esp32-env-monitor/esp32-env-monitor.ino

#include <Arduino.h>
#include <Wire.h>
#include <Preferences.h>
#include <Ticker.h>

#include <WiFi.h>
#include "wifi_login.h"
#include <WebServer.h>

#include <U8g2lib.h>

#ifdef U8X8_HAVE_HW_SPI
#include <SPI.h>
#endif

#include <BME280I2C.h>

#include <Adafruit_SGP30.h>

WebServer server(80);

Preferences preferences;

Ticker metricsReader;
Ticker baselineReader;

U8G2_SSD1327_WS_128X128_1_4W_HW_SPI u8g2(U8G2_R0, /* cs=*/ 17, /* dc=*/ 3, /* reset=*/ 16);


/* Based on Bosch BME280I2C environmental sensor data sheet.
Weather Monitoring :
   forced mode, 1 sample/minute
   pressure ×1, temperature ×1, humidity ×1, filter off
   Current Consumption =  0.16 μA
   RMS Noise = 3.3 Pa/30 cm, 0.07 %RH
   Data Output Rate 1/60 Hz */

BME280I2C::Settings settings(
   BME280::OSR_X1,
   BME280::OSR_X1,
   BME280::OSR_X1,
   BME280::Mode_Forced,
   BME280::StandbyTime_1000ms,
   BME280::Filter_Off,
   BME280::SpiEnable_False,
   BME280I2C::I2CAddr_0x76 // I2C address. I2C specific.
);

BME280I2C bme(settings);

Adafruit_SGP30 sgp;

// setup the terminal (U8G2LOG) and connect to u8g2 for automatic refresh of the display
// The size (width * height) depends on the display
// u8g2_font_t0_15_mf: BBX Width 8, Height 15
// 128/8 = 16
#define U8LOG_WIDTH 16
// 128/15 = 8
#define U8LOG_HEIGHT 8
uint8_t u8log_buffer[U8LOG_WIDTH*U8LOG_HEIGHT];
U8G2LOG u8g2log;

/* return absolute humidity [mg/m^3] with approximation formula
* @param temperature [°C]
* @param humidity [%RH]
*/
uint32_t getAbsoluteHumidity(float temperature, float humidity) {
  // approximation formula from Sensirion SGP30 Driver Integration chapter 3.15
  const float absoluteHumidity = 216.7f * ((humidity / 100.0f) * 6.112f * exp((17.62f * temperature) / (243.12f + temperature)) / (273.15f + temperature)); // [g/m^3]
  const uint32_t absoluteHumidityScaled = static_cast<uint32_t>(1000.0f * absoluteHumidity); // [mg/m^3]
  return absoluteHumidityScaled;
}

BME280::TempUnit tempUnit(BME280::TempUnit_Celsius);
BME280::PresUnit presUnit(BME280::PresUnit_hPa);
float temp(NAN), hum(NAN), pres(NAN);
uint16_t TVOC_base, eCO2_base;
bool baseline_set = false;

void readMetrics() {

  //Clear screen
  u8g2log.print("\f");

  //Read Temperature, humidity and pressure
  bme.read(pres, temp, hum, tempUnit, presUnit);

  //Read Air Quality
  sgp.setHumidity(getAbsoluteHumidity(temp, hum));

  if (! sgp.IAQmeasure()) {
    u8g2log.print("Air Quality Measurement failed\n");
    return;
  }

  u8g2log.print("Temp: ");
  u8g2log.print(temp);
  u8g2log.print("°"+ String(tempUnit == BME280::TempUnit_Celsius ? 'C' :'F'));
  u8g2log.print("\nHum: ");
  u8g2log.print(hum);
  u8g2log.print("% RH");
  u8g2log.print("\nPres: ");
  u8g2log.print(pres);
  u8g2log.print("hPa\n");

  u8g2log.print("TVOC ");
  u8g2log.print(sgp.TVOC);
  u8g2log.print(" ppb\n");
  u8g2log.print("eCO2 ");
  u8g2log.print(sgp.eCO2);
  u8g2log.print(" ppm\n");

}

void readBaseline() {

  if (! sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) {
    u8g2log.print("Failed to get baseline readings\n");
    return;
  }
  u8g2log.print("Baseline values: eCO2: 0x");
  u8g2log.print(eCO2_base, HEX);
  u8g2log.print(" & TVOC: 0x");
  u8g2log.print(TVOC_base, HEX);
  u8g2log.print("\n");

  //Init Non Volatile Storage
  // Namespace name is limited to 15 chars.
  // RW-mode (second parameter has to be false).
  preferences.begin("env-monitor", false);
  preferences.putBool("baseline_set",true);

  preferences.putUShort("TVOC_base", TVOC_base);
  preferences.putUShort("eCO2_base", eCO2_base);

  preferences.end();

  //Next baseline reading in 1h
  baselineReader.once(3600, readBaseline);

}

void sendMetrics() {
  String message = "# ESP32 Env monitor Prometheus metrics\n\n";

  float temperature = temp;
  float humidity = hum;
  float pressure = pres;

  if (temperature < 100) {
    message += "# HELP env_temperature The temperature in " + String(tempUnit == BME280::TempUnit_Celsius ? 'C' :'F') + "\n";
    message += "# TYPE env_temperature gauge\n";
    message += "env_temperature " + String(temperature) + "\n\n";
  }

  if (pressure < 2000) {
    message += "# HELP env_pressure The pressure in " + String(presUnit) + "\n";
    message += "# TYPE env_pressure gauge\n";
    message += "env_pressure " + String(pressure) + "\n\n";
  }

  if (humidity < 100){
    message += "# HELP env_humidity The humidity in %\n";
    message += "# TYPE env_humidity gauge\n";
    message += "env_humidity " + String(humidity) + "\n\n";
  }

  message += "# HELP env_tvoc The TVOC in ppb\n";
  message += "# TYPE env_tvoc gauge\n";
  message += "env_tvoc " + String(sgp.TVOC) + "\n\n";

  message += "# HELP env_eco2 The eCO2 in ppb\n";
  message += "# TYPE env_eco2 gauge\n";
  message += "env_eco2 " + String(sgp.eCO2) + "\n\n";

  server.send(200, "text/plain; version=0.0.4", message);
}

void setup() {

  //Init Display
  u8g2.begin();
  u8g2.setFont(u8g2_font_t0_15_mf);
  u8g2.enableUTF8Print();

  u8g2log.begin(u8g2, U8LOG_WIDTH, U8LOG_HEIGHT, u8log_buffer);
  u8g2log.setLineHeightOffset(0);	// set extra space between lines in pixel, this can be negative
  u8g2log.setRedrawMode(0);		// 0: Update screen with newline, 1: Update screen for every char


  //Init wifi connection
  WiFi.begin(ssid, password);

  u8g2log.print("Connecting to:\n");
  u8g2log.print(ssid);
  u8g2log.print("\n");
  u8g2log.print("\n");

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    u8g2log.print(".");
  }

  u8g2log.print("\n");
  u8g2log.print("WiFi connected\n");
  u8g2log.print("IP address:\n");
  u8g2log.println(WiFi.localIP());
  u8g2log.print("\n");
  u8g2log.print("\n");

  //Init Server
  server.on("/",
    []() {
      server.send(200, "text/plain", "Welcome to the Env Monitor!\n");
    }
  );
  server.on("/metrics", sendMetrics);
  server.onNotFound(
    []() {
      server.send(404, "text/plain", "Content not found\n");
    }
  );
  server.begin();

  //Init BME280 sensor
  Wire.begin();

  while(!bme.begin()) {
    u8g2log.print("Could not find BME280 sensor!\n");
    delay(1000);
  }

  switch(bme.chipModel()) {
    case BME280::ChipModel_BME280:
      u8g2log.print("Found BME280 sensor! Success.\n");
      break;
    case BME280::ChipModel_BMP280:
      u8g2log.print("Found BMP280 sensor! No Humidity available.\n");
      break;
    default:
      u8g2log.print("Found UNKNOWN sensor! Error!\n");
  }


  //Init SGP30 sensor
  while(!sgp.begin()) {
    u8g2log.print("Could not find SGP30 sensor!\n");
    delay(1000);
  }

  u8g2log.print("Found SGP30 serial #");
  u8g2log.print(sgp.serialnumber[0], HEX);
  u8g2log.print(sgp.serialnumber[1], HEX);
  u8g2log.print(sgp.serialnumber[2], HEX);
  u8g2log.print("\n");

  if (! sgp.IAQinit()){
    u8g2log.print("Failed to init IAQ algorithm\n");
  }

  //Init Non Volatile Storage
  // Namespace name is limited to 15 chars.
  // RW-mode (second parameter has to be false).
  preferences.begin("env-monitor", false);

  baseline_set = preferences.getBool("baseline_set",false);
  if (baseline_set){
    TVOC_base = preferences.getUShort("TVOC_base",0);
    eCO2_base = preferences.getUShort("eCO2_base",0);
    if ( TVOC_base != 0 && eCO2_base != 0){
      // If you have a baseline measurement from before you can assign it to start, to 'self-calibrate'
      u8g2log.print("Found previous baseline\n");
      sgp.setIAQBaseline(eCO2_base, TVOC_base);
      u8g2log.print("Baseline values: eCO2: 0x");
      u8g2log.print(eCO2_base, HEX);
      u8g2log.print(" & TVOC: 0x");
      u8g2log.print(TVOC_base, HEX);
      u8g2log.print("\n");
    }
  }

  preferences.end();

  //delay to allow setup output reading
  delay(10000);

  //read Metrics once
  readMetrics();

  //and then read Metrics every minutes
  metricsReader.attach(60, readMetrics);

  //First baseline reading after 12 hours
  baselineReader.once(3600 * 12, readBaseline);

}


void loop() {

  //detect connection lost and reconnect
  if (WiFi.status() != WL_CONNECTED) {
      u8g2log.print("WiFi lost connection.\n");

      delay(500);
      WiFi.begin(ssid, password);

      u8g2log.print("Reconnecting to:\n");
      u8g2log.print(ssid);
      u8g2log.print("\n");
      u8g2log.print("\n");

      while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        u8g2log.print(".");
      }

  };

  server.handleClient();

}

// vim: set ts=2 sw=2 et: