Easy MG24 battery measurement

[msfujino]

This method uses the default AD converter settings, Vref=3.3V(VDD), analogGain=1. With this method, battery voltage cannot be measured in the range of approximately 3.4V or lower.

To measure down to the range below 3.4V is discussed in the following link

XIAO_MG24 battery voltage measurement function is not available

The XIAO_MG24 has the ability to measure battery voltage by dividing it by 1/2. Assuming the maximum battery voltage is 4.2V, the full scale of AD conversion requires at least 2.1V. The reference voltage Vref can be selected from the internal reference voltage of 1.2V or VDD (3.3V). When Vref=1.2V is selected, battery voltages above 2.4V cannot be measured. When Vref=VDD(3.3V) is selected, battery voltage below 3.3V cannot be measured because VDD drops below 3.3V. On the other hand, the MG24 c…