arduino/examples/TVOC/TVOC.ino

/*
This is the code for the AirGradient DIY Air Quality Sensor with an ESP8266 Microcontroller.

It is a high quality sensor showing PM2.5, CO2, Temperature and Humidity on a small display and can send data over Wifi.

For build instructions please visit https://www.airgradient.com/diy/

Instructions on using the TVOC sensor (SGP30) instead of the Temperature / Humidity sensor (SHT3x).

https://www.airgradient.com/resources/tvoc-on-airgradient-diy-sensor/

The codes needs the following libraries installed:
"WifiManager by tzapu, tablatronix" tested with Version 2.0.3-alpha
"ESP8266 and ESP32 OLED driver for SSD1306 displays by ThingPulse, Fabrice Weinberg" tested with Version 4.1.0
"SGP30" by Rob Tillaart tested with Version 0.1.4

Configuration:
Please set in the code below which sensor you are using and if you want to connect it to WiFi.

If you have any questions please visit our forum at https://forum.airgradient.com/

If you are a school or university contact us for a free trial on the AirGradient platform.
https://www.airgradient.com/schools/

MIT License
*/

#include "SGP30.h"
SGP30 SGP;

#include <AirGradient.h>
#include <WiFiManager.h>
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>

#include <Wire.h>
#include "SSD1306Wire.h"

AirGradient ag = AirGradient();

SSD1306Wire display(0x3c, SDA, SCL);

WiFiClient client;

// set sensors that you do not use to false
boolean hasPM=true;
boolean hasCO2=true;
boolean hasSHT=false;
boolean hasTVOC=true;

// set to true if you want to connect to wifi. The display will show values only when the sensor has wifi connection
boolean connectWIFI=true;

// change if you want to send the data to another server
String APIROOT = "http://hw.airgradient.com/";

void setup(){
  Serial.begin(9600);

  display.init();
  display.flipScreenVertically();
  showTextRectangle("Init", String(ESP.getChipId(),HEX),true);

  if (hasTVOC) SGP.begin();
  if (hasPM) ag.PMS_Init();
  if (hasCO2) ag.CO2_Init();
  if (hasSHT) ag.TMP_RH_Init(0x44);

  if (connectWIFI) connectToWifi();
  delay(2000);
}

void loop(){

  if (hasTVOC) SGP.measure(false);

    // create payload

  String payload = "{\"wifi\":" + String(WiFi.RSSI()) + ",";

  if (hasPM) {
    int PM2 = ag.getPM2_Raw();
    payload=payload+"\"pm02\":" + String(PM2);
    showTextRectangle("PM2",String(PM2),false);
    delay(3000);
  }

    if (hasTVOC) {
    if (hasPM) payload=payload+",";
    int TVOC = SGP.getTVOC();
    payload=payload+"\"tvoc\":" + String(TVOC);
    showTextRectangle("TVOC",String(TVOC),false);
    delay(3000);
  }

  if (hasCO2) {
    if (hasTVOC) payload=payload+",";
    int CO2 = ag.getCO2_Raw();
    payload=payload+"\"rco2\":" + String(CO2);
    showTextRectangle("CO2",String(CO2),false);
    delay(3000);
  }

  if (hasSHT) {
    if (hasCO2 || hasPM) payload=payload+",";
    TMP_RH result = ag.periodicFetchData();
    payload=payload+"\"atmp\":" + String(result.t) +   ",\"rhum\":" + String(result.rh);
    showTextRectangle(String(result.t),String(result.rh)+"%",false);
    delay(3000);
  }

   payload=payload+"}";

  // send payload
  if (connectWIFI){
  Serial.println(payload);
  String POSTURL = APIROOT + "sensors/airgradient:" + String(ESP.getChipId(),HEX) + "/measures";
  Serial.println(POSTURL);
  WiFiClient client;
  HTTPClient http;
  http.begin(client, POSTURL);
  http.addHeader("content-type", "application/json");
  int httpCode = http.POST(payload);
  String response = http.getString();
  Serial.println(httpCode);
  Serial.println(response);
  http.end();
  }
}

// DISPLAY
void showTextRectangle(String ln1, String ln2, boolean small) {
  display.clear();
  display.setTextAlignment(TEXT_ALIGN_LEFT);
  if (small) {
    display.setFont(ArialMT_Plain_16);
  } else {
    display.setFont(ArialMT_Plain_24);
  }
  display.drawString(32, 16, ln1);
  display.drawString(32, 36, ln2);
  display.display();
}

// Wifi Manager
void connectToWifi(){
  WiFiManager wifiManager;
  //WiFi.disconnect(); //to delete previous saved hotspot
  String HOTSPOT = "AIRGRADIENT-"+String(ESP.getChipId(),HEX);
  wifiManager.setTimeout(120);
  if(!wifiManager.autoConnect((const char*)HOTSPOT.c_str())) {
      Serial.println("failed to connect and hit timeout");
      delay(3000);
      ESP.restart();
      delay(5000);
  }

}