Fast (23 fps) MLX90640 based Thermal Camera for Raspberry Pi Pico (RP2040)

A simple but fast Thermal Imaging Camera using the MLX90640 sensor, a 1.5 inch RGB OLED Display Module, and two optional touch sensor modules.

Features

• fast: 23 frames per second by employing both cores of the RP2040 (whereas a single core would only result in 11 fps):
  • core0 fetches the pages from the MLX90640 and scales the data down to 8-bit integers
  • core1 renders the data on the OLED after optionally smoothing the data by bilinear interpolation
  • using an RP2350 results in 28 fps
• configurable heat-map (predefined 7-colors, 5-colors, 2-colors, and grey map)
• touch button for disabling interpolation
• touch button for freezing the displayed image

Code Based on

• unmodified Melexis Driver: https://github.com/melexis/mlx90640-library/
• heat map code inspired by: http://www.andrewnoske.com/wiki/Code_-_heatmaps_and_color_gradients
• the Pico SDK

Hardware

• Raspberry Pi Pico (RP2040) or Pico 2 (RP2350)
• MLX90640 Thermal Camera Breakout (55º or 110º), e.g. Pimoroni
• 1.5inch RGB OLED Display Module, 65K RGB Colors, 128×128, SPI, e.g. Waveshare
• Optional: 2 buttons, e.g. TTP223 Touch Sensor Modules
• Optional: battery module, e.g. LiPo Charger/Booster module

Wiring

Connect the MLX90640 and the OLED to the 3.3 V Pin 36 of the Raspberry PI Pico.

MLX90640	RP2040	GPIO	Pin
SDA	I2C0 SDA	16	21
SDC	I2C0 SDC	17	22

OLED	RP2040	GPIO	Pin
DC	SPI1 DC	9	12
CLK	SPI1 SCK	10	14
DIN	SPI1 TX	11	15
CS	SPI1 CSn	13	17
RST	RST	15	20

Touch Buttons	GPIO	Pin
Disable Interpolation	14	19
Freeze Image	18	24

Building

• make sure the "Pico SDK" is installed and the environment variable "PICO_SDK_PATH" refers to it.
• git clone https://github.com/weinand/thermal-imaging-camera
• cd thermal-imaging-camera
• git submodule init
• git submodule update
• mkdir build
• cd build
• cmake -DPICO_BOARD=pico ..
• make thermocam

To build for Pico 2 (with the faster rp2350) delete the build directory and then use these steps:

• mkdir build
• cd build
• cmake -DPICO_BOARD=pico2
• make thermocam

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