[AE-74] Revamp Battery API for Nicla Sense ME

[sebromero]

Change log

🐛 Fixed Bugs

• Fixed the incorrect calculation of the battery voltage percentage.
• Fixed incorrect voltage reading by adding a tiny delay to give the chip time to wake up from High Impedance mode.
• Fixed a slightly incorrect interpretation of the NTC values (introduced a new state 'Extreme' which indicates the charging has been suspended).
• Fixed edge case in the charging current setting that could cause an external value to be used instead of a programmatic one.
• Fixed incorrect TS and interrupt disable in enableCharging function
• Fixed an issue that would prevent the battery charge percentage from being updated continuously.
• Fixed a bug that would constrain the charge current setting due to the 8 bit data type.

🚀 Enhancements

• Added documentation to all functions related to power management.
• Added error handling to catch error cases
• Introduced Enums for battery charge level, temperature and operating status.
• Avoided high impedance mode when connected through VIN to to correctly report charging status
• Improved accuracy of battery voltage reading (disable charging while reading)

🆕 New Features

• Implemented a WebBLE based battery monitor + sketch for easy testing without external power supply
• Remove battery status function and replace with temp and charge level.
• Added function for toggling battery NTC.
• Added API for operating system status (e.g. charging).
• Added API to set regulated battery voltage.
• Added function to determine power source
• Added function to disable charging state
• Added function to configure the charging safety timer (30 min, 3h, 9h, disabled).
• Added sketch to demonstrate how to charge the battery and simply display the charging state.

[manchoz]

LATM – Looks Awesome To Me

[aliphys]

LATM!

😃 Nicla - PC WebBLE communication works as described.
😃 Connection is stable, even after several hours
😃 Battery graphic is cute / informative

😔 Reported battery voltage differs between WebBLE interface (3.86V) and scope

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• Webpage running locally on Chrome in Ubuntu 22.04. Voltage reported as 3.86V
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• Voltage between VBAT pin and USB ground is 3.32V
  • 
  • 

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This difference could be due to internal resistance of the ground plane.

[sebromero]

@aliphys Found another bug and fixed it. Basically the battery reading was not done correctly so it would only ever use what is measured when you plug it in.

[sebromero]

@facchinm
Some observations:

• 📖 A write operation was gonna be used to kick the watchdog previously, however the way it was implemented didn't seem to trigger a write operation. Conclusion: A read operation seems to be enough to reset the watchdog timer.
• ⚡ Battery seems to charge even when NTC settings are enabled but the battery doesn't have one. Conclusion: Accidentally enabling NTC on a non-NTC battery doesn't prevent it from being charged.
• 🔋 If the battery doesn't have an NTC, the speed is automatically reduced to 16mA no matter the setting. This one may need some more investigation. See nicla-system: Enhance documentation for charging speed limits. #685
• 🐶 The Watchdog mechanism seems to be redundant now after reworking the library:
  • The watchdog is disabled in High-Z mode. Now, by default the PMIC doesn't ever leave High-Z mode when powered through VIN (CD only used to toggle the charging). When powered with a battery it only leaves it very shortly to read some bytes from the PMIC within the 50s timeout of the watchdog. The new disableCharging() function was implemented by modifying a register, not by using CD. Conclusion: We could probably delete all code related to the watchdog timer.

That aside, I think I'm done here. Waiting for @aliphys ' green light 🟢

[aliphys]

LGTM. Thanks for the detailed PR and comments: we should try to strive for this level of quality.
Battery voltage updates correctly 👍