How To Use This NFC Reader Module

The ISO 14443 NFC reader project is built around an ESP32‑PICO‑D4 module and a TRF7970A NFC transceiver. The board implements a complete ISO 14443A reader, drives an output relay and provides connectors for indicator LEDs or other devices. When an ISO 14443A tag is brought near the antenna, the firmware reads its UID and toggles the relay. This allows you to trigger door locks, motors or other equipment when the correct NFC card is detected.

The following steps outline how to integrate and operate the NFC reader board. Understanding the power requirements, antenna tuning, relay connection and indicator usage is essential for a successful deployment.

• Power supply and inputs – Connect 10-24V input to the board’s supply pins. The internal LM5176 buck‑boost converter produces regulated 12V, and two regulators produce the 5V and 3V3 rails for the ESP32 and relay circuit. The relay can switch loads up to the rated current, and an optional PNP transistor allows control of a higher‑voltage load.
• NFC antenna and tag reading – The TRF7970A contains an analog front end and digital controller for ISO 14443A. It drives an external antenna through a matching network and communicates with the ESP32 over SPI. Adjust the antenna coil and tuning capacitors for resonance at 13.56 MHz, then upload firmware that reads the tag UID and drives the relay. When a compatible tag is presented, the firmware triggers the relay via a GPIO pin.
• Relay output – Connect the device you wish to control to the relay’s normally open (NO) and common (COM) terminals. The ESP32 toggles the relay when a valid tag is detected. You can modify the firmware to hold the relay closed for a fixed time or require multiple tag swipes.
• Indicators and peripherals – There are additional header pins for LEDs or other outputs. Use them to provide visual feedback when a tag is read or when the relay is active.

Unique Design Details

Beyond its basic functionality, this project teaches valuable lessons in component selection, power supply architecture, PCB layout and firmware design. The details below highlight these aspects in depth.

• Component choices – The TRF7970A supports multiple NFC protocols (ISO 14443A/B and FeliCa) and includes an RF field detector, modulator/demodulator and 1.8V digital interface. The ESP32‑PICO‑D4 integrates Wi‑Fi, Bluetooth and a microcontroller in a 7×7 mm package. Together these parts implement a compact wireless reader and controller.
• Power supply design – An LM5176 buck‑boost converter accepts a wide input range and produces a stable 12V rail. A secondary regulator supplies 3.3V for the ESP32 and TRF7970A. Following the reference designs and placing decoupling capacitors near every power pin minimizes noise on the NFC signal lines.
• PCB layout considerations – The board uses a four‑layer stack‑up with signal/ground/power/signal layers. A solid ground plane under the antenna and digital sections reduces EMI. Copper pour surrounding the antenna traces acts as a guard ring and helps isolate the RF section from the relay driver. Keep the antenna traces as short as possible and use a coplanar waveguide geometry to achieve a 50 Ω characteristic impedance.
• Firmware and expansion – The example firmware reads the UID of ISO 14443A tags and toggles the relay; however, you can expand it to support other ISO 14443 standards or implement password checking. The ESP32’s Wi‑Fi and Bluetooth radios can send tag data to a server or smartphone for logging. Because the design is open, engineers can customize the coil, relay circuit and firmware to suit access control or automation applications.

Engineers can modify the antenna, firmware and output stages to create customized NFC solutions for door locks, motor control or IoT devices.

The TRF7970A includes a configurable matching network and internal framing engine that supports other NFC standards beyond ISO 14443A. By selecting the appropriate modulation scheme and firmware routines, the board can communicate with cards conforming to ISO 14443B or FeliCa. Careful coil design and tuning capacitors maximize the magnetic field strength and reading distance. Additionally, the ESP32 supports sleep modes that can dramatically reduce power consumption when the reader is idle.

Additional Resources

Read the full guide article on Altium Resources for a deep dive on this project. The video below shows the design approach for the Rev A release of this project.