The correct 5v step up buck converter will give your arduino constant power even when battery level drops, thus making reference voltage constant, if you take measurements from the battery terminal then it should work fine, even with your old code
Yes, that is what i want to do. Power the board by 5v constant converter while reading the voltage directly from battery terminal.
For now my lipo 3.7v is connected to TP4056 charger, and came out from it then connect to board, does is diatrupt anything? My voltmeter reads both in and out from TP4056 is the same voltage, so i assume no problem attach it right?
By saying my old code will work, and by looking at the library...it can read voltagr from A0 pin right?
Before using it i search for info, yes its originally for 18650 battery, googling found it can be use to charge LiPo too, i try and it works to charge it.
If not so, i just make a split wiring from battery terminal goes direct to what im doing, ignoring the charging module
I think you should read on safe charging discharging cycle of LiPo batteries since you are going to use them, and maybe about other types of batteries. Why you need specific voltage, what happens to the charge current, what happens when battery goes below its lowest limit, etc, etc. This knowledge will serve you in the future
not going to buy it, too expensive in my country LoL