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.

Model: RFR101A1M


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.



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 :
   PIN1    TX
   PIN2    RX
   PIN4    GND
   PIN5    +5V(DC)
   PIN1    ANT1
   PIN2    ANT2
   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

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()


If you have questions or other better design ideas, you can go to our forum or wish to discuss.

Version Tracker

Revision Descriptions Release
v1.0 Initial public release Nov 03, 2008


How to buy

Click here to buy: http://www.seeedstudio.com/depot/125khz-rfid-module-uart-p-171.html?cPath=144_153. This product is off the shelf if you can not get to by the link. You can buy the high version Electronic brick - 125Khz RFID Card Reader at http://www.seeedstudio.com/depot/electronic-brick-125khz-rfid-card-reader-p-702.html?cPath=48_52.

See Also


This documentation is licensed under the Creative Commons Attribution-ShareAlike License 3.0 Source code and libraries are licensed under GPL/LGPL, see source code files for details.

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