Is there a way only from the analog input where measure the battery voltage to distinguish that battery is charging?
I am short on IOs and will be quite a challenge to find extra input to hook a charging signal from the charging IC or the USB connector 
Thanks
Hello,
Which device are you working with?
The SAADC may measure the VDD bus directly through configuring the channel to measure VDD or VDDHDIV5.
This will not require any external routing or wiring. You can try this in the SAADC example by changing the channel configuration set with NRFX_SAADC_DEFAULT_CONFIG_SE to use the SAADC input NRF_SAADC_INPUT_VDD instead of _AIN0.
Best regards,
Karl
Hello, The device is nRF52840, but the problem is that between battery and nRF I have an external 3.3V voltage regulator. The only direct connection between the battery (LiIon 3.7V) is the voltage divider that is hooked to AI0, so I was interested if there is some algorithm that by just only reading analog input can distinguish if battery is charging or is full (4.2V)? My charging chips are MCP73831 or bq24092.
Thanks
Hello again,
samsam said:The device is nRF52840, but the problem is that between battery and nRF I have an external 3.3V voltage regulator.
Thank you for clarifying, this is very helpful to know.
samsam said:The only direct connection between the battery (LiIon 3.7V) is the voltage divider that is hooked to AI0
How is this voltage divider connected to your AIN0 pin?
Please be advised that the absolute maximum rating for voltage on the I/O pins with VDD < 3.6 V is VDD + 0.3 V, so if you are letting the battery's 3.7 V directly to the AIN0 pin these limits are exceeded and might permanently damage the chip.
samsam said:so I was interested if there is some algorithm that by just only reading analog input can distinguish if battery is charging or is full (4.2V)? My charging chips are MCP73831 or bq24092.
Yes, but this will depend on how your analog input is wired to your battery circuit. You could then measure how the voltage of the battery changes over time, and use this to deduce what the charger is doing.
Better yet, I skimmed quickly through the MCP73831 datasheet, and it seems to me that it comes with a Charge Status Output feature that can be used to determine the current state of the charging.
Have you looked into making use of this for your application?
Best regards,
Karl
Hello again,
samsam said:The device is nRF52840, but the problem is that between battery and nRF I have an external 3.3V voltage regulator.
Thank you for clarifying, this is very helpful to know.
samsam said:The only direct connection between the battery (LiIon 3.7V) is the voltage divider that is hooked to AI0
How is this voltage divider connected to your AIN0 pin?
Please be advised that the absolute maximum rating for voltage on the I/O pins with VDD < 3.6 V is VDD + 0.3 V, so if you are letting the battery's 3.7 V directly to the AIN0 pin these limits are exceeded and might permanently damage the chip.
samsam said:so I was interested if there is some algorithm that by just only reading analog input can distinguish if battery is charging or is full (4.2V)? My charging chips are MCP73831 or bq24092.
Yes, but this will depend on how your analog input is wired to your battery circuit. You could then measure how the voltage of the battery changes over time, and use this to deduce what the charger is doing.
Better yet, I skimmed quickly through the MCP73831 datasheet, and it seems to me that it comes with a Charge Status Output feature that can be used to determine the current state of the charging.
Have you looked into making use of this for your application?
Best regards,
Karl
