arduino-lepton

FLIR Lepton drivers for Arduino HAL. Tested with ESP32-S3 + Lepton 3.5 on a custom board, but (in concept) should work on most Arduino platforms that have the enough memory and computational power.

Examples

All examples should build right out of the box with PlatformIO and have pinmaps defined at the top of main.cpp.

• ESP32-S3 webserver example with single-frame capture and streaming MJPEG, in greyscale or RGB888 (colorized) mode. Uses the JPEGENC library and FreeRTOS (part of all ESP32 builds). Likely compatible across the ESP32 family.

  

  Lightly refrigerated plush ducks over the webserver example, as viewed from a browser.

• Serial console example that prints frames to the console, each pixel being a single character (auto-scaled from 0-9). Likely works on any Arduino platform with a serial console, good basic test of functionality with minimal dependencies.

  

  Lightly refrigerated plush ducks over the serial console example.

Usage

FlirLepton lepton(i2c, spi, kPinLepCs, kPinLepRst);
uint8_t frameBuffer[160*120*2] = {0};

lepton.begin();  // resets the Lepton
while (!lepton.isReady());  // poll until Lepton reports ready

while (true) {
  bool readResult = lepton.readVoSpi(sizeof(frameBuffer), frameBuffer);  // returns true on a new frame
  if (readResult) {
    // do something with frameBuffer
  }
}

See full API in the header file.

Notes

• VoSPI is a timing-sensitive protocol and desynchronizes if frames are not read out promptly. If using an RTOS, the Lepton driver needs to be high priority to ensure SPI is running fast enough.
• In some cases (not quite sure why), the Lepton never returns any valid SPI data and constantly attempts to re-sync without success. Power-cycling / resetting the Lepton does not seem to fix the issue, though sometimes random modifications to the firmware might. Potentially related to using the VoSPI interface too early (?) or in-between frames (if not using the VSYNC signal).
• Only tested with Lepton 3.5, but likely works with all Lepton 3 devices (160x120 resolution). For other devices, you can try manually setting the video parameters with FlirLepton::setVideoParameters(uint8_t bytesPerPixel, uint8_t frameWidth, uint8_t frameHeight, size_t videoPacketDataLen, size_t packetsPerSegment, size_t segmentsPerFrame)
• readVoSpi blocks when reading a frame, but returns immediately during a discard frame. Future versions might look at splitting out the VoSPI into a different class that can have platform-specific optimized implementations, like using DMA and allowing other threads to run while a packet is being read.

Related Work

These projects do similar things:

• https://github.com/danjulio/tCam: ESP-IDF framework for ESP32E, GPL-3.0 license. Device firmware, not split into a library - though potentially could be done. Potentially needs companion apps to do anything.
• https://github.com/NachtRaveVL/Lepton-FLiR-Arduino: Arduino-based library, MIT license. Appears to be a dead project, last code update Aug 2020. Issues suggest potential issues with ESP32-S3 and Lepton 3.5.
• https://github.com/groupgets/purethermal1-firmware: STM32 using the STM32Cube (?) framework