Grand Idea Studio

RFID Read/Write Module


The Radio Frequency Identification (RFID) Read/Write Module provides a low-cost solution to read and write passive RFID transponder tags up to 4 inches away.

The RFID Read/Write module can be used in a wide variety of hobbyist and commercial applications, including access control, user identification, robotics navigation, inventory tracking, payment systems, car immobilization, and manufacturing automation.

The module works exclusively with the EM Microelectronic-Marin SA EM4x50 1kbit R/W transponder tags. Each tag contains a unique, read-only serial number (one of 232, or 4,294,967,296 possible combinations) and 116 bytes of user data area stored in a non-volatile EEPROM (Electrically Erasable Read Only Memory). The user data area can be optionally secured with a 32-bit password to allow only authorized read and write operations.

Parallax, Inc. is the exclusive manufacturer of the RFID Read/Write module. It is available in two versions: Serial (2-wire, 9600 baud, TTL-level) or USB. For questions and technical support, contact

Module Highlights:

  • Serial TTL or USB interface
  • Requires single +5VDC supply (USB version is bus-powered, no external supply needed)
  • 3.25″ L x 2.45″ W
  • Bi-color LED for visual indication of activity

Documentation (from Parallax):

Additional Resources (Serial Version):

Additional Resources (USB Version):



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