Melexis MLX90614 IR sensor

Installing the sensor

How to install and commission the MLX90614 you can find in the datasheet. You can connect the sensor at the "I2C/NFC" connector on the FMU.

In the picture above the assembly of the sensor is shown. Solder the pre-assembled cable for the FMU connector with the sensor to a small breadboard and plug the other ends of the cables into the connector as shown. For better power stability, you can attach a capacitor between Vdd and ground.

The MLX90614 has an I2C and a PWM protocol. Per default the I2C protocol is activated. Switching between the modes is described in the datasheet on page 29.

Example code

Example code for using the MLX90614 under PX4 is available under the NXP HoverGames GitHub:

GitHub - NXPHoverGames/ThermoCam: Thermal Camera and Sensor for use with NXP HoverGames drone kit KIT-HGDRONEK66GitHub

The example was written in C++ and is based on the "px4_simple_app" in the examples folder of the PX4 Firmware. This example is in the folder "hg_mlx90614" and includes the files "CMakeLists.txt", "hg_temp.h" and "hg_temp.cpp".

For running the example the command hg_mlx90614 has to be added under the keyword "EXAMPLES" in the file "default.cmake" from the folder ".../src/Firmware/boards/nxp/fmuk66-v3" . Also copy the folder "hg_mlx90614" in the folder ".../src/Firmware/src/examples".

Within the example there are two public functions for reading the object temperature and the ambient temperature. These will be called as follows:

HG_Temp temp;
double objectTemp = 0;
double ambientTemp  =0;

objectTemp   = temp.readAmbientTempC();
ambientTemp  = temp.readObjectTempC();

First creating an object of the "HG_Temp"-Class. Then you can call the functions for reading the temperature. Both functions readAmbientTempC and readObjectTempC returns the temperature as a double type in degrees Celsius.