ESP8266 Community Forum

- Thu Aug 30, 2018 6:48 am #78025 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

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- Mon Sep 03, 2018 4:16 am #78073 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)

Assumption is the mother of all f*ckups. At least: that's what I'm assuming.