RFID Expansion for Micro:Bit
RFID Expansion for Micro:bit is an RFID device with an updated UART interface running at the frequency of 125KHz, Programmable Buzzer, two Dedicated slots for Servo Motor Interfacing, USB power port, and a compact design that compatibles with all the variants of Micro:bit, V1 and V2 both. It is developed with an expansion header to connect the RFID module with Micro:bit via easy stacking.
Features
 Standard RFID Expansion for Micro:bit 
 Two Dedicated slots for Servo Motor Interfacing 
 Programmable Buzzer
 Power and card LED indicator 
 Comes with development resources and material  
 USB power port to provide power to RFID module and Micro:bit 
Specifications
 Operating Voltage - 5V 
 Operating Frequency - 125 kHz 
 Communication Interface - External Pins ( GPIO and Power Pins)  
Default Baud Rate - 9600 bps 
 Dimensions - 55.82 x 68 mm 
 
  
 
Pinout
 | Expansion Pins  |  Micro:Bit Pins  | 
 |  RFID TX  |   P1  | 
 |  BUZZER  |   P8  | 
 |  SERVO 1  |   P2  | 
 |  SERVO 2  |   P16  | 
Programming
Drag and Drop
 Source code link : https://github.com/sbcshop/RFID-Expansion-For-Microbit/
 Attach Micro:bit on stackable connector of RFID Expansion of Microbit as shown below. 
Visit official programming website of Micro:Bit https://makecode.microbit.org/
Now Create a new project by clicking on "New project" tab and enter the name of your project.
Now drag and drop the block as shown in the image below and click on the download button to download it on your Microbit.
Tap RFID card, Keyfob, or Tag on RFID receiver to show 12 digits unique id of the card on the led matrix of Microbit.
Alternate Method
You can directly drag and drop test.hex file to Microbit to run the above said program and Tap card/Tag to display their unique id on led matrix.