The Atmel ATTiny 85 microcontroller will read the value of the sensor and send it to the main microcontroller via I²C. The main MCU can send this data to a server for example.
Firstly we will have to add the ATTiny to our Arduino IDE.
In the Arduino IDE, go to File -> Preferences and add the following url to Additional Boards Manager URLs and save with Ok.
https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json
To install the ATTiny board, got to Tools -> Board: and choose Board Manager Scroll down until you see attiny by David A. Mellis. Click on the Install button.
Now you will be able to see the ATtiny listed in the Board menu.
The following guide will explain how to program the ATtiny with another Arduino.
https://create.arduino.cc/projecthub/arjun/programming-attiny85-with-arduino-uno-afb829
If the ATTiny is still new there won't be any bootloader installed. We need a bootloader to be able to put our code on the ATTiny. Follow this guide to burn the bootloader to your ATTiny.
https://create.arduino.cc/projecthub/arjun/programming-attiny85-with-arduino-uno-afb829
You can find the program in the TinySalinity.ino file. The ATTiny will send its measurements over I²C on request.
In the ATtiny code is it possible to play with a few parameters. Change these to the preferred values.
// Default parameter values
#define I2C_SLAVE_ADDRESS 8
#define SAMPLE_COUNT 20
#define SAMPLE_TIME 7I2C_SLAVE_ADDRESS can be changed to any address between 8 and 119. Every slave device connected to the same master should have a unique address.
The moving average filter uses SAMPLE_COUNT and SAMPLE_TIME.
SAMPLE_COUNT describes how much readings have to be done before calculating the average of those readings.
SAMPLE_TIME is the time in milliseconds between every reading.