiniMQTT#44 from 2bndy5/master Updating https://github.com/adafruit/Adafruit_CircuitPython_ProgressBar to 1.3.0 from 1.2.3: > Merge pull request adafruit/Adafruit_CircuitPython_ProgressBar#8 from FoamyGuy/performance_boost Updating https://github.com/adafruit/Adafruit_CircuitPython_Requests to 1.5.0 from 1.4.3: > Merge pull request adafruit/Adafruit_CircuitPython_Requests#29 from brentru/update-cellular-3g
This device has a temperature sensor with 0.25°C precision, and an "aging offset" which can be used to calibrate the crystal
frequency for increased timekeeping accuracy.
Expose these as properties.
This requires adafruit/Adafruit_CircuitPython_Register#39 as the temperature and calibration registers hold signed values.
With these changes, I was able to use a precision frequency meter to "tune" the RTC so that it would have less than .01 seconds per day of error at 27°C, by assigning the best value to the calibration register.