From a794de5eb8275690f8d90620cd19ab13829eced6 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Tue, 30 Mar 2021 17:57:27 +0200
Subject: [PATCH 1/8] add bme280

---
 lib/MQ135/MQ135.cpp |  17 +------
 lib/MQ135/MQ135.h   |   2 +-
 platformio.ini      |   6 +--
 src/main.cpp        |  98 +++++++++++++++++---------------------
 test/main.cpp       | 112 ++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 159 insertions(+), 76 deletions(-)
 create mode 100644 test/main.cpp

diff --git a/lib/MQ135/MQ135.cpp b/lib/MQ135/MQ135.cpp
index 676ed31..1da60a4 100644
--- a/lib/MQ135/MQ135.cpp
+++ b/lib/MQ135/MQ135.cpp
@@ -3,13 +3,10 @@
 @file     MQ135.cpp
 @author   G.Krocker (Mad Frog Labs)
 @license  GNU GPLv3
-
 First version of an Arduino Library for the MQ135 gas sensor
 TODO: Review the correction factor calculation. This currently relies on
 the datasheet but the information there seems to be wrong.
-
 @section  HISTORY
-
 v1.0 - First release
 */
 /**************************************************************************/
@@ -19,7 +16,6 @@ v1.0 - First release
 /**************************************************************************/
 /*!
 @brief  Default constructor
-
 @param[in] pin  The analog input pin for the readout of the sensor
 */
 /**************************************************************************/
@@ -32,10 +28,8 @@ MQ135::MQ135(uint8_t pin) {
 /**************************************************************************/
 /*!
 @brief  Get the correction factor to correct for temperature and humidity
-
 @param[in] t  The ambient air temperature
 @param[in] h  The relative humidity
-
 @return The calculated correction factor
 */
 /**************************************************************************/
@@ -46,7 +40,6 @@ float MQ135::getCorrectionFactor(float t, float h) {
 /**************************************************************************/
 /*!
 @brief  Get the resistance of the sensor, ie. the measurement value
-
 @return The sensor resistance in kOhm
 */
 /**************************************************************************/
@@ -59,10 +52,8 @@ float MQ135::getResistance() {
 /*!
 @brief  Get the resistance of the sensor, ie. the measurement value corrected
         for temp/hum
-
 @param[in] t  The ambient air temperature
 @param[in] h  The relative humidity
-
 @return The corrected sensor resistance kOhm
 */
 /**************************************************************************/
@@ -73,7 +64,6 @@ float MQ135::getCorrectedResistance(float t, float h) {
 /**************************************************************************/
 /*!
 @brief  Get the ppm of CO2 sensed (assuming only CO2 in the air)
-
 @return The ppm of CO2 in the air
 */
 /**************************************************************************/
@@ -85,10 +75,8 @@ float MQ135::getPPM() {
 /*!
 @brief  Get the ppm of CO2 sensed (assuming only CO2 in the air), corrected
         for temp/hum
-
 @param[in] t  The ambient air temperature
 @param[in] h  The relative humidity
-
 @return The ppm of CO2 in the air
 */
 /**************************************************************************/
@@ -99,7 +87,6 @@ float MQ135::getCorrectedPPM(float t, float h) {
 /**************************************************************************/
 /*!
 @brief  Get the resistance RZero of the sensor for calibration purposes
-
 @return The sensor resistance RZero in kOhm
 */
 /**************************************************************************/
@@ -111,13 +98,11 @@ float MQ135::getRZero() {
 /*!
 @brief  Get the corrected resistance RZero of the sensor for calibration
         purposes
-
 @param[in] t  The ambient air temperature
 @param[in] h  The relative humidity
-
 @return The corrected sensor resistance RZero in kOhm
 */
 /**************************************************************************/
 float MQ135::getCorrectedRZero(float t, float h) {
   return getCorrectedResistance(t, h) * pow((ATMOCO2/PARA), (1./PARB));
-}
+}
\ No newline at end of file
diff --git a/lib/MQ135/MQ135.h b/lib/MQ135/MQ135.h
index 1ac6080..9d09441 100644
--- a/lib/MQ135/MQ135.h
+++ b/lib/MQ135/MQ135.h
@@ -25,7 +25,7 @@ v1.0 - First release
 #define RLOAD 10.0
 /// Calibration resistance at atmospheric CO2 level
 // #define RZERO 76.63
-#define RZERO 480
+#define RZERO 4000
 /// Parameters for calculating ppm of CO2 from sensor resistance
 #define PARA 116.6020682
 #define PARB 2.769034857
diff --git a/platformio.ini b/platformio.ini
index ea23b77..f0ece6c 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -8,7 +8,7 @@
 ; Please visit documentation for the other options and examples
 ; https://docs.platformio.org/page/projectconf.html
 
-[env:uno]
+[env:mega]
 platform = atmelavr
-board = uno
-framework = arduino
+board = megaatmega2560
+framework = arduino
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 158386b..5716e7a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,10 +1,9 @@
 #include <Arduino.h>
 #include <MQ135.h>
-#include <dht.h>
+#include <Adafruit_Sensor.h>
+#include <Adafruit_BME280.h>
 
 #define PIN_MQ135 A0
-#define PIN_DHT11 A1
-
 #define PIN_LED_GREEN DD2
 #define PIN_LED_YELLOW DD3
 #define PIN_LED_RED DD4
@@ -13,74 +12,38 @@
 #define MEASURE_DELAY 1000
 #define NOISE_DELAY 100
 
+#define SEALEVELPRESSURE_HPA (1013.25)
+
 MQ135 co2_sensor = MQ135(PIN_MQ135);
-dht dht_sensor;
+Adafruit_BME280 bme(10, 11, 12, 13);
 const int maxCount = MEASURE_DELAY / NOISE_DELAY;
-int count = 0;
-float ppm = -1;
+int count = -1;
+float ppm = 0;
 bool noise = false;
 
 void setup() {
-  Serial.begin(9600);
   pinMode(PIN_MQ135, INPUT);
-  pinMode(PIN_DHT11, INPUT);
   pinMode(PIN_LED_GREEN, OUTPUT);
   pinMode(PIN_LED_YELLOW, OUTPUT);
   pinMode(PIN_LED_RED, OUTPUT);
   pinMode(PIN_NOISE, OUTPUT);
-}
 
-float measure() {
-  Serial.print(RZERO);
-  Serial.println("---------------------------");
-  Serial.print("DHT:\t");
-  int chk = dht_sensor.read11(PIN_DHT11);
-  switch (chk)
-  {
-    case DHTLIB_OK:  
-      Serial.print("OK,\t"); 
-      break;
-    case DHTLIB_ERROR_CHECKSUM: 
-      Serial.print("Checksum error,\t"); 
-      break;
-    case DHTLIB_ERROR_TIMEOUT: 
-      Serial.print("Time out error,\t"); 
-      break;
-    case DHTLIB_ERROR_CONNECT:
-        Serial.print("Connect error,\t");
-        break;
-    case DHTLIB_ERROR_ACK_L:
-        Serial.print("Ack Low error,\t");
-        break;
-    case DHTLIB_ERROR_ACK_H:
-        Serial.print("Ack High error,\t");
-        break;
-    default: 
-      Serial.print("Unknown error,\t"); 
-      break;
+  Serial.begin(9600);
+
+  if (!bme.begin()) {
+    Serial.println(F("Could not find a valid BME280 sensor, check wiring!"));
   }
-  Serial.println();
-
-  Serial.print ("temperature: ");
-  Serial.println (dht_sensor.temperature);
-  Serial.print ("humidity: ");
-  Serial.println (dht_sensor.humidity);
-
-  float val = analogRead(A0);
-  Serial.print ("raw = ");
-  Serial.println (val);
-  float zero = co2_sensor.getCorrectedRZero(dht_sensor.temperature, dht_sensor.humidity);
-  Serial.print ("rzero: ");
-  Serial.println (zero);
-  float ppm = co2_sensor.getCorrectedPPM(dht_sensor.temperature, dht_sensor.humidity);
-  Serial.print ("ppm: ");
-  Serial.println (ppm);
-  return ppm;
 }
 
+void printValues();
+
 void loop() {
-  if (count >= maxCount || ppm < 0) {
-    ppm = measure();
+  if (count >= maxCount || count < 0) {
+    ppm = co2_sensor.getPPM();
+    Serial.print ("ppm: ");
+    Serial.println (ppm);
+    Serial.print ("rzero: ");
+    Serial.println (co2_sensor.getRZero());
     count = 0;
     if (ppm < 1000) {
       digitalWrite(PIN_LED_GREEN, 1);
@@ -97,6 +60,8 @@ void loop() {
       digitalWrite(PIN_LED_YELLOW, 0);
       digitalWrite(PIN_LED_RED, 1);
     }
+
+    // printValues();
   }
 
   if (ppm > 2000) {
@@ -109,4 +74,25 @@ void loop() {
 
   delay(NOISE_DELAY);
   count++;
+}
+
+void printValues() {
+  Serial.print("Temperature = ");
+  Serial.print(bme.readTemperature());
+  Serial.println(" *C");
+
+  Serial.print("Pressure = ");
+
+  Serial.print(bme.readPressure() / 100.0F);
+  Serial.println(" hPa");
+
+  Serial.print("Approx. Altitude = ");
+  Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
+  Serial.println(" m");
+
+  Serial.print("Humidity = ");
+  Serial.print(bme.readHumidity());
+  Serial.println(" %");
+
+  Serial.println();
 }
\ No newline at end of file
diff --git a/test/main.cpp b/test/main.cpp
new file mode 100644
index 0000000..158386b
--- /dev/null
+++ b/test/main.cpp
@@ -0,0 +1,112 @@
+#include <Arduino.h>
+#include <MQ135.h>
+#include <dht.h>
+
+#define PIN_MQ135 A0
+#define PIN_DHT11 A1
+
+#define PIN_LED_GREEN DD2
+#define PIN_LED_YELLOW DD3
+#define PIN_LED_RED DD4
+#define PIN_NOISE DD5
+
+#define MEASURE_DELAY 1000
+#define NOISE_DELAY 100
+
+MQ135 co2_sensor = MQ135(PIN_MQ135);
+dht dht_sensor;
+const int maxCount = MEASURE_DELAY / NOISE_DELAY;
+int count = 0;
+float ppm = -1;
+bool noise = false;
+
+void setup() {
+  Serial.begin(9600);
+  pinMode(PIN_MQ135, INPUT);
+  pinMode(PIN_DHT11, INPUT);
+  pinMode(PIN_LED_GREEN, OUTPUT);
+  pinMode(PIN_LED_YELLOW, OUTPUT);
+  pinMode(PIN_LED_RED, OUTPUT);
+  pinMode(PIN_NOISE, OUTPUT);
+}
+
+float measure() {
+  Serial.print(RZERO);
+  Serial.println("---------------------------");
+  Serial.print("DHT:\t");
+  int chk = dht_sensor.read11(PIN_DHT11);
+  switch (chk)
+  {
+    case DHTLIB_OK:  
+      Serial.print("OK,\t"); 
+      break;
+    case DHTLIB_ERROR_CHECKSUM: 
+      Serial.print("Checksum error,\t"); 
+      break;
+    case DHTLIB_ERROR_TIMEOUT: 
+      Serial.print("Time out error,\t"); 
+      break;
+    case DHTLIB_ERROR_CONNECT:
+        Serial.print("Connect error,\t");
+        break;
+    case DHTLIB_ERROR_ACK_L:
+        Serial.print("Ack Low error,\t");
+        break;
+    case DHTLIB_ERROR_ACK_H:
+        Serial.print("Ack High error,\t");
+        break;
+    default: 
+      Serial.print("Unknown error,\t"); 
+      break;
+  }
+  Serial.println();
+
+  Serial.print ("temperature: ");
+  Serial.println (dht_sensor.temperature);
+  Serial.print ("humidity: ");
+  Serial.println (dht_sensor.humidity);
+
+  float val = analogRead(A0);
+  Serial.print ("raw = ");
+  Serial.println (val);
+  float zero = co2_sensor.getCorrectedRZero(dht_sensor.temperature, dht_sensor.humidity);
+  Serial.print ("rzero: ");
+  Serial.println (zero);
+  float ppm = co2_sensor.getCorrectedPPM(dht_sensor.temperature, dht_sensor.humidity);
+  Serial.print ("ppm: ");
+  Serial.println (ppm);
+  return ppm;
+}
+
+void loop() {
+  if (count >= maxCount || ppm < 0) {
+    ppm = measure();
+    count = 0;
+    if (ppm < 1000) {
+      digitalWrite(PIN_LED_GREEN, 1);
+      digitalWrite(PIN_LED_YELLOW, 0);
+      digitalWrite(PIN_LED_RED, 0);
+    }
+    else if (ppm <= 2000) {
+      digitalWrite(PIN_LED_GREEN, 0);
+      digitalWrite(PIN_LED_YELLOW, 1);
+      digitalWrite(PIN_LED_RED, 0);
+    }
+    else {
+      digitalWrite(PIN_LED_GREEN, 0);
+      digitalWrite(PIN_LED_YELLOW, 0);
+      digitalWrite(PIN_LED_RED, 1);
+    }
+  }
+
+  if (ppm > 2000) {
+    noise = !noise;
+    digitalWrite(PIN_NOISE, noise);
+  }
+  else {
+    digitalWrite(PIN_NOISE, 0);
+  }
+
+  delay(NOISE_DELAY);
+  count++;
+}
\ No newline at end of file

From 5f9ccca0cf8582d49f632b089dda884937725ab5 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Tue, 30 Mar 2021 19:40:44 +0200
Subject: [PATCH 2/8] use corrected values

---
 lib/MQ135/MQ135.h |  2 +-
 platformio.ini    |  4 +++-
 src/main.cpp      | 34 +++++++++++++++-------------------
 3 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/lib/MQ135/MQ135.h b/lib/MQ135/MQ135.h
index 9d09441..a64e707 100644
--- a/lib/MQ135/MQ135.h
+++ b/lib/MQ135/MQ135.h
@@ -25,7 +25,7 @@ v1.0 - First release
 #define RLOAD 10.0
 /// Calibration resistance at atmospheric CO2 level
 // #define RZERO 76.63
-#define RZERO 4000
+#define RZERO 840
 /// Parameters for calculating ppm of CO2 from sensor resistance
 #define PARA 116.6020682
 #define PARB 2.769034857
diff --git a/platformio.ini b/platformio.ini
index f0ece6c..fa8e979 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -11,4 +11,6 @@
 [env:mega]
 platform = atmelavr
 board = megaatmega2560
-framework = arduino
\ No newline at end of file
+framework = arduino
+lib_deps =
+     adafruit/Adafruit BME280 Library @ ^2.1.2
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 5716e7a..8564855 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -35,15 +35,14 @@ void setup() {
   }
 }
 
-void printValues();
+void printValues(float ppm, float temp, float humidity);
 
 void loop() {
   if (count >= maxCount || count < 0) {
-    ppm = co2_sensor.getPPM();
-    Serial.print ("ppm: ");
-    Serial.println (ppm);
-    Serial.print ("rzero: ");
-    Serial.println (co2_sensor.getRZero());
+    float temp = bme.readTemperature();
+    float humidity = bme.readHumidity();
+    ppm = co2_sensor.getCorrectedPPM(temp, humidity);
+    
     count = 0;
     if (ppm < 1000) {
       digitalWrite(PIN_LED_GREEN, 1);
@@ -61,7 +60,7 @@ void loop() {
       digitalWrite(PIN_LED_RED, 1);
     }
 
-    // printValues();
+    printValues(ppm, temp, humidity);
   }
 
   if (ppm > 2000) {
@@ -76,23 +75,20 @@ void loop() {
   count++;
 }
 
-void printValues() {
+void printValues(float ppm, float temp, float humidity) {
   Serial.print("Temperature = ");
-  Serial.print(bme.readTemperature());
+  Serial.print(temp);
   Serial.println(" *C");
 
-  Serial.print("Pressure = ");
-
-  Serial.print(bme.readPressure() / 100.0F);
-  Serial.println(" hPa");
-
-  Serial.print("Approx. Altitude = ");
-  Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
-  Serial.println(" m");
-
   Serial.print("Humidity = ");
-  Serial.print(bme.readHumidity());
+  Serial.print(humidity);
   Serial.println(" %");
 
+  Serial.print ("ppm = ");
+  Serial.println (ppm);
+
+  Serial.print ("rzero = ");
+  Serial.println (co2_sensor.getCorrectedRZero(temp, humidity));
+
   Serial.println();
 }
\ No newline at end of file

From b0ac32d42343f38ecd9ccaa359db6697d5d95801 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Sat, 3 Apr 2021 16:06:39 +0200
Subject: [PATCH 3/8] custom mq135 api

---
 lib/MQ135New/MQ135New.cpp |  59 ++++++++++++++++++++
 lib/MQ135New/MQ135New.h   |  31 +++++++++++
 platformio.ini            |   5 +-
 src/main.cpp              | 112 ++++++++++++++------------------------
 4 files changed, 135 insertions(+), 72 deletions(-)
 create mode 100644 lib/MQ135New/MQ135New.cpp
 create mode 100644 lib/MQ135New/MQ135New.h

diff --git a/lib/MQ135New/MQ135New.cpp b/lib/MQ135New/MQ135New.cpp
new file mode 100644
index 0000000..ef91a11
--- /dev/null
+++ b/lib/MQ135New/MQ135New.cpp
@@ -0,0 +1,59 @@
+#include "MQ135New.h"
+
+MQ135::MQ135(uint8_t pin) {
+  _pin = pin;
+}
+
+double MQ135::getRS() {
+    double voltage = getVoltage();
+    double RS = (double)((double)(VIn * RL) / voltage) - RL;
+    return RS;
+}
+
+double MQ135::getVoltage() {
+    int value = analogRead(_pin);
+    double voltage = (double)(value * VIn) / (double)(Resolution);
+    return voltage;
+}
+
+double MQ135::getPPM(float a, float b) {
+    double ratio = getRS() / R0;
+    // double ppm_log = (log10(ratio) - b) / a;
+    // double ppm = pow(10, ppm_log);
+    double ppm = a * pow(ratio, b);
+    return ppm;
+}
+
+double MQ135::getAcetona() {
+    return getPPM(34.668, -3.369);
+}
+
+double MQ135::getAlcohol() {
+    return getPPM(77.255, -3.18);
+}
+
+double MQ135::getCO2() {
+    // return getPPM(-0.3525, 0.7142) + ATMOCO2;
+    return getPPM(110.47, -2.862) + ATMOCO2;
+}
+
+double MQ135::getCO() {
+    return getPPM(605.18, -3.937);
+}
+
+double MQ135::getNH4() {
+    return getPPM(102.2, -2.473);
+}
+
+double MQ135::getTolueno() {
+    return getPPM(44.947, -3.445);
+}
+
+float MQ135::getR0() {
+    double r0 = getRS() / 3.6;
+    return r0;
+}
+
+void MQ135::setR0(float r0) {
+    R0 = r0;
+}
diff --git a/lib/MQ135New/MQ135New.h b/lib/MQ135New/MQ135New.h
new file mode 100644
index 0000000..4e1f247
--- /dev/null
+++ b/lib/MQ135New/MQ135New.h
@@ -0,0 +1,31 @@
+#ifndef MQ135New_H
+#define MQ135New_H
+
+#include "Arduino.h"
+
+#define RL 10
+#define VIn 5
+#define Resolution 1024
+
+#define ATMOCO2 397.13
+
+class MQ135 {
+ private:
+  uint8_t _pin;
+  float R0;
+  double getPPM(float a, float b);
+
+ public:
+  MQ135(uint8_t pin);
+  double getAcetona();
+  double getAlcohol();
+  double getCO();
+  double getCO2();
+  double getNH4();
+  double getTolueno();
+  float getR0();
+  void setR0(float r0);
+  double getRS();
+  double getVoltage();
+};
+#endif
diff --git a/platformio.ini b/platformio.ini
index fa8e979..ae5769a 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -12,5 +12,6 @@
 platform = atmelavr
 board = megaatmega2560
 framework = arduino
-lib_deps =
-     adafruit/Adafruit BME280 Library @ ^2.1.2
\ No newline at end of file
+; lib_deps =
+;      adafruit/Adafruit BME280 Library @ ^2.1.2
+;      miguel5612/MQUnifiedsensor @ ^2.0.1
diff --git a/src/main.cpp b/src/main.cpp
index 8564855..1b622b4 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,7 +1,5 @@
 #include <Arduino.h>
-#include <MQ135.h>
-#include <Adafruit_Sensor.h>
-#include <Adafruit_BME280.h>
+#include <MQ135New.h>
 
 #define PIN_MQ135 A0
 #define PIN_LED_GREEN DD2
@@ -12,83 +10,57 @@
 #define MEASURE_DELAY 1000
 #define NOISE_DELAY 100
 
-#define SEALEVELPRESSURE_HPA (1013.25)
-
-MQ135 co2_sensor = MQ135(PIN_MQ135);
-Adafruit_BME280 bme(10, 11, 12, 13);
-const int maxCount = MEASURE_DELAY / NOISE_DELAY;
-int count = -1;
-float ppm = 0;
-bool noise = false;
+MQ135 co2_sensor(PIN_MQ135);
 
 void setup() {
-  pinMode(PIN_MQ135, INPUT);
-  pinMode(PIN_LED_GREEN, OUTPUT);
-  pinMode(PIN_LED_YELLOW, OUTPUT);
-  pinMode(PIN_LED_RED, OUTPUT);
-  pinMode(PIN_NOISE, OUTPUT);
-
   Serial.begin(9600);
-
-  if (!bme.begin()) {
-    Serial.println(F("Could not find a valid BME280 sensor, check wiring!"));
-  }
+  pinMode(PIN_MQ135, INPUT);
+  co2_sensor.setR0(66.0);
 }
 
 void printValues(float ppm, float temp, float humidity);
 
 void loop() {
-  if (count >= maxCount || count < 0) {
-    float temp = bme.readTemperature();
-    float humidity = bme.readHumidity();
-    ppm = co2_sensor.getCorrectedPPM(temp, humidity);
+  float value = co2_sensor.getCO2();
+  Serial.println(value);
+  Serial.print("rs: ");
+  Serial.println(co2_sensor.getRS());
+  Serial.print("voltage: ");
+  Serial.println(co2_sensor.getVoltage());
+  delay(500);
+  // if (count >= maxCount || count < 0) {
+  //   float temp = bme.readTemperature();
+  //   float humidity = bme.readHumidity();
+  //   ppm = co2_sensor.getCorrectedPPM(temp, humidity);
     
-    count = 0;
-    if (ppm < 1000) {
-      digitalWrite(PIN_LED_GREEN, 1);
-      digitalWrite(PIN_LED_YELLOW, 0);
-      digitalWrite(PIN_LED_RED, 0);
-    }
-    else if (ppm <= 2000) {
-      digitalWrite(PIN_LED_GREEN, 0);
-      digitalWrite(PIN_LED_YELLOW, 1);
-      digitalWrite(PIN_LED_RED, 0);
-    }
-    else {
-      digitalWrite(PIN_LED_GREEN, 0);
-      digitalWrite(PIN_LED_YELLOW, 0);
-      digitalWrite(PIN_LED_RED, 1);
-    }
+  //   count = 0;
+  //   if (ppm < 1000) {
+  //     digitalWrite(PIN_LED_GREEN, 1);
+  //     digitalWrite(PIN_LED_YELLOW, 0);
+  //     digitalWrite(PIN_LED_RED, 0);
+  //   }
+  //   else if (ppm <= 2000) {
+  //     digitalWrite(PIN_LED_GREEN, 0);
+  //     digitalWrite(PIN_LED_YELLOW, 1);
+  //     digitalWrite(PIN_LED_RED, 0);
+  //   }
+  //   else {
+  //     digitalWrite(PIN_LED_GREEN, 0);
+  //     digitalWrite(PIN_LED_YELLOW, 0);
+  //     digitalWrite(PIN_LED_RED, 1);
+  //   }
 
-    printValues(ppm, temp, humidity);
-  }
+  //   printValues(ppm, temp, humidity);
+  // }
 
-  if (ppm > 2000) {
-    noise = !noise;
-    digitalWrite(PIN_NOISE, noise);
-  }
-  else {
-    digitalWrite(PIN_NOISE, 0);
-  }
+  // if (ppm > 2000) {
+  //   noise = !noise;
+  //   digitalWrite(PIN_NOISE, noise);
+  // }
+  // else {
+  //   digitalWrite(PIN_NOISE, 0);
+  // }
 
-  delay(NOISE_DELAY);
-  count++;
-}
-
-void printValues(float ppm, float temp, float humidity) {
-  Serial.print("Temperature = ");
-  Serial.print(temp);
-  Serial.println(" *C");
-
-  Serial.print("Humidity = ");
-  Serial.print(humidity);
-  Serial.println(" %");
-
-  Serial.print ("ppm = ");
-  Serial.println (ppm);
-
-  Serial.print ("rzero = ");
-  Serial.println (co2_sensor.getCorrectedRZero(temp, humidity));
-
-  Serial.println();
+  // delay(NOISE_DELAY);
+  // count++;
 }
\ No newline at end of file

From 360211d2c20d9fbda6703827cfc41754d0d478c7 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Sat, 3 Apr 2021 19:21:52 +0200
Subject: [PATCH 4/8] remove comments

---
 lib/MQ135New/MQ135New.cpp | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/MQ135New/MQ135New.cpp b/lib/MQ135New/MQ135New.cpp
index ef91a11..9e6adf0 100644
--- a/lib/MQ135New/MQ135New.cpp
+++ b/lib/MQ135New/MQ135New.cpp
@@ -12,14 +12,12 @@ double MQ135::getRS() {
 
 double MQ135::getVoltage() {
     int value = analogRead(_pin);
-    double voltage = (double)(value * VIn) / (double)(Resolution);
+    double voltage = (double)(value * VIn) / (double)(Resolution - 1);
     return voltage;
 }
 
 double MQ135::getPPM(float a, float b) {
     double ratio = getRS() / R0;
-    // double ppm_log = (log10(ratio) - b) / a;
-    // double ppm = pow(10, ppm_log);
     double ppm = a * pow(ratio, b);
     return ppm;
 }
@@ -33,7 +31,6 @@ double MQ135::getAlcohol() {
 }
 
 double MQ135::getCO2() {
-    // return getPPM(-0.3525, 0.7142) + ATMOCO2;
     return getPPM(110.47, -2.862) + ATMOCO2;
 }
 

From ce1a6273eed3f28b77bae26c0c1666dad6c8cb4d Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Sat, 3 Apr 2021 23:40:27 +0200
Subject: [PATCH 5/8] optimizations

---
 lib/MQ135New/MQ135New.cpp | 29 +++++++++++++++++++----------
 lib/MQ135New/MQ135New.h   | 15 ++++++++++-----
 src/main.cpp              | 13 +++++++++----
 3 files changed, 38 insertions(+), 19 deletions(-)

diff --git a/lib/MQ135New/MQ135New.cpp b/lib/MQ135New/MQ135New.cpp
index 9e6adf0..b81301d 100644
--- a/lib/MQ135New/MQ135New.cpp
+++ b/lib/MQ135New/MQ135New.cpp
@@ -4,21 +4,25 @@ MQ135::MQ135(uint8_t pin) {
   _pin = pin;
 }
 
-double MQ135::getRS() {
-    double voltage = getVoltage();
-    double RS = (double)((double)(VIn * RL) / voltage) - RL;
-    return RS;
+double MQ135::getVoltage() {
+    return (double)analogRead(_pin) * VStep;
 }
 
-double MQ135::getVoltage() {
-    int value = analogRead(_pin);
-    double voltage = (double)(value * VIn) / (double)(Resolution - 1);
-    return voltage;
+double MQ135::getResistance() {
+    double voltage = getVoltage();
+    double rs = ((VIn * RL) / voltage) - RL;
+    if (rs < 0) {
+        rs = 0;
+    }
+    return rs;
 }
 
 double MQ135::getPPM(float a, float b) {
-    double ratio = getRS() / R0;
+    double ratio = getResistance() / R0;
     double ppm = a * pow(ratio, b);
+    if (ppm < 0) {
+        ppm = 0;
+    }
     return ppm;
 }
 
@@ -47,10 +51,15 @@ double MQ135::getTolueno() {
 }
 
 float MQ135::getR0() {
-    double r0 = getRS() / 3.6;
+    double r0 = getResistance() / 3.6;
     return r0;
 }
 
+double MQ135::getR0By(float ppm, float a, float b) {
+    double tmp = (log10(ppm / a) / b) - log10(RL);
+    return pow(10, tmp);
+}
+
 void MQ135::setR0(float r0) {
     R0 = r0;
 }
diff --git a/lib/MQ135New/MQ135New.h b/lib/MQ135New/MQ135New.h
index 4e1f247..46da745 100644
--- a/lib/MQ135New/MQ135New.h
+++ b/lib/MQ135New/MQ135New.h
@@ -9,23 +9,28 @@
 
 #define ATMOCO2 397.13
 
+const double VStep = (double)VIn / (Resolution - 1);
+
 class MQ135 {
  private:
   uint8_t _pin;
   float R0;
-  double getPPM(float a, float b);
 
  public:
   MQ135(uint8_t pin);
+  float getR0();
+  double getR0By(float ppm, float a, float b);
+  void setR0(float r0);
+  
+  double getVoltage();
+  double getResistance();
+  double getPPM(float a, float b);
+
   double getAcetona();
   double getAlcohol();
   double getCO();
   double getCO2();
   double getNH4();
   double getTolueno();
-  float getR0();
-  void setR0(float r0);
-  double getRS();
-  double getVoltage();
 };
 #endif
diff --git a/src/main.cpp b/src/main.cpp
index 1b622b4..b3067b1 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,5 +1,5 @@
 #include <Arduino.h>
-#include <MQ135New.h>
+#include "MQ135New.h"
 
 #define PIN_MQ135 A0
 #define PIN_LED_GREEN DD2
@@ -22,12 +22,17 @@ void printValues(float ppm, float temp, float humidity);
 
 void loop() {
   float value = co2_sensor.getCO2();
+  Serial.print("co2: ");
   Serial.println(value);
-  Serial.print("rs: ");
-  Serial.println(co2_sensor.getRS());
+  Serial.print("resistance: ");
+  Serial.println(co2_sensor.getResistance());
   Serial.print("voltage: ");
   Serial.println(co2_sensor.getVoltage());
-  delay(500);
+  Serial.print("r01: ");
+  Serial.println(co2_sensor.getR0());
+  Serial.print("r02: ");
+  Serial.println(co2_sensor.getR0By(1, 110.47, -2.862));
+  delay(2000);
   // if (count >= maxCount || count < 0) {
   //   float temp = bme.readTemperature();
   //   float humidity = bme.readHumidity();

From fac08df3d143ec391a9a745dd4b4b8d08c462004 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Mon, 5 Apr 2021 16:06:32 +0200
Subject: [PATCH 6/8] add comments

---
 lib/MQ135/MQ135.cpp       | 157 ++++++++++++++++----------------------
 lib/MQ135/MQ135.h         |  94 +++++++++++++----------
 lib/MQ135New/MQ135New.cpp |  65 ----------------
 lib/MQ135New/MQ135New.h   |  36 ---------
 src/main.cpp              |  12 +--
 test/main.cpp             | 112 ---------------------------
 6 files changed, 120 insertions(+), 356 deletions(-)
 delete mode 100644 lib/MQ135New/MQ135New.cpp
 delete mode 100644 lib/MQ135New/MQ135New.h
 delete mode 100644 test/main.cpp

diff --git a/lib/MQ135/MQ135.cpp b/lib/MQ135/MQ135.cpp
index 1da60a4..ef235f7 100644
--- a/lib/MQ135/MQ135.cpp
+++ b/lib/MQ135/MQ135.cpp
@@ -1,108 +1,83 @@
-/**************************************************************************/
-/*!
-@file     MQ135.cpp
-@author   G.Krocker (Mad Frog Labs)
-@license  GNU GPLv3
-First version of an Arduino Library for the MQ135 gas sensor
-TODO: Review the correction factor calculation. This currently relies on
-the datasheet but the information there seems to be wrong.
-@section  HISTORY
-v1.0 - First release
-*/
-/**************************************************************************/
-
 #include "MQ135.h"
 
-/**************************************************************************/
-/*!
-@brief  Default constructor
-@param[in] pin  The analog input pin for the readout of the sensor
-*/
-/**************************************************************************/
-
 MQ135::MQ135(uint8_t pin) {
-  _pin = pin;
+  this->pin = pin;
+  pinMode(pin, INPUT);
 }
 
-
-/**************************************************************************/
-/*!
-@brief  Get the correction factor to correct for temperature and humidity
-@param[in] t  The ambient air temperature
-@param[in] h  The relative humidity
-@return The calculated correction factor
-*/
-/**************************************************************************/
-float MQ135::getCorrectionFactor(float t, float h) {
-  return CORA * t * t - CORB * t + CORC - (h-33.)*CORD;
+double MQ135::getVoltage() {
+    return (double)analogRead(pin) * VStep;
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the resistance of the sensor, ie. the measurement value
-@return The sensor resistance in kOhm
-*/
-/**************************************************************************/
-float MQ135::getResistance() {
-  int val = analogRead(_pin);
-  return ((1023./(float)val) * 5. - 1.)*RLOAD;
+double MQ135::getResistance() {
+    double voltage = getVoltage();
+    double rs = ((VIn * RL) / voltage) - RL;
+    if (rs < 0) {
+        rs = 0;
+    }
+    return rs;
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the resistance of the sensor, ie. the measurement value corrected
-        for temp/hum
-@param[in] t  The ambient air temperature
-@param[in] h  The relative humidity
-@return The corrected sensor resistance kOhm
-*/
-/**************************************************************************/
-float MQ135::getCorrectedResistance(float t, float h) {
-  return getResistance()/getCorrectionFactor(t, h);
+double MQ135::getPPM(float a, float b) {
+    double ratio = getResistance() / R0;
+    double ppm = a * pow(ratio, b);
+    if (ppm < 0) {
+        ppm = 0;
+    }
+    return ppm;
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the ppm of CO2 sensed (assuming only CO2 in the air)
-@return The ppm of CO2 in the air
-*/
-/**************************************************************************/
-float MQ135::getPPM() {
-  return PARA * pow((getResistance()/RZERO), -PARB);
+double MQ135::getPPMLinear(float a, float b) {
+    double ratio = getResistance() / R0;
+    double ppm_log = (log10(ratio) - b) / a;
+    double ppm = pow(10, ppm_log);
+    if (ppm < 0) {
+        ppm = 0;
+    }
+    return ppm;
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the ppm of CO2 sensed (assuming only CO2 in the air), corrected
-        for temp/hum
-@param[in] t  The ambient air temperature
-@param[in] h  The relative humidity
-@return The ppm of CO2 in the air
-*/
-/**************************************************************************/
-float MQ135::getCorrectedPPM(float t, float h) {
-  return PARA * pow((getCorrectedResistance(t, h)/RZERO), -PARB);
+double MQ135::getAcetona() {
+    return getPPM(34.668, -3.369);
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the resistance RZero of the sensor for calibration purposes
-@return The sensor resistance RZero in kOhm
-*/
-/**************************************************************************/
-float MQ135::getRZero() {
-  return getResistance() * pow((ATMOCO2/PARA), (1./PARB));
+double MQ135::getAlcohol() {
+    return getPPM(77.255, -3.18);
 }
 
-/**************************************************************************/
-/*!
-@brief  Get the corrected resistance RZero of the sensor for calibration
-        purposes
-@param[in] t  The ambient air temperature
-@param[in] h  The relative humidity
-@return The corrected sensor resistance RZero in kOhm
-*/
-/**************************************************************************/
-float MQ135::getCorrectedRZero(float t, float h) {
-  return getCorrectedResistance(t, h) * pow((ATMOCO2/PARA), (1./PARB));
-}
\ No newline at end of file
+double MQ135::getCO2() {
+    // return getPPMLinear(-0.3525, 0.7142) + ATMOCO2;
+    return getPPM(110.47, -2.862) + ATMOCO2;
+}
+
+double MQ135::getCO() {
+    return getPPM(605.18, -3.937);
+}
+
+double MQ135::getNH4() {
+    return getPPM(102.2, -2.473);
+}
+
+double MQ135::getTolueno() {
+    return getPPM(44.947, -3.445);
+}
+
+float MQ135::getR0() {
+    double r0 = getResistance() / 3.6;
+    return r0;
+}
+
+double MQ135::getR0ByCO2Level(float ppm) {
+    if (ppm > ATMOCO2) {
+        ppm -= ATMOCO2;
+    }
+    else {
+        return NAN;
+    }
+    double tmp = -(log10(ppm / 110.47) / -2.862) + log10(getResistance());
+    return pow(10, tmp);
+}
+
+void MQ135::setR0(float r0) {
+    R0 = r0;
+}
diff --git a/lib/MQ135/MQ135.h b/lib/MQ135/MQ135.h
index a64e707..c9d980c 100644
--- a/lib/MQ135/MQ135.h
+++ b/lib/MQ135/MQ135.h
@@ -1,56 +1,66 @@
-/**************************************************************************/
-/*!
-@file     MQ135.h
-@author   G.Krocker (Mad Frog Labs)
-@license  GNU GPLv3
+#ifndef MQ135New_H
+#define MQ135New_H
 
-First version of an Arduino Library for the MQ135 gas sensor
-TODO: Review the correction factor calculation. This currently relies on
-the datasheet but the information there seems to be wrong.
+#include "Arduino.h"
 
-@section  HISTORY
+/// Resistor on Sensor in kΩ
+#define RL 10
 
-v1.0 - First release
-*/
-/**************************************************************************/
-#ifndef MQ135_H
-#define MQ135_H
-#if ARDUINO >= 100
- #include "Arduino.h"
-#else
- #include "WProgram.h"
-#endif
+/// Voltage on Sensor in V
+#define VIn 5
 
-/// The load resistance on the board
-#define RLOAD 10.0
-/// Calibration resistance at atmospheric CO2 level
-// #define RZERO 76.63
-#define RZERO 840
-/// Parameters for calculating ppm of CO2 from sensor resistance
-#define PARA 116.6020682
-#define PARB 2.769034857
+/// Board analog Input Resolution
+/// Default: 2^10
+#define Resolution 1024
 
-/// Parameters to model temperature and humidity dependence
-#define CORA 0.00035
-#define CORB 0.02718
-#define CORC 1.39538
-#define CORD 0.0018
-
-/// Atmospheric CO2 level for calibration purposes
+/// CO2 Level in Atmosphere
 #define ATMOCO2 397.13
 
+/// Helper to calculate Voltage from Input
+/// Voltage = input * Vin / (Resolution - 1)
+const double VStep = (double)VIn / (Resolution - 1);
+
 class MQ135 {
  private:
-  uint8_t _pin;
+  /// input pin
+  uint8_t pin;
+  /// calibration Resistance
+  float R0;
 
  public:
+  /// Constructor with analog input Pin
   MQ135(uint8_t pin);
-  float getCorrectionFactor(float t, float h);
-  float getResistance();
-  float getCorrectedResistance(float t, float h);
-  float getPPM();
-  float getCorrectedPPM(float t, float h);
-  float getRZero();
-  float getCorrectedRZero(float t, float h);
+  /// Get R0 in default conditions for calibration purposes.
+  /// Assume CO2 Level is the default Atmospheric Level (~400ppm)
+  float getR0();
+  /// Get R0 in custom conditions for calibration purposes.
+  /// Can be used, if you know the current CO2 Level.
+  double getR0ByCO2Level(float ppm);
+  /// Set R0 Value foir calibration.
+  void setR0(float r0);
+  
+  /// Gets the resolved sensor voltage
+  double getVoltage();
+  /// Calculates the Resistance of the Sensor
+  double getResistance();
+  /// Calculates ppm on a exponential curve
+  /// (Different Gases have different curves)
+  double getPPM(float a, float b);
+  /// Calculates ppm on a linear curve
+  /// (Different Gases have different curves)
+  double getPPMLinear(float a, float b);
+
+  /// Gets ppm of Acetona in Air (C3H6O)
+  double getAcetona();
+  /// Gets ppm of Alcohol in Air
+  double getAlcohol();
+  /// Gets ppm of CO in Air
+  double getCO();
+  /// Gets ppm of CO2 in Air
+  double getCO2();
+  /// Gets ppm of NH4 in Air
+  double getNH4();
+  /// Gets ppm of Tolueno in Air (CH3)
+  double getTolueno();
 };
 #endif
diff --git a/lib/MQ135New/MQ135New.cpp b/lib/MQ135New/MQ135New.cpp
deleted file mode 100644
index b81301d..0000000
--- a/lib/MQ135New/MQ135New.cpp
+++ /dev/null
@@ -1,65 +0,0 @@
-#include "MQ135New.h"
-
-MQ135::MQ135(uint8_t pin) {
-  _pin = pin;
-}
-
-double MQ135::getVoltage() {
-    return (double)analogRead(_pin) * VStep;
-}
-
-double MQ135::getResistance() {
-    double voltage = getVoltage();
-    double rs = ((VIn * RL) / voltage) - RL;
-    if (rs < 0) {
-        rs = 0;
-    }
-    return rs;
-}
-
-double MQ135::getPPM(float a, float b) {
-    double ratio = getResistance() / R0;
-    double ppm = a * pow(ratio, b);
-    if (ppm < 0) {
-        ppm = 0;
-    }
-    return ppm;
-}
-
-double MQ135::getAcetona() {
-    return getPPM(34.668, -3.369);
-}
-
-double MQ135::getAlcohol() {
-    return getPPM(77.255, -3.18);
-}
-
-double MQ135::getCO2() {
-    return getPPM(110.47, -2.862) + ATMOCO2;
-}
-
-double MQ135::getCO() {
-    return getPPM(605.18, -3.937);
-}
-
-double MQ135::getNH4() {
-    return getPPM(102.2, -2.473);
-}
-
-double MQ135::getTolueno() {
-    return getPPM(44.947, -3.445);
-}
-
-float MQ135::getR0() {
-    double r0 = getResistance() / 3.6;
-    return r0;
-}
-
-double MQ135::getR0By(float ppm, float a, float b) {
-    double tmp = (log10(ppm / a) / b) - log10(RL);
-    return pow(10, tmp);
-}
-
-void MQ135::setR0(float r0) {
-    R0 = r0;
-}
diff --git a/lib/MQ135New/MQ135New.h b/lib/MQ135New/MQ135New.h
deleted file mode 100644
index 46da745..0000000
--- a/lib/MQ135New/MQ135New.h
+++ /dev/null
@@ -1,36 +0,0 @@
-#ifndef MQ135New_H
-#define MQ135New_H
-
-#include "Arduino.h"
-
-#define RL 10
-#define VIn 5
-#define Resolution 1024
-
-#define ATMOCO2 397.13
-
-const double VStep = (double)VIn / (Resolution - 1);
-
-class MQ135 {
- private:
-  uint8_t _pin;
-  float R0;
-
- public:
-  MQ135(uint8_t pin);
-  float getR0();
-  double getR0By(float ppm, float a, float b);
-  void setR0(float r0);
-  
-  double getVoltage();
-  double getResistance();
-  double getPPM(float a, float b);
-
-  double getAcetona();
-  double getAlcohol();
-  double getCO();
-  double getCO2();
-  double getNH4();
-  double getTolueno();
-};
-#endif
diff --git a/src/main.cpp b/src/main.cpp
index b3067b1..9d02e87 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,5 +1,5 @@
 #include <Arduino.h>
-#include "MQ135New.h"
+#include "MQ135.h"
 
 #define PIN_MQ135 A0
 #define PIN_LED_GREEN DD2
@@ -15,7 +15,7 @@ MQ135 co2_sensor(PIN_MQ135);
 void setup() {
   Serial.begin(9600);
   pinMode(PIN_MQ135, INPUT);
-  co2_sensor.setR0(66.0);
+  co2_sensor.setR0(1000.);
 }
 
 void printValues(float ppm, float temp, float humidity);
@@ -24,14 +24,6 @@ void loop() {
   float value = co2_sensor.getCO2();
   Serial.print("co2: ");
   Serial.println(value);
-  Serial.print("resistance: ");
-  Serial.println(co2_sensor.getResistance());
-  Serial.print("voltage: ");
-  Serial.println(co2_sensor.getVoltage());
-  Serial.print("r01: ");
-  Serial.println(co2_sensor.getR0());
-  Serial.print("r02: ");
-  Serial.println(co2_sensor.getR0By(1, 110.47, -2.862));
   delay(2000);
   // if (count >= maxCount || count < 0) {
   //   float temp = bme.readTemperature();
diff --git a/test/main.cpp b/test/main.cpp
deleted file mode 100644
index 158386b..0000000
--- a/test/main.cpp
+++ /dev/null
@@ -1,112 +0,0 @@
-#include <Arduino.h>
-#include <MQ135.h>
-#include <dht.h>
-
-#define PIN_MQ135 A0
-#define PIN_DHT11 A1
-
-#define PIN_LED_GREEN DD2
-#define PIN_LED_YELLOW DD3
-#define PIN_LED_RED DD4
-#define PIN_NOISE DD5
-
-#define MEASURE_DELAY 1000
-#define NOISE_DELAY 100
-
-MQ135 co2_sensor = MQ135(PIN_MQ135);
-dht dht_sensor;
-const int maxCount = MEASURE_DELAY / NOISE_DELAY;
-int count = 0;
-float ppm = -1;
-bool noise = false;
-
-void setup() {
-  Serial.begin(9600);
-  pinMode(PIN_MQ135, INPUT);
-  pinMode(PIN_DHT11, INPUT);
-  pinMode(PIN_LED_GREEN, OUTPUT);
-  pinMode(PIN_LED_YELLOW, OUTPUT);
-  pinMode(PIN_LED_RED, OUTPUT);
-  pinMode(PIN_NOISE, OUTPUT);
-}
-
-float measure() {
-  Serial.print(RZERO);
-  Serial.println("---------------------------");
-  Serial.print("DHT:\t");
-  int chk = dht_sensor.read11(PIN_DHT11);
-  switch (chk)
-  {
-    case DHTLIB_OK:  
-      Serial.print("OK,\t"); 
-      break;
-    case DHTLIB_ERROR_CHECKSUM: 
-      Serial.print("Checksum error,\t"); 
-      break;
-    case DHTLIB_ERROR_TIMEOUT: 
-      Serial.print("Time out error,\t"); 
-      break;
-    case DHTLIB_ERROR_CONNECT:
-        Serial.print("Connect error,\t");
-        break;
-    case DHTLIB_ERROR_ACK_L:
-        Serial.print("Ack Low error,\t");
-        break;
-    case DHTLIB_ERROR_ACK_H:
-        Serial.print("Ack High error,\t");
-        break;
-    default: 
-      Serial.print("Unknown error,\t"); 
-      break;
-  }
-  Serial.println();
-
-  Serial.print ("temperature: ");
-  Serial.println (dht_sensor.temperature);
-  Serial.print ("humidity: ");
-  Serial.println (dht_sensor.humidity);
-
-  float val = analogRead(A0);
-  Serial.print ("raw = ");
-  Serial.println (val);
-  float zero = co2_sensor.getCorrectedRZero(dht_sensor.temperature, dht_sensor.humidity);
-  Serial.print ("rzero: ");
-  Serial.println (zero);
-  float ppm = co2_sensor.getCorrectedPPM(dht_sensor.temperature, dht_sensor.humidity);
-  Serial.print ("ppm: ");
-  Serial.println (ppm);
-  return ppm;
-}
-
-void loop() {
-  if (count >= maxCount || ppm < 0) {
-    ppm = measure();
-    count = 0;
-    if (ppm < 1000) {
-      digitalWrite(PIN_LED_GREEN, 1);
-      digitalWrite(PIN_LED_YELLOW, 0);
-      digitalWrite(PIN_LED_RED, 0);
-    }
-    else if (ppm <= 2000) {
-      digitalWrite(PIN_LED_GREEN, 0);
-      digitalWrite(PIN_LED_YELLOW, 1);
-      digitalWrite(PIN_LED_RED, 0);
-    }
-    else {
-      digitalWrite(PIN_LED_GREEN, 0);
-      digitalWrite(PIN_LED_YELLOW, 0);
-      digitalWrite(PIN_LED_RED, 1);
-    }
-  }
-
-  if (ppm > 2000) {
-    noise = !noise;
-    digitalWrite(PIN_NOISE, noise);
-  }
-  else {
-    digitalWrite(PIN_NOISE, 0);
-  }
-
-  delay(NOISE_DELAY);
-  count++;
-}
\ No newline at end of file

From 703f5e6d1aa0f2d3cc8355c4cd9254da21cff1c0 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Mon, 5 Apr 2021 17:25:15 +0200
Subject: [PATCH 7/8] typo

---
 lib/MQ135/MQ135.h | 2 +-
 src/main.cpp      | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/MQ135/MQ135.h b/lib/MQ135/MQ135.h
index c9d980c..4f3d0fe 100644
--- a/lib/MQ135/MQ135.h
+++ b/lib/MQ135/MQ135.h
@@ -36,7 +36,7 @@ class MQ135 {
   /// Get R0 in custom conditions for calibration purposes.
   /// Can be used, if you know the current CO2 Level.
   double getR0ByCO2Level(float ppm);
-  /// Set R0 Value foir calibration.
+  /// Set R0 Value for calibration.
   void setR0(float r0);
   
   /// Gets the resolved sensor voltage
diff --git a/src/main.cpp b/src/main.cpp
index 9d02e87..ace9e9e 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,5 +1,5 @@
 #include <Arduino.h>
-#include "MQ135.h"
+#include <MQ135.h>
 
 #define PIN_MQ135 A0
 #define PIN_LED_GREEN DD2
@@ -14,8 +14,7 @@ MQ135 co2_sensor(PIN_MQ135);
 
 void setup() {
   Serial.begin(9600);
-  pinMode(PIN_MQ135, INPUT);
-  co2_sensor.setR0(1000.);
+  // co2_sensor.setR0(1000.);
 }
 
 void printValues(float ppm, float temp, float humidity);

From 69895ad82481e3c88697cbc32bc3737579966717 Mon Sep 17 00:00:00 2001
From: GrafZeppelin <grafzeppelin@gamlo.de>
Date: Thu, 8 Apr 2021 17:59:50 +0200
Subject: [PATCH 8/8] complete program

---
 src/main.cpp | 76 +++++++++++++++++++++++++++-------------------------
 1 file changed, 39 insertions(+), 37 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index ace9e9e..133cbca 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -10,53 +10,55 @@
 #define MEASURE_DELAY 1000
 #define NOISE_DELAY 100
 
+const int maxCount = 10;
+int count = 0;
+bool noise = false;
+bool noiseActive = false;
+
+float ppm;
+
 MQ135 co2_sensor(PIN_MQ135);
 
 void setup() {
   Serial.begin(9600);
-  // co2_sensor.setR0(1000.);
+  co2_sensor.setR0(100);
 }
 
 void printValues(float ppm, float temp, float humidity);
 
 void loop() {
-  float value = co2_sensor.getCO2();
-  Serial.print("co2: ");
-  Serial.println(value);
-  delay(2000);
-  // if (count >= maxCount || count < 0) {
-  //   float temp = bme.readTemperature();
-  //   float humidity = bme.readHumidity();
-  //   ppm = co2_sensor.getCorrectedPPM(temp, humidity);
+  if (count >= maxCount || count < 0) {
+    ppm = co2_sensor.getCO2();
     
-  //   count = 0;
-  //   if (ppm < 1000) {
-  //     digitalWrite(PIN_LED_GREEN, 1);
-  //     digitalWrite(PIN_LED_YELLOW, 0);
-  //     digitalWrite(PIN_LED_RED, 0);
-  //   }
-  //   else if (ppm <= 2000) {
-  //     digitalWrite(PIN_LED_GREEN, 0);
-  //     digitalWrite(PIN_LED_YELLOW, 1);
-  //     digitalWrite(PIN_LED_RED, 0);
-  //   }
-  //   else {
-  //     digitalWrite(PIN_LED_GREEN, 0);
-  //     digitalWrite(PIN_LED_YELLOW, 0);
-  //     digitalWrite(PIN_LED_RED, 1);
-  //   }
+    count = 0;
+    if (ppm < 1000) {
+      noiseActive = false;
+      digitalWrite(PIN_LED_GREEN, 1);
+      digitalWrite(PIN_LED_YELLOW, 0);
+      digitalWrite(PIN_LED_RED, 0);
+    }
+    else if (ppm <= 2000) {
+      noiseActive = false;
+      digitalWrite(PIN_LED_GREEN, 0);
+      digitalWrite(PIN_LED_YELLOW, 1);
+      digitalWrite(PIN_LED_RED, 0);
+    }
+    else {
+      noiseActive = true;
+      digitalWrite(PIN_LED_GREEN, 0);
+      digitalWrite(PIN_LED_YELLOW, 0);
+      digitalWrite(PIN_LED_RED, 1);
+    }
+  }
 
-  //   printValues(ppm, temp, humidity);
-  // }
+  if (noiseActive) {
+    noise = !noise;
+    digitalWrite(PIN_NOISE, noise);
+  }
+  else {
+    digitalWrite(PIN_NOISE, 0);
+  }
 
-  // if (ppm > 2000) {
-  //   noise = !noise;
-  //   digitalWrite(PIN_NOISE, noise);
-  // }
-  // else {
-  //   digitalWrite(PIN_NOISE, 0);
-  // }
-
-  // delay(NOISE_DELAY);
-  // count++;
+  delay(NOISE_DELAY);
+  count++;
 }
\ No newline at end of file