TP4056 lithium battery charger with a switchable output between 3.3v and 4.2v (Battery volage). The LDO only draws 50uA (instead of others which are normaly used in Arduinos and so on with around 10mA), so the battery will last much longer. I build this to run my NodeMCU directly via 3v3 PIN instead of VIN. VIN or USB goaes via the onboard LDO which is a pretty bad one, it draws around 10mA for the conversion. Only downside of the LDO on this boaord is the drop-out-voltage which drops down at cirtain point depending on the current draw. Next version will get a bypass, when the dropout is reached it will automatically switch to the batery output.