Of course you need to make the connection removable so you can (re-) flash the ESP as needed.
As I understand, this board outputs Wiegand (so not only the serial of the fob in plain format) in the following format:
- Data Head = 0x02 (fixed byte)
- Length = 0x0A (total length of the packet is 10 bytes for 125kHz fobs)
- Card Type = 0x02 (EM4100 = 125kHz chips)
- Card Serial = SN0~SN4 (5 bytes)
- BCC Check = XOR Check (Except Data Head And Data End)
- Data End = 0x03 (fixed byte)