What Is Output of RFID Reader? Data Formats, Protocols, and Interfaces Explained

You hold a tag near a reader. A light flashes. Something happened. But what actually comes out of that reader? Is it just a number? Is it formatted for a database? Or is it raw radio signals that need decoding?

Here is the thing. When people search what is output of rfid reader, they usually discover that the answer depends on the reader type, how it is configured, and what system is listening on the other end. The output can be anything from raw binary data to neatly formatted strings ready for Excel.

Let me break down what RFID readers output, how they output it, and what it means for your application.

First: The Simple Answer

The output of an RFID reader is the data it extracts from tags plus metadata about the read event. At its most basic, this is the tag’s unique identifier—usually a number. But modern readers output much more: signal strength, antenna number, timestamp, and sometimes custom data from tag memory .

In a typical RFID system, the reader performs an inventory of tags in its field, collects data from each tag, and pushes that data somewhere for processing . Without that output, the reader is just a blinking box with no purpose.

What Data Actually Comes Out

When a reader successfully communicates with a tag, it can output several pieces of information :

Data Type	Description	Example
Tag ID / UID	The unique identifier of the tag	83 23 38 BB (hex)
EPC	Electronic Product Code (for UHF tags)	3008A2B4C6D8E0
TID	Tag Identifier (factory programmed)	E280110520007A
User memory	Custom data stored on the tag	PROD-12345
RSSI	Signal strength indicator	-65 dBm
Antenna number	Which antenna read the tag	Ant 1, Ant 2
Timestamp	When the read occurred	2026-03-17 14:23:15
Phase	Signal phase for direction sensing	142 degrees
Read count	How many times tag was seen	3

For hobbyist readers like the MFRC522 with Arduino, the output might be raw serial data showing the complete tag response, including checksums and protocol information . For example, an open source UHF reader might output binary arrays of RN16 and EPC data when it detects a tag .

Raw Output Formats

Different readers format their output differently. Here are common formats you might encounter:

ASCII text with delimiters: Many readers output tag data as ASCII strings with start and end characters. The Innovations ID-12 module, for example, outputs:

text

[STX][10 data bytes][2 checksum bytes][CR][LF][ETX]

The STX (start of text) is ASCII 02, data is 10 ASCII characters, followed by a 2-character checksum, carriage return, line feed, and ETX (end of text, ASCII 03) .

Binary data: Some readers, especially in industrial applications, output raw binary for efficiency. This requires software to interpret the bytes correctly.

Hexadecimal strings: The most common human-readable format. Tag UIDs are often displayed as hex bytes: 83 23 38 BB or 832338BB.

Decimal strings: Some access control systems expect tag numbers in decimal format. Readers can be configured to convert hex to decimal automatically.

JSON: Modern IoT-enabled readers output structured JSON data that is easy for web applications to parse .

Formatted Output for Applications

Raw tag data is rarely useful by itself. Most applications need the data formatted in specific ways. This is where reader configuration comes in .

Using tools like Zebra’s DataWedge, you can configure output formatting :

• Add prefixes and suffixes: Add colons, semicolons, or custom characters before and after each tag read
• Insert line breaks: Put each tag on a new line automatically
• Strip unwanted characters: Remove checksums or protocol data
• Convert formats: Change hex to decimal or vice versa
• Add separators between multiple tags: When reading many tags at once

For example, you might configure output to look like: TAG:832338BB; with each tag on its own line in a text file .

Physical Output Interfaces

The output has to travel from the reader to your system. RFID readers use various physical interfaces :

Serial interfaces:

• RS232: Traditional serial port, simple but limited distance (about 15 meters) 
• RS485: Differential signaling, longer distance (up to 1200 meters), supports multiple devices on same bus 
• TTL: 3.3V or 5V serial, common for embedded modules 

Network interfaces:

• Ethernet: 10/100 Mbps, TCP/IP output to network applications 
• Wi-Fi: Wireless network connectivity for mobile or difficult locations 
• PoE (Power over Ethernet): One cable for power and data 

USB interfaces:

• USB HID (keyboard emulation): Reader acts like a keyboard, types tag data into any application 
• USB CDC (serial): Creates a virtual COM port for traditional serial communication
• USB Mass Storage: Some readers can save tag data directly to a USB flash drive 

Specialized interfaces:

• Wiegand: Industry standard for access control readers, uses two data lines (D0 and D1) 
• GPIO: General purpose I/O for direct connection to relays, lights, or PLCs
• Bluetooth: Wireless for mobile applications 
• 4G/GPRS: Cellular connectivity for remote locations 

Output Protocols and Data Flow

Beyond the physical interface, the way data is packaged and sent matters :

Raw serial stream: Data is sent character by character as it is read. Simple but requires the receiving device to parse continuously.

TCP/IP sockets: Reader opens a network port (often 4001 or 5084) and streams tag data to connected clients. Can handle multiple connections.

HTTP POST: Reader sends tag data as HTTP requests to a web server. Good for cloud applications .

MQTT: Lightweight publish/subscribe protocol ideal for IoT applications. Reader publishes tag reads to topics that other devices subscribe to .

REST API: Modern readers have built-in web servers with REST endpoints for pulling tag data .

LLRP (Low Level Reader Protocol): Standard protocol for controlling readers and receiving tag data, used by many enterprise systems.

Middleware and Software Handling

Raw reader output often goes through middleware before reaching your application . Middleware can:

• Filter duplicate reads
• Aggregate data from multiple readers
• Format data for specific applications
• Store data temporarily if network is down
• Apply business rules (e.g., “if tag X is seen at antenna 2, trigger conveyor”)

Common middleware includes Impinj Speedway Connect, ThingMagic RAINstream, and Zebra FXConnect . These run on the reader itself or on a separate server.

Examples of Reader Output

Example 1: Simple USB reader in keyboard wedge mode

When you scan a card with a CYKEO CK-D1L in keyboard mode, the output going to your computer is exactly what you would see if you typed it:

text

0413277F9ED1

This 12-character string is the tag UID. It appears in whatever application has focus, just like keyboard input.

Example 2: Serial output from an open source UHF reader

When a tag is detected, the Arduino serial monitor might show :

text

RFID Reader V1.0
T1 (RN16) = 256.00 us
RN16[] = 1 1 0 1 1 1 1 0 0 0 0 0 0 1 1 1 
PC[] = 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 
L = 96
EPC[] = 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 1 1 1 0 1 1 0 0 1 0 ...
CRC[] = 0 1 0 0 0 0 1 0 1 1 1 0 0 1 1 1 
CRC 0K

This is raw protocol data, useful for debugging but not for applications.

Example 3: JSON output from modern IoT reader

A reader with REST API might output :

json

{
  "timestamp": "2026-03-17T14:23:15Z",
  "reader_id": "CYKEO-R8L-001234",
  "antenna": 1,
  "tags": [
    {
      "epc": "3008A2B4C6D8E0",
      "rssi": -65,
      "tid": "E280110520007A"
    },
    {
      "epc": "7F3C91A5B2D4F6",
      "rssi": -72,
      "tid": "E280110520008B"
    }
  ]
}

This is ready for direct use in web applications or databases.

Example 4: Wiegand output for access control

An access control reader sends pulses on two data lines . The pattern encodes the card number in a format that door controllers understand. You cannot see this output with a standard computer—it requires specialized hardware.

Choosing the Right Output for Your Application

Application	Recommended Output Type
Simple data entry into Excel	USB keyboard wedge
Access control system	Wiegand or RS485
Warehouse inventory with handhelds	Bluetooth + app
Fixed portal with conveyor	Ethernet + TCP/IP or MQTT
Embedded product development	TTL serial or module with SDK
Cloud-connected IoT system	HTTP POST or MQTT
PLC integration	RS485 with Modbus protocol

The Bottom Line

What is output of RFID reader? It is the data extracted from tags plus read metadata, packaged and transmitted through various interfaces for use by your applications.

The output can be:

• Raw data: Binary or ASCII straight from the tag
• Formatted strings: With delimiters, line breaks, and custom formatting
• Protocol-specific: Wiegand pulses, TCP streams, MQTT messages
• Visual: Lights and beeps for user feedback 

The right output for your project depends entirely on what you are trying to accomplish. A simple USB reader in keyboard mode is perfect for entering card numbers into a spreadsheet. A networked reader with JSON output is essential for cloud-based inventory systems.

CYKEO readers support multiple output formats and interfaces. Our CK-D1L desktop encoder works in keyboard wedge or serial mode. Our CK-B5L Bluetooth handheld rfid reader pairs with mobile apps. Our CK-R8L fixed reader offers Ethernet, RS485, and GPIO outputs with configurable data formatting.

When you are not sure what output you need, ask yourself: where does the data need to go? The answer will tell you everything.

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Need help matching reader output to your system?
CYKEO offers free integration consultations. Tell us about your application and we will recommend the right reader with the right output. Contact our team to get started.