RFID Reader Architecture - Raspberry Pi Bridge

Overview

This design describes how to connect a serial-only RFID reader (Shenzhen RFIDSU) to a Raspberry Pi, and expose two key interfaces for external clients:

• HTTP (REST API): Used to configure the reader (start/stop scanning, set parameters, etc.)
• WebSocket: Used to broadcast real-time tag reads to clients.

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Setup

python -m venv venv source venv/bin/activate # or venv\Scripts\activate on Windows pip install -r requirements.txt

System Diagram

+---------------------------------------+
|                 Client                |
| (Browser / Dashboard / Control App)   |
|                                       |
| 1. HTTP: Configure Reader (REST API)  |
| 2. WebSocket: Receive Tag Scans       |
+---------------------------------------+
                |
                |
      (Over Local Network or WiFi)
                |
+---------------------------------------+
|             Raspberry Pi              |
|                                       |
| +-------------------------------+    |
| | RFID Serial Reader Interface   |    |
| | - Reads EPC from serial port   |    |
| | - Handles reader commands      |    |
| +-------------------------------+    |
|               |                       |
| +-------------------------------+    |
| | HTTP Server (REST API)        |    |
| | - Set reader mode (scan/idle)  |    |
| | - Query reader status          |    |
| | - Configure parameters         |    |
| +-------------------------------+    |
|               |                       |
| +-------------------------------+    |
| | WebSocket Server              |    |
| | - Broadcasts tag reads        |    |
| | - Clients subscribe for live  |
| |   tag data                    |
| +-------------------------------+    |
+---------------------------------------+
                |
      (Connected via Serial)
                |
+---------------------------------------+
|        RFID Reader (Serial)           |
|  (Shenzhen RFIDSU, ISO18000-6C)       |
|                                       |
| Scans tags --> Sends EPC via Serial   |
| Receives config commands via Serial   |
+---------------------------------------+

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Summary of Roles

Component	Role
RFID Reader	Scans tags, sends tag data over serial, accepts configuration commands over serial
Raspberry Pi	Acts as a middleware — handles serial communication, provides configuration via HTTP, streams live tag data via WebSocket
Client App (Browser, Dashboard, etc.)	Configures the reader (via HTTP) and receives real-time tag data (via WebSocket)

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Protocols in Use

Protocol	Purpose
HTTP (REST)	Configure and control the reader (start/stop scanning, set power level, etc.)
WebSocket	Broadcasts live tag reads to connected clients
Serial (UART)	Direct communication between Pi and RFID reader

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Example Data Flow - Tag Scan

1. RFID reader scans a tag.
2. Reader sends EPC over serial to Raspberry Pi.
3. Raspberry Pi parses the serial message into structured JSON.
4. Pi broadcasts this JSON to all WebSocket clients.
5. Any connected client (dashboard, mobile app, etc.) instantly receives the tag event.

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Example Data Flow - Configuration

1. Client wants to start a scan session.
2. Client sends POST /api/start-scan to the Pi’s HTTP server.
3. Pi sends the corresponding serial command to the reader.
4. Reader begins scanning and sending tag data.
5. Tags appear on the client via WebSocket.

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Example Serial Data from Reader

(This part depends on the actual reader, but you might see something like:)

SOH <EPC_HEX> <TIMESTAMP> <CRC>

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Future Enhancements

• Add secure authentication to the HTTP and WebSocket interfaces.
• Add more advanced configuration options (scan intervals, power levels, antenna tuning).
• Optionally store tag scan events into a database for historical reporting.
• Add remote firmware update capabilities for the reader.

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End of Document