ESP8266 Community Forum

Good morning Today I received the "rfid 7941E v.3" reading module from aliexpress. The reader reads em4100 tag at 125khz. I do not have much experience and I would like to ask you some connection ideas with arduino or esp8266. Can you help me? thank you

I'm not sure about this one (I've got different boards), but if it also is just emitting the RFID keyfob numbers in a RS-232 formatted serial way, you can just connect it to the RX (GPIO3) of the ESP (don't forget to include a level-shifter if needed) and read the data as is.

Of course you need to make the connection removable so you can (re-) flash the ESP as needed.

[EDIT]
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)