CLRC663 NFC RFID Reader Module Documentation

CLRC663 Documentation covers quick start steps, SPI/I2C/UART interface selection, ESP32 and Arduino wiring, LPCD low-power mode, and troubleshooting for the ELECHOUSE CLRC663 Reader Module V1.

Quick Start

  1. Select the interface via the on-board DIP switch: SPI, I2C, or UART. No soldering required.
  2. Wire the module to your host MCU using the selected interface pins.
  3. Power the module with 5V (RF supply) and ensure the logic/IO pins are connected to your host.
  4. Install the ELECHOUSE CLRC663 Arduino library from GitHub.
  5. Open a basic card-detection example, compile, upload, and tap a tag.

Key Technical Facts

Parameter Value
Chip NXP CLRC66303
Operating frequency 13.56 MHz
RF supply (Pin 1) 4.5V – 5.5V (5.0V recommended for maximum range)
Logic / IO voltage (Pin 8) 3.3V – 5.5V
Interfaces SPI, I2C, UART (DIP switch selection)
Typical read range Up to 9 cm (Mifare Classic, 5V RF)
LPCD Hardware low-power card detection
SAM interface Dedicated I2C port for NXP SAM AV2/AV3

Interface Selection (DIP Switch)

The ELECHOUSE CLRC663 module selects the active interface via an on-board DIP switch. Refer to the PCB silkscreen for switch positions.

Interface DIP Switch Position Best For
SPI See silkscreen Fast, reliable, most Arduino/ESP32 examples
I2C See silkscreen Fewer wires, shared bus
UART See silkscreen Simple serial communication

Important: Set the DIP switch before powering the module. Do not change the interface while powered.

ESP32 Wiring (SPI)

CLRC663 Pin ESP32 Notes
5V (RF) VIN or external 5V RF antenna supply — must be 5V for max range
3V3 (Logic) 3.3V IO logic supply
GND GND Common ground
MOSI GPIO23 SPI MOSI
MISO GPIO19 SPI MISO
SCK GPIO18 SPI clock
CS / NSS GPIO5 SPI chip select
IRQ GPIO4 Interrupt (optional)

Arduino Uno Wiring (SPI)

CLRC663 Pin Arduino Uno Notes
5V (RF) 5V RF supply
3V3 (Logic) 3.3V Logic supply
GND GND Common ground
MOSI D11 SPI MOSI
MISO D12 SPI MISO
SCK D13 SPI clock
CS / NSS D10 SPI chip select

Supported Protocols

Protocol Standard Typical Tags Support
ISO 14443A ISO 14443A Mifare Classic, Ultralight, NTAG, DESFire ✓
ISO 14443B ISO 14443B Bank cards, national ID chips ✓
ISO 15693 ISO 15693 ICODE SLI, ICODE SLIX2, industrial vicinity tags ✓
FeliCa ISO 18092 Suica, Octopus, PASMO ✓
Card emulation — — ✗ Reader/Writer only

Example Code (SPI, ESP32)

#include <SPI.h>
#include "CLRC663.h"  // ELECHOUSE CLRC663 library

#define CS_PIN  5
#define IRQ_PIN 4

CLRC663 rfid(CS_PIN, IRQ_PIN);

void setup() {
  Serial.begin(115200);
  SPI.begin();
  rfid.begin();
  rfid.softReset();
  Serial.println("CLRC663 ready");
}

void loop() {
  uint8_t uid[10];
  uint8_t uidLength = rfid.readPassiveTargetID(uid);
  if (uidLength > 0) {
    Serial.print("Tag UID: ");
    for (int i = 0; i < uidLength; i++) {
      Serial.printf("%02X ", uid[i]);
    }
    Serial.println();
    delay(1000);
  }
}

Refer to the ELECHOUSE GitHub repository for full library installation instructions and additional examples (ISO 15693 inventory, LPCD wake-on-card).

LPCD (Low Power Card Detection)

The CLRC663 supports hardware LPCD, allowing battery-powered devices to sleep and wake only when a card is presented. This is ideal for:

  • Smart locks and door access that must run on battery for months
  • Portable NFC readers with long standby time
  • Industrial readers powered by energy harvesting

In LPCD mode, the CLRC663 briefly activates the RF field at a configurable interval, checks for a card, and sends an interrupt signal to the host if detected. Average current draw in LPCD mode can be under 1 mA depending on poll interval.

CLRC663 vs PN532 — When to Choose Each

CLRC663 PN532
ISO 15693 ✓ ✗
Typical read range Up to 9 cm 5–8 cm
LPCD ✓ Hardware Limited
Card emulation ✗ ✓
Interface options SPI / I2C / UART (DIP switch) SPI / I2C / UART (solder jumper)
Arduino library ecosystem Smaller Large
SAM support ✓ Dedicated I2C port ✗

Troubleshooting

  • No response from module: Verify DIP switch matches your wiring mode. Confirm 5V RF supply and 3.3V logic supply are both connected.
  • Short read range: Ensure RF supply is 5.0V. At 3.3V RF supply, range is significantly reduced.
  • Cannot read ISO 15693 tags: Confirm DIP switch is set to the selected interface and library supports ISO 15693 mode. Use the ISO 15693 inventory example sketch.
  • SPI conflicts: If sharing the SPI bus with other devices, ensure CS lines are properly controlled.

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