Hello everyone. I welcome you to my one to last blog post as part of Experimenting with Gesture Sensors. In previous blog post I shown my final project. Today I will show one of my experiments which I have done as part of experimenting with the sensor. Today I will show how two MAX25405 sensor works.

If you remember my blog Blog #8: 12V Accident, I burned my kit, ordered new kit, but later I decided to fix broken kit, so now I have two kits (fixed burned kit and new kit). This allows me to try sensor synchronization features of the MAX25405 sensor when using two sensors at the same time. The issue is that when using two sensors, their infra-red LEDs interfere with LEDs form other kit.

Improving stand for allowing using two sensors

For my initial experiments with this setup, I upgraded my stand which I originally developed for using with single sensor and described in previous Blog #4: Building stand for MAX25405 EVKIT. Now it allows me to mount two sensors very near each other. Stands from, building set is much more flexible than plastic 3D printer stands as you can see. This is not practical setup for using two sensors. It does not make sense to place two sensors in the very similar position. Instead with two sensor practical use case is to set sensors at different positions allowing them sensing gestures from two points of view which can later allow more precise and accurate gesture detection. But this setup was done mainly for experimenting with sensor and allows me for example compare sensor outputs as you will see later.

Connecting Two Sensors

MAX25405 allows two interface and in both cases, it allows running two sensors by the same master. In case of I2C bus it is achieved by two I2C addresses and in case of SPI it can be achieved by using two chip select ports. In my experiments I used SPI bus, so I was driving and selecting sensor by CS pins. My library has support for this feature for both buses. As a microcontroller I used MAX78000 on FTHR board the same as in previous project. For an application I configured sensor, implemented support for receiving interrupt from both sensors and after they interrupted I read new screen data. These I printed over UART. For visualization I used WebSerial API. I edited it to support output format from my MCU application and also added second table for visualizing data from second sensor.