Exercise 5: RFID Communication

Lesson Plan: RFID Communication and Signal Analysis

Lesson Objectives:

1. Understand how RFID systems work, including the principles of NFC (Near Field Communication).
2. Learn to interface an RFID module with Arduino to read and display tag data.
3. Use Red Pitaya to analyze I²C communication signals and capture the raw RF signals emitted by the RFID module.

Lesson Outline:

1. Introduction

• Topic Overview:
• RFID (Radio Frequency Identification) is a wireless technology used to identify and track objects using tags and readers.
• NFC is a subset of RFID operating at 13.56 MHz for short-range communication.
• Key concepts: I²C communication for data transfer, RF signal modulation, and tag detection.
• Why It Matters:
• RFID technology is widely used in access control, inventory management, and contactless payments. Understanding its operation and signal behavior is essential for designing reliable systems.

2. Hardware Setup

A. Components:

• Seeed Studio Grove NFC module v1.1:A versatile RFID/NFC module based on the PN532 chipset.
• Arduino Uno
• Red Pitaya STEMlab 125-14
• 4.7 kΩ Resistors: For I²C pull-up.

B. Circuit Assembly:

1. Connect the RFID Module:
• VCC to Arduino 5V.
• GND to Arduino GND.
• SDA to Arduino A4.
• SCL to Arduino A5.
• Add 4.7 kΩ pull-up resistors between SDA/SCL and 5V.
2. For Red Pitaya:
• Connect SDA and SCL to Red Pitaya IN1 and IN2 to monitor the I²C signals.
• Connect the RF antenna output (available on the module) to Red Pitaya for raw RF signal capture.

3. Arduino Programming: Reading RFID Tags

A. Basic RFID Tag Reading:

1. Install the required PN532 library (Adafruit PN532).
2. Write a sketch to read and display RFID tag data.
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#include <Wire.h>#include <Adafruit_PN532.h>#define SDA_PIN A4
#define SCL_PIN A5
Adafruit_PN532 nfc(SDA_PIN, SCL_PIN);

void setup() {
    Serial.begin(9600);
    nfc.begin();
    if (!nfc.init()) {
        Serial.println("Failed to detect NFC module");
        while (1);
    }
    Serial.println("Place an RFID tag near the module...");
}

void loop() {
    uint8_t uid[7];
    uint8_t uidLength;

    if (nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength)) {
        Serial.print("UID: ");
        for (uint8_t i = 0; i < uidLength; i++) {
            Serial.print(uid[i], HEX);
            Serial.print(" ");
        }
        Serial.println();
        delay(1000);
    }
}

3. Observe the UID of the RFID tag on the serial monitor.

4. Signal Analysis with Red Pitaya

A. I²C Communication Analysis:

1. Connect Red Pitaya’s IN1 to SDA and IN2 to SCL.
2. Open Red Pitaya’s oscilloscope tool and configure the channels for 0–5V.
3. Monitor the I²C signals:
• Check for noise, rise times, and signal integrity.
• Verify proper data transmission between Arduino and the RFID module.

B. RF Signal Capture:

1. Connect the RF antenna output to Red Pitaya IN1.
2. Use the oscilloscope to capture the raw 13.56 MHz RF signal emitted during RFID tag interactions.
3. Analyze the waveform:
• Observe how the signal changes when a tag is brought near the reader.
• Identify modulation patterns corresponding to data transmission.

5. Analysis and Insights

A. Understanding RFID Communication:

• Explain how the RFID reader and tag communicate using electromagnetic fields.
• Discuss how data is encoded and transmitted via I²C to the Arduino.

B. Signal Integrity:

• Highlight the importance of clean I²C signals for reliable communication.
• Discuss potential issues like noise, voltage mismatches, and their impact on RFID performance.

C. RF Signal Behavior:

• Analyze how the raw RF signal corresponds to data exchanges with the tag.
• Discuss factors like tag distance, orientation, and interference affecting signal quality.

6. Wrap-Up and Discussion

• Key Takeaways:
1. RFID systems rely on both digital and analog signals for operation.
2. Arduino provides basic interfacing and tag reading capabilities, while Red Pitaya enables advanced signal analysis.
3. Understanding I²C and RF signals helps optimize RFID systems for real-world applications.
• Real-World Applications:
• Contactless payments, asset tracking, and inventory management.

Homework/Extra Work

1. Experiment with different RFID tag orientations and distances to observe their impact on signal strength.
2. Use Red Pitaya to analyze the noise on I²C lines when introducing external interference (e.g., another electronic device nearby).