(C) Copyright, 2026 G. Schaer.

This work is licensed under a GNU General Public License 3.0.

SPDX-License-Identifier: GPL-3.0-only

Lepton3.5_Purethermal3

Software to run a FLIR Lepton 3.5 mounted on a Groupgets Purethermal3 board running in Windows.

Installation

From PyPi (Recommended)

It is recommended that you use either Anaconda or Miniconda.

Run the commands below to create a fresh conda environment named lepton.

conda create -n lepton -y
conda activate lepton

Install pip in the environment.

conda install pip -y

Install lepton-pt

pip install lepton-pt

From Source

It is reccomended that you use either Anaconda or Miniconda.

Run the commands below to create a fresh conda environment named lepton.

conda create -n lepton -y
conda activate lepton

Install pip and git in the environment.

conda install pip git -y

Clone the Lepton3.5_Purethermal3 repository.

git clone https://github.com/GrayKS3248/Lepton3.5_Purethermal3.git

Navigate to the repository directory and install the package.

cd Lepton3.5_Purethermal3
pip install -e .

Usage

Streaming

After the Lepton is seated in the Purethermal board and connected to a device via a USB-C, activate the Conda environment in which this package is installed and start streaming the camera using the leprun command.

conda activate lepton
leprun

When you are finshed streaming, press the esc while the viewer window is active to terminate the streaming.

Recording

After the Lepton is seated in the Purethermal board and connected to a device via a USB-C, activate the Conda environment in which this package is installed and start streaming the camera using the leprun command and the -r flag.

conda activate lepton
leprun -r

The -r flag indicates that you want to record what is being streamed. All generated data is saved in a subdirectory of the directory Lepton_Recordings. Lepton_Recordings is found in the active directory. After the recording is terminated, data is rendered into a .mp4 video.

When you are finshed recording, press the esc while the viewing window is active to terminate recording. Note that it will take some time after the recording is terminated to render the captured video.

Other

You can use the -h flag to explore addtional flags and functionality.

leprun -h

Coding Examples

Example usage is given in the examples directory.

Lost Frames Every 3 Minutes

The FLIR Lepton camera uses automatic flat field correction (FFC) during operation to ensure image fidelity and prevent pixel drift. These automatic FFCs occur every 3 minutes and are predicated by a box reading "FFC" in the top left corner of the viewing window. They last approximately 2 seconds during which no thermal or telemetry data are transmitted by the camera resulting in dropped frames. This is unavoidable for proper Lepton function. Note the renderer automatically detects the dropped frames and locally adjusts the frame rate to maintain true playback speed.