FLIR Lepton Integration Guide: Hardware, Software, and Raspberry Pi Setup

Introduction

Note: This guide was originally written for the FLIR Lepton KIT‑13233, but the FLIR Lepton 2.5 with Radiometry works the same.

When our team began testing a Long‑Wave Infrared (LWIR) camera, we were instantly excited by the prospect of “seeing the invisible.” Whether we’re monitoring a remote jungle or simply preventing a hot mug from scalding us, the FLIR Lepton offers a compact, affordable gateway into thermal imaging.

FLIR Lepton is an excellent module for its price, and Pure Engineering’s breakout board and documentation make it straightforward to integrate.

FLIR Radiometric Lepton Dev Kit

FLiR Dev Kit

While the setup is simple, there are a few nuances worth noting. Below we share the insights we gained and provide a step‑by‑step walkthrough.

Required Materials

To follow this tutorial you’ll need a handful of hardware and software components. Depending on your existing setup, you may not need everything listed below. Add items to your cart, review the guide, and adjust as necessary.

Hardware

We’ll be using the Raspberry Pi example code supplied by Pure Engineering and featured in their product videos. At a minimum, you’ll need:

• A Raspberry Pi (any model running Raspbian)
• Flir Lepton camera module (any version)
• Jumper wires (F/F) – 20 AWG preferred
• Monitor, keyboard, and power supply for the Pi
• Optional: 7″ touchscreen or SmartiPi Touch for a more integrated display

Below is a suggested parts list. Feel free to skip items you already have.

FLIR Lepton Hookup Guide Wishlist – SparkFun Wish List

Raspberry Pi LCD – 7″ Touchscreen

SmartiPi Touch

Multimedia Wireless Keyboard

Raspberry Pi 3 B+ Starter Kit

FLIR Radiometric Lepton Dev Kit

Tip: For a minimal setup you can wire the Lepton directly to the Pi with solid‑core 22 AWG wires. For a more robust connection, consider soldering a custom Raspberry Pi HAT.

Hook‑Up Wire – Assortment (Solid Core, 22 AWG)

Jumper Wires Premium 6″ F/F – 20 AWG (10 Pack)

SparkFun Snappable Protoboard

Raspberry Pi GPIO Tall Header – 2×20

If you purchase the PureThermal 2 – FLIR Lepton Smart I/O Board, note that it does not include the Lepton camera module. However, it provides USB‑based control and raw video data, which is ideal for using the camera as a USB webcam.

PureThermal 2 – FLIR Lepton Smart I/O Board

USB micro‑B Cable – 6 Foot

For detailed instructions on setting up the Smart I/O board with your computer, see the following videos:

• Windows
• Mac OS
• Raspberry Pi

Software

The example code has been tested on a Raspberry Pi Model B, but it will run on any Pi model with Raspbian installed.

RASPBIAN IMAGE

In addition, you’ll need the Qt development tools and the Pure Engineering example code. See the Software section below for step‑by‑step instructions.

Theory

The electromagnetic spectrum spans from high‑energy gamma rays to low‑frequency radio waves. Most consumer cameras capture visible light (380–700 nm). Long‑wave infrared (LWIR) sensors, like the Lepton, detect radiation in the 9–14 µm range—exactly the wavelengths emitted by objects near room temperature.

Electromagnetic spectrum with visible light highlighted. Image courtesy of Wikimedia Commons.

The Lepton’s core is a microbolometer array. Microbolometers change electrical resistance in response to absorbed infrared energy. By measuring this resistance, the sensor calculates surface temperature and produces a false‑color image that encodes temperature data.

Thermal imaging finds applications in building diagnostics, automotive cooling analysis, medical diagnostics, and night‑vision systems. In robotics, thermal cameras enable heat‑centroid detection using standard image‑processing libraries such as OpenCV—making heat‑seeking robots a realistic DIY project.

Hardware Overview

Below are key specifications for the two most common Lepton variants. Cells highlighted in blue indicate differences between the original Lepton and the Lepton 2.5 with Radiometry.

	FLIR Lepton	FLIR Lepton v2.5 w/ Radiometry
Resolution	80 × 60 px	80 × 60 px
Spectral Range	8–14 µm	8–14 µm
Horizontal Field of View	51°	50°
Thermal Sensitivity	<50 mK	<50 mK
Frame Rate	<9 Hz	<9 Hz
Control Interface	I²C	I²C
Video Interface	SPI	SPI
Time to Image	<0.5 s	<1.2 s (≈0.5 s in real‑world testing)
Integral Shutter	✓	✓
Radiometry	14‑bit pixel value	14‑bit pixel value, Kelvin
Operating Power	≈150 mW	≈150 mW

Hardware Hookup

⚠️ Warning: Although the Lepton module is tolerant of electrostatic discharge, it is a precision component. Handle with care and avoid static‑charged surfaces.

Circuit Diagram

Connect the Lepton breakout board to the Raspberry Pi GPIO pins following the diagram below. If you need a refresher on GPIO pinout, refer to our Raspberry Pi GPIO tutorial. Ensure the Lepton module is securely snapped into the breakout socket.

Typical setups using a breadboard and touchscreen are illustrated in the images below.

Congratulations—you’ve completed the hardware assembly. Next, we’ll configure the software.

Software

Begin by installing Raspbian on your Raspberry Pi. Once booted, open a terminal and enable the Pi’s SPI and I²C interfaces via the raspi-config utility:

sudo raspi-config

Navigate to Advanced Options → SPI, then repeat the process for I²C. After each selection, reboot the Pi to apply the changes.

The Pure Engineering example is a Qt application, so install the Qt development tools:

sudo apt-get install qt4-dev-tools

Next, download the example code from the Pure Engineering GitHub repository. You can clone the repository or download the ZIP archive and unzip it. Then navigate to the raspberrypi_video directory:

cd LeptonModule-master/raspberrypi_video

Compile the Lepton SDK first:

cd ../software/raspberrypi_libs/LeptonSDKEmb32PUB
make

Return to the raspberrypi_video directory and build the application:

qmake && make

Once the build completes, launch the application with:

./LeptonVideo

You should now see a live thermal feed from your Lepton camera. From here, you can experiment with OpenCV, data logging, or integrate the camera into a robotics project.

Additional Resources

• Pure Engineering Lepton SDK Documentation
• OpenCV Thermal Image Processing Tutorial

Thank you for following the FLIR Lepton Hookup Guide. Happy imaging!