Arduino Circuit Design using BME680 Sensor

/***************************************************************************
  This is a library for the BME680 gas, humidity, temperature & pressure sensor

  Designed specifically to work with the Adafruit BME680 Breakout
  ----> http://www.adafruit.com/products/3660

  These sensors use I2C or SPI to communicate, 2 or 4 pins are required
  to interface.

  Adafruit invests time and resources providing this open source code,
  please support Adafruit and open-source hardware by purchasing products
  from Adafruit!

  Written by Limor Fried & Kevin Townsend for Adafruit Industries.
  BSD license, all text above must be included in any redistribution

  Code modified for reuse by BiphysicsLab.com using I2C, Serial and LCD output
 ***************************************************************************/

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include "Adafruit_BME680.h"

#include <LiquidCrystal_I2C.h>

#define BME_SCK 13
#define BME_MISO 12
#define BME_MOSI 11
#define BME_CS 10

#define SEALEVELPRESSURE_HPA (1013.25)

// Simple calibration for temperature
#define TEMPOFFSETF -4.85
#define TEMPOFFSETC 0

Adafruit_BME680 bme; // I2C
//Adafruit_BME680 bme(BME_CS); // hardware SPI
//Adafruit_BME680 bme(BME_CS, BME_MOSI, BME_MISO,  BME_SCK);

// Where 0x27 is the LCD I2C address
LiquidCrystal_I2C lcd(0x27, 16, 2);


int pauseTime = 2000; // microseconds between readings
int screenReadings = 5; // readings per screen (T and P, H and G)
int screenCount = 0;

void setup() {
  Serial.begin(9600);
  while (!Serial);
  Serial.println(F("BME680 test"));

  if (!bme.begin()) {
    Serial.println("Could not find a valid BME680 sensor, check wiring!");
    while (1);
  }

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);

  // Set up oversampling and filter initialization
  bme.setTemperatureOversampling(BME680_OS_8X);
  bme.setHumidityOversampling(BME680_OS_2X);
  bme.setPressureOversampling(BME680_OS_4X);
  bme.setIIRFilterSize(BME680_FILTER_SIZE_3);
  bme.setGasHeater(320, 150); // 320*C for 150 ms
}

void loop() {
  if (! bme.performReading()) {
    Serial.println("Failed to perform reading :(");
    return;
  }
  Serial.print("Temperature = ");
  Serial.print(tempConvert(bme.temperature));
  Serial.println(" *F");

  Serial.print("Humidity = ");
  Serial.print(bme.humidity);
  Serial.println(" %");

  Serial.print("Pressure = ");
  Serial.print(pressureConvert(bme.pressure / 100.0));
  Serial.println(" inHg");

  Serial.print("Gas = ");
  Serial.print(bme.gas_resistance / 1000.0);
  Serial.println(" KOhms");

  Serial.print("Approx. Altitude = ");
  Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
  Serial.println(" m");

  if (screenCount < screenReadings)
  {

    if (screenCount == 0)
    {
      lcd.clear();
    }

    lcd.setCursor(0, 0);
    lcd.print("T: ");
    lcd.print(tempConvert(bme.temperature));
    lcd.print(" *F");

    lcd.setCursor(0, 1);
    lcd.print("H: ");
    lcd.print(bme.humidity);
    lcd.print(" %");

  } else if (screenCount < 2 * screenReadings)
  {

    if (screenCount == (screenReadings + 1))
    {
      lcd.clear();
    }

    lcd.setCursor(0, 0);
    lcd.print("P: ");
    lcd.print(pressureConvert(bme.pressure / 100.0));
    lcd.print(" inHg");

    lcd.setCursor(0, 1);
    lcd.print("G: ");
    lcd.print(bme.gas_resistance / 1000.0);
    lcd.print(" KOhms");
  } else

  {
    screenCount = -1;
  }


  Serial.println();
  delay(pauseTime);
  screenCount++;
}

float tempConvert(float T)
{
  // Convert temperature T in degrees C to degrees F
  return T * 1.8 + 32. + TEMPOFFSETF;
}

float pressureConvert(float P)
// Convert pressure P in hPA to in Hg
{
  return P * .030;
}

%% Plot Arduino Serial Port BME680 Results
% Script: ReadSerialDataCaptureTK2.m
% BiophysicsLab.com
% Initial code release: 10/3/2022

%% Create textfile using data output to the Arduino Serial Port
% Where:
%   Data captured in serial port using Ctrl-A followed by Ctrl-C
%   Text file created by pasting captured data into Notepad++ (or other
%   editor).
%   Save text file into same directory as this code
% Read the textfile as a table:
%   Var1 = Time
%   Var3 = Param name (Temperature, Humidity, Pressure, Gas, 'Approx.', ''
%   Var4 = "=", expect for 5'th element which is 'Altitude', ''
%   Var5 = Parameter value (temp, hum, pres, gas, NaN, NaN)
%   Var6 = Param units: *F, %, inHG, KOhms, value for 'approx. altitude',''
%   Var7 = '', '', '', '', parameter units for 'approx. altitude' 'm', ''
% Plot results

% Table values:
%   time entries are in Column 1, Var1, of every row
% Table y values: 
%   Row 1: Column 5, Var5, has the temperature value
%   Row 2: Column 5, Var5, has the humidity value 
%   Row 3: Column 5, Var5, has the pressure value 
%   Row 4: Column 5, Var5, has the gas value 
%   Skip rows 5 and 6
%   Repeat

%% Parameters
tableFileName = 'SerialDataCapture_04.txt'; % name of saved data as text file
tUnits = "Date"; % x-axis time units as a string: "Date" or "Seconds"
xAxisDate = '2022-10-01'; % set date for x-axis plots (when test was run)

disp('readtable');
T = readtable(tableFileName);

%% Plot
figure('Name','Arduino Uno with BME680 Sensor','NumberTitle','off');
% Lay out the four plots (Temperature, Humidity, Pressure, and Gas) 
% in a 2x2 format.
layout = tiledlayout(2,2);
title(layout, 'Arduino Uno with BME680 Sensor')

% Prepare plot time on x-axis
Ttime = T.Var1(1:6:end);
[tDuration, sDuration, elapsedTimeArray] = calculateDuration(Ttime, tUnits);
if tUnits == "Date"
    plotTime = datetime(xAxisDate) + elapsedTimeArray;
    xlabel(layout,'Time (date, hours:minutes:seconds)')
else
    plotTime = elapsedTimeArray;
    xlabel(layout,'Time (seconds)')
end


nexttile % Temperature
plot(plotTime, T.Var5(1:6:end), "Blue")
[yAxisTitleStr, yAxisUnitsStr] = packageAxisInfo(T.Var3(1), T.Var6(1));
title([ yAxisTitleStr ' vs Time'])
ylabel([yAxisTitleStr ' (' yAxisUnitsStr ')'])


nexttile % Humidity
%   first time/humidity entry is row 2, then every 6'th row until eof 
plot(plotTime, T.Var5(2:6:end), "Blue")
[yAxisTitleStr, yAxisUnitsStr] = packageAxisInfo(T.Var3(2), T.Var6(2));
title([ yAxisTitleStr ' vs Time'])
ylabel([yAxisTitleStr ' (' yAxisUnitsStr ')'])


nexttile % Pressure
%   first time/pressure entry is row 3, then every 6'th row until eof 
plot(plotTime, T.Var5(3:6:end), "Blue")
[yAxisTitleStr, yAxisUnitsStr] = packageAxisInfo(T.Var3(3), T.Var6(3));
title([ yAxisTitleStr ' vs Time'])
ylabel([yAxisTitleStr ' (' yAxisUnitsStr ')'])


nexttile % Gas
%   first time/gas entry is row 4, then every 6'th row until eof 
plot(plotTime, T.Var5(4:6:end), "Blue")
[yAxisTitleStr, yAxisUnitsStr] = packageAxisInfo(T.Var3(4), T.Var6(4));
title([ yAxisTitleStr ' vs Time'])
ylabel([yAxisTitleStr ' (' yAxisUnitsStr ')'])



%% Package y-axis title (yAT) and y-axis Units (yAU) from table to chars
% Where:
%   T1 is a y-axis title in cell format
%   T2 is a y-axis units in cell format
function [yAT, yAU] = packageAxisInfo(T1, T2)
    yAT = convertStringsToChars(string(T1));
    yAU = convertStringsToChars(string(T2));
end


%% Package x-axis from table to duration
%   average time step (tTimeStep)
%   standard deviation (stdTimeStep)
%   elapsed time array in tUnits
%   tUnits are "seconds" or "date" case independent
function [tTimeStep, stdTimeStep, elapsedTimeArray] = calculateDuration(timeReadings, tUnits)
    i = 1;
    lengthTimeReadings = length(timeReadings);
    tArray = zeros(1,lengthTimeReadings);
    elapsedTimeArray = tArray;
    while(i<lengthTimeReadings)
        tDiff = timeReadings(i+1)-timeReadings(i);
        if tDiff<0
            tDiff = timeReadings(i+1) + duration(24,0,0) - timeReadings(i);
        end
        tArray(i) = seconds(tDiff);
        if i>1
            elapsedTimeArray(i) = elapsedTimeArray(i-1) + tArray(i);
        else
            elapsedTimeArray(i) = tArray(i);
        end
        i = i + 1;
    end

    tTimeStep = mean(tArray(1:lengthTimeReadings-1)); % Value for my 9 hour test run: 2.8221 ave secs/test
    stdTimeStep = std(tArray(1:lengthTimeReadings-1)); % Value for my 9 hour test run: 0.0215

    % last time difference + average time difference copied to last array time
    % return time in seconds
    elapsedTimeArray(lengthTimeReadings) = elapsedTimeArray(lengthTimeReadings-1) + tTimeStep;
    if lower(tUnits) == "date"
        zinterval = timeReadings(1);
        elapsedTimeArray = zinterval + seconds(elapsedTimeArray);
        elapsedTimeArray.Format = 'dd:hh:mm:ss';
    end
end