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125Khz RFID module - UART

RDM 125KHz card mini-module is designed for reading code from 125KHz card compatible read-only tags and read/write card . It can be applied in office/home security, personal identification, access control, anti-forgery, interactive toy and production control systems etc.

Note: Module will notify whenever 125khz tag approaches, tag serial number will be send via TX pin. Easy way for a RFID module on MCU projects or PC connnection via UartSB.


  • Support external antenna
  • Maximum effective distance up to 50mm
  • Less than 100ms decoding time
  • UART TTL interface
  • Support EM4100 compatible read only or read/write tags
  • Built-in external bi-color LED and buzzer driver
  • Small outline design


May include key specification and other specifications.

Key Specification​

Frequency 125KHz
Baud Rate 9600 (TTL Electricity Level RS232 format)
interface Weigang26 Or TTL Electricity Level RS232 format
Power supply DC 5V(±5%)
Current <50Ma
Operating range >50mm(Depend on Card/Tag shape, manufacturer)
Expand I/O port N/A
Indication light N/A
Working temperature -10℃~ +70℃
Storage temperature -20℃~ +80℃
Max. humidity Relative humidity 0 ~ 95%
Size 38.5mm ×19mm×9mm

Pin definition and Rating​

Look the image below(Mechanic Dimensions), and check the pin definition list here:

 Pin Definition : P1: PIN1    TX PIN2    RX PIN3 PIN4    GND PIN5    +5V(DC) P2: PIN1    ANT1 PIN2    ANT2 P3: PIN1    LED PIN2    +5V(DC) PIN3    GND

Mechanic Dimensions​


TTL Interface RS232 Data output format​

  1. 9600bps,N,8,1
  2. CHECKSUM: card 10byte DATA entire do XOR operation
    02 10ASCII Data Characters Chechsum 03

Example: card number: 62E3086CED

  • Output data:36H、32H、45H、33H、30H、38H、36H、43H、45H、44H
  • CHECKSUM: (62H) XOR (E3H) XOR (08H) XOR (6CH) XOR (EDH)=08H

Time sequence chart​


Output date(HEX): 02 | 30 31 30 30 30 37 33 34 45 30 | 44 32 | 03 ->Change to Decimal CardNumber Decimal: 48 49 48 48 48 55 51 52 69 48 CheckSum Decimal: 68 50 ->Refer to ASCII table,get Ascill value CardNumber Ascill: 0 1 0 0 0 7 3 4 E 0 CheckSum Ascill : D 2 (01H) xor (00H) xor (07H) xor (34H) xor (E0H) = D2H


Connect RX/TX to Arduino UART port , Uart demo code :

void setup()
void loop()


Tech Support​

if you have any technical issue. submit the issue into our forum.

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