AERQ - Indoor air quality monitor

Introduction

This is the repository for AERQ, a USB-powered indoor air quality monitor using the here Bosch BME688 sensor, running on mbed os. It measures temperature, humidity, CO2 and IAQ using the BSEC 2.x library. This data is then sent to The Things Network.

PCB

This project features a custom 4 layer board using the Seeed E5-LoRa and the Bosch BME688. Two variants of the board, one with a chip antenna ( Linx USP-410 ) and one with a u.Fl connector.

Find more about the STM32WL - Seeed E5-LoRa.

For the PCB with the integrated antenna, click here here

For the PCB with an external u.Fl connector, click here

Code

The code runs on mbed os 6.15.1 with the latest LoRaWan stack. Insert your TTN credentials in mbed_app.json before running the application.

This code features a custom target on mbed os which configures the RF switch properly and adds a few macros for the board.

See mbed_app.json and custom_targets.json for more details.

Thanks to hallard for adding the support in the official mbed os custom target repository.

Payload decoder for TTN

The payload should provide the following result:

function Decoder(bytes, port) {
  // Decode plain text; for testing only 
  //var statusFromDevice = String.fromCharCode.apply(null, bytes.slice(12,13))
  
  let StringOfBytes = String.fromCharCode.apply(null, bytes);
  
  var temperature;
  var humidity;
  var iaq;
  var iaqAccuracy;
  var CO2;
  
  const Array = StringOfBytes.split(" ");
  temperature = Array[0];
  humidity = Array[1];
  statusFromDevice = Array[2];
  iaq = Array[3];
  CO2 = Array[4];
  
  var statusToDisplay;
  
  if (statusFromDevice == "0"){
      statusToDisplay = "Device warming up";
  } else if(statusFromDevice == "1")
  {
      statusToDisplay = "Device is adjusting to the envinroment - calibrating";
  }else if(statusFromDevice == "2")
  {
      statusToDisplay = "Environment has changed - re-calibrating";
  }
  else if(statusFromDevice == "2")
  {
      statusToDisplay = "Environment has changed - re-calibrating";
  }
  else if(statusFromDevice == "3")
  {
      statusToDisplay = "Device is calibrated and running";
  }
  else if(statusFromDevice == "4")
  {
      statusToDisplay = "Error communicating with the IAQ sensor. Critical";
  }
  
  
  return {
      Humidity: humidity,
      //IAQAccuracy:String.fromCharCode.apply(null, bytes.slice(12,13)),
      IAQ:iaq,
      CO2:CO2,
      Temperature:temperature,
      Status:statusToDisplay
  };
}

Android application

A simple KivyMD app was made for Android to receive packets:

Azure IoT Central

Data can also be parsed through Azure IoT Hub to the Azure IoT Central