SparkFun Qwiic RFID-IDXXLA Hookup Guide

Contributors: Elias The Sparkiest
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The Qwiic RFID ID-XXLA is an I2C solution that pairs with the ID-LA modules: ID-3LA, the ID-12LA, or the ID-20LA, and utilizes 125kHz RFID chips. Using the product's interrupt pin, we'll discuss how to get, store, and compare unique RFID IDs. Let's take a look at the hardware used for this RFID tutorial.

SparkFun RFID Qwiic Reader

SparkFun RFID Qwiic Reader

SparkFun RFID Qwiic Kit

SparkFun RFID Qwiic Kit


Required Materials

To follow along with this tutorial, you will need the following materials. You may not need everything though depending on what you have. Add it to your cart, read through the guide, and adjust the cart as necessary.

RFID Reader ID-12LA (125 kHz)

RFID Reader ID-12LA (125 kHz)

SparkFun RedBoard Qwiic

SparkFun RedBoard Qwiic

USB micro-B Cable - 6 Foot

USB micro-B Cable - 6 Foot

Jumper Wires Premium 6" M/M Pack of 10

Jumper Wires Premium 6" M/M Pack of 10

Qwiic Cable - 50mm

Qwiic Cable - 50mm

RFID Tag (125kHz)

RFID Tag (125kHz)



You will need a soldering iron, solder, and general soldering accessories.

Soldering Iron - 30W (US, 110V)

Soldering Iron - 30W (US, 110V)

Solder Lead Free - 15-gram Tube

Solder Lead Free - 15-gram Tube


Suggested Reading

If you aren't familiar with the Qwiic system, we recommend reading here for an overview.

Qwiic Connect System
Qwiic Connect System

We would also recommend taking a look at the following tutorials if you aren't familiar with them.


An introduction to I2C, one of the main embedded communications protocols in use today.

RFID Basics

An overview of Radio Frequency Identification (RFID) technology.

Hardware Overview

Qwiic Connectors

This is a Qwiic product but not a "pure" Qwiic product. You'll still need to solder or connect the interrupt pin if you decide to use that to indicate when an RFID card has been read (more on that later). Outside of that, Qwiic is an eco-system designed for I2C devices that allows you to prototype quickly without needing to solder anything. Just plug your Qwiic product into a Qwiic capable microcontroller and you're good to go! There are two on this product which means you can daisy chain the product with other I2C devices, like a Qwiic Keypad for example.

The two large connectors on the product are the Qwiic connectors and are highlighted in this picture.


The SparkFun Qwiic RFID ID-xxLA is a 3.3V system. You can power the product with a Qwiic cable plugged into a capable microcontroller. You can also provide power through the 3V3 pin on the header.

LEDs and Buzzer

When you provide power to the board you will see the onboard red power LED light up. There's another LED opposite the power LED labeled READ. This blue stat LED and the onboard buzzer will light or beep respectively when an RFID tag is brought into range.

The image shows the ATtiny side of the product with the power and read LEDs above the connectors highlighted. The image shows the buzzer on the side of the RFID reader

RFID Modules

There are three ID-xxLA options in our catalog that are listed above in the Introduction: the ID-3LA, the ID-12LA, and ID-20LA. If you purchased the SparkFun RFID kit then it includes the ID-12LA and RFID cards that you need. Pictured below is the ID-12LA plugged into the Qwiic RFID.

Pictured is the product with the RFID module plugged into its headers.

Each option is similar but there is a small variance in power consumption which translates into different read range capabilities. The ID-3LA is designed to be used with an external antenna which will get you 30cm of range. The ID-12LA and ID-20LA have a range of 12cm and 18cm respectively.

When plugging in your module, just take care that the side with less pins goes into the header with less pins.

Pictured is the module with the two female headers highlighted.

Smaller header on the left, larger on the right.


There are four jumpers on the header side of the product. Facing the product with the buzzer at the top, you'll see a jumper on the left side labeled INT. The interrupt pin can be disconnected here by cutting the trace. Now moving to the bottom near the header is a jumper labeled I2C that connects the I2C pull-up resistors to the I2C data lines. On the right side is a jumper labeled Buzzer that disconnects the buzzer when cut. This will disable the beeping sound when a RFID card is in range. Finally, the ADDR jumper allows you to change the default I2C jumper from 0x7D to 0x7C.

There are four jumpers on the side of the header side of the product that are highlighted in this picture.

Hardware Assembly

Simply insert a Qwiic cable between the RedBoard Qwiic and the Qwiic RFID reader. You will also need to solder wire between the Qwiic RedBoard's pin 8 and the Qwiic RFID reader's INT pin. When you are ready, align the headers of the module with the Qwiic RFID reader.

Here is an image of the Qwiic RFID module connected to the Redboard Edge via a Qwiic cable with an additional wire connecting the product's interrupt with pin 8 on the Redboard.

Note: The Qwiic system has a logic level of 3.3V. I have attached the interrupt to pin 8 on the Redboard Qwiic even though the pin is at 5 volts. This will not harm the Qwiic RFID because we're doing a simple digitalRead() but also because the ATTiny84 is tolerant of voltages up to 5.5V.

Example Code

Note: This example assumes you are using the latest version of the Arduino IDE on your desktop. If this is your first time using Arduino, please review our tutorial on installing the Arduino IDE.

Let's take a look at the first example code for the SparkFun Qwiic RFID ID-xxLA. You can download all the example code from the GitHub Repo or by clicking the link below.

Example 1 - Read Tag

For the scope of the tutorial, let's start at the top of Example1_ReadTag.ino. Open the example located in the in the examples folder: SparkFun_Qwiic_RFID_ID-XXLA > Firmware > Arduino_Examples > Example1_ReadTag . We use Arduino's I2C library called Wire. The product's default address is at 0x7D but can be changed to 0x7C by closing the ADDR jumper. You will also need to adjust the code to reference the RFID_ADD. TAG_REQUEST is the size of the RFID tag that we'll request from the Qwiic RFID when the interrupt pin attached to pin 8 goes low.

#include <Wire.h> 

#define RFID_ADDR 0x7D // Default I2C address 
//#define RFID_ADD 0x7C // Close "ADDR" jumper for this address
#define TAG_REQUEST 6

// We'll use a pin attached to the interrupt line to initiate the check for the RFID tag ID. 
// Alternately the product can store up to 20 tags. 
const int eventPin = 8;  

void setup()
    // Begin I-squared-C
    Serial.println("SparkFun Qwiic RFID, waiting for RFID to be scanned."); 
    pinMode(eventPin, INPUT_PULLUP);// Our pin is active low so let's put it in a known high state.

In the loop, we're just monitoring the Qwiic RFID's interrupt pin that will indicate that a tag has just been read. Alternately, we could skip this and read it after an arbitrary amount of time to see the different tags that were scanned over some period of time. If you go this route, keep in mind that only 20 tags are stored at a time on the product.

When we read an interrupt, there is a call to the function checkTagID() that checks to see what tag has been read.

void loop()
    // When the interrupt pin changes to a LOW state, a tag has been scanned. 
    if( digitalRead(eventPin) == LOW ) checkTagID();
    delay(250); // Slow it down

This is the meat of the code. It's a simple request to the product to hand over the first RFID tag that was scanned. Keep in mind that the product gives tags in the order that they are scanned. Each scan is unique because each tag that is scanned, gets a time stamp attached to it.

// 20 tags can be stored by the product at a time, the first one to be scanned is the first one
// to be pulled from the tag stack. If the tag reads '000000' or the interrupt line never went low
// then there are no new tags waiting to be read. 
void checkTagID()
  byte tempTag = 0; 
  // This variable stores the tag and could easily be a global variable. Just
  // make sure to clear it in between reads. 
  String tagID; 
    Serial.print("RFID Tag ID: "); 
    Wire.requestFrom((uint8_t)RFID_ADDR, TAG_REQUEST); 
    for( int x = 0; x < TAG_REQUEST; x++ ) {
    tempTag =; 
    // Concatenating the bytes onto the end of "tagID".
    tagID += String(tempTag); 

If you have not already, select the board and COM port of your Arduino and upload the Example1_ReadTag.ino code. Then open your Serial Monitor at 9600 and scan a tag,

There is a gif here showing a person placing their RFID tag in range of the RFID module.

You should see the following:

Pictured is an image of Arduino's Serial Monitor with an RFID tag's number printed.

Resources and Going Further

Now that you've successfully got your Qwiic RFID Reader up and running, it's time to incorporate it into your own project!

For more information, check out the resources below:

We carry other RFID options. Do you want a high powered RFID reader that can simultaneously pick up multiple RFID cards at a time? Perhaps you'd rather a RFID card reader that transmits over serial, check out the options below.

SparkFun Simultaneous RFID Reader - M6E Nano

SparkFun Simultaneous RFID Reader - M6E Nano

SparkFun RFID Starter Kit

SparkFun RFID Starter Kit


Need some inspiration for your next project? Check out some of these related tutorials tagged with RFID:

SparkFun RFID Starter Kit Hookup Guide

Learn the basics of how to get started with the SparkFun RFID Starter Kit.

Simultaneous RFID Tag Reader Hookup Guide

A basic guide to getting started with the RFID Tag Reader breakout and how to read and write multiple RFID tags over multiple feet!

RFID Basics

An overview of Radio Frequency Identification (RFID) technology.

Build a Qwiic Jukebox that is Toddler Approved!

Follow this tutorial to build your own custom jukebox. Note, this is designed simple and tough for use primarily with toddlers. It's also a great introduction to SparkFun's Qwiic products!

Or check out this blog post for ideas: