#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Define the analog input pins for ESP32
const int mq7Pin = 35;  // GPIO34
const int mq6Pin = 2;
 // GPIO35

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  // Start the serial communication
  Serial.begin(115200);

  // Initialize the LCD
  lcd.init();
  lcd.backlight();
  
  // Print a message to the LCD.
  lcd.setCursor(0, 0);
  lcd.print("MQ7 & MQ6 Sensor");
  delay(2000);
}

void loop() {
  // Read the analog values from the sensors
  int mq7Value = analogRead(mq7Pin);
  int mq6Value = analogRead(mq6Pin);
  
  // Print the sensor values to the Serial Monitor
  Serial.print("MQ-7 Value: ");
  Serial.print(mq7Value);
  Serial.print("\t MQ-6 Value: ");
  Serial.println(mq6Value);
   
  
  // Display sensor values on the LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("MQ-7: ");
  lcd.print(mq7Value);
  lcd.setCursor(0, 1);
  lcd.print("MQ-6: ");
  lcd.print(mq6Value);
  
  
  // Wait for a while before reading the values again
  delay(1000);
}


sketch.ino

diagram.json

mq-7

mq7.chip.json

// Wokwi Custom Chip - For docs and examples see:
// https://docs.wokwi.com/chips-api/getting-started
//
// SPDX-License-Identifier: MIT
// Copyright 2023 Asep Oman Somantri

#include "wokwi-api.h"
#include <stdio.h>
#include <stdlib.h>

// Chip data.
typedef struct 
{
  pin_t VCC;
  pin_t OUT;
  pin_t GND;
  uint32_t adc02;
} chip_data_t;

// Returns true if the power source is connected correctly.
bool power_connected(void *data)
{
  chip_data_t *chip = (chip_data_t*)data;
  return pin_read(chip->VCC) && !pin_read(chip->GND);
}

// Timer function. Analog output based on voltage.
void chip_timer_callback(void *user_data) 
{
  if (power_connected(user_data))
  {
    chip_data_t *chip_data = (chip_data_t*)user_data;
    uint32_t adc02 = attr_read(chip_data->adc02);
    float volts = 0.0008056640625 * adc02;
    pin_dac_write(chip_data->OUT, volts);
  }
}

// Chip initialization.
void chip_init(void) 
{
  chip_data_t *chip_data = malloc(sizeof(chip_data_t));
  chip_data->VCC = pin_init("VCC", INPUT);
  chip_data->GND = pin_init("GND", INPUT);
  chip_data->OUT = pin_init("OUT", ANALOG);
  chip_data->adc02 = attr_init("adc02", 50);

  const timer_config_t config = 
  {
    .callback = chip_timer_callback,
    .user_data = chip_data,
  };

  timer_t timer_id = timer_init(&config);
  timer_start(timer_id, 10000, true);
}

mq7.chip.c

# Wokwi Library List
# See https://docs.wokwi.com/guides/libraries

MQUnifiedsensor
LiquidCrystal I2C
