NodeMCU - Master and UNO - Slaves (I2C communication)

kpuvvala · August 25, 2021, 2:33am

HI GolamMostafa,

Thank you very much for your help. I actually made that to work. However, I am trying to integrate my actual code to this example, but on the master's serial monitor I'm receiving values as "0". I can see all the sensor values on slave serial monitors but not on the master.

My actual plan was to connect three i2c sensors to each slave-UNO and receive the data on Master-NodeMCU(ESP8266) and then send them over to Googlesheets via firebase. Please help me out on this one.

Master - NodeMCU



//--------------------------------firebase-----------------
#include <FirebaseESP8266.h>
#include <esp8266wifi.h>//<ESP8266WiFi.h>
#include "FirebaseESP8266.h"  // Install Firebase ESP8266 library

#define FIREBASE_HOST "***********************************"                     //Your Firebase Project URL goes here without "http:" , "\" and "/"
#define FIREBASE_AUTH "******************" //Your Firebase Database Secret goes here

#define WIFI_SSID "************"
#define WIFI_PASSWORD "*************"
FirebaseData firebaseData;

//--------------------------------reset nodemcu------------------------------
int cnt = 3600;


#include <Wire.h>


float co2ppm1 = 0;
float co2temp1 = 0;
float co2hum1 = 0;
float pressure1 = 0;
float loadvoltage1 = 0;
float current1 = 0;

float co2ppm2 = 0;
float co2temp2 = 0;
float co2hum2 = 0;
float pressure2 = 0;
float loadvoltage2 = 0;
float current2 = 0;


void setup()
{

  //***********************************************************************
  Wire.begin(D4, D3); //SDA=D4, SCL=D3
  Serial.begin(115200);  // start serial for output

  //**************************************************************************************

  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(".");
    delay(300);
  }
  Serial.println();
  Serial.print("Connected with IP: ");
  Serial.println(WiFi.localIP());
  Serial.println();

  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);
  Firebase.reconnectWiFi(true);

  //**************************************************************************************
  Wire.beginTransmission(2);
  byte busStatus = Wire.endTransmission();
  if (busStatus != 0)
  {
    Serial.print("UNO-1 is not found on I2C Bus.");
    while (1);  //wait for ever
  }
  Serial.println("UNO-1 is found on I2C Bus.");

  //**********************************************************************************
  Wire.beginTransmission(8);
  //  byte busStatus = Wire.endTransmission();
  if (busStatus != 0)
  {
    Serial.print("UNO-2 is not found on I2C Bus.");
    while (1);  //wait for ever
  }
  Serial.println("UNO-2 is found on I2C Bus.");
  //**********************************************************************************

  //**********************************************************************************

}

//*************************************************************************************
void loop()
{

  Serial.println(cnt);

  if (cnt == 0) {
    Serial.println("Reset..");
    ESP.restart();
  }

  cnt--;
  delay(1000);
  //***************************************************************************************************


  //***************************************************************************************************

  Wire.requestFrom(2, 40);    // request 37 bytes from slave device #1
  String reactor1, co2ppm1s, co2temp1s, co2hum1s, pressure1s, loadvoltage1s, current1s;
  do   // slave may send less than requested
  {
    char c = Wire.read(); // receive a byte as character

    reactor1 = reactor1 + c; //Keep saving whatever is comming

    co2ppm1s = reactor1.substring(0, 5); //slpit String from 0 to 4
    co2temp1s = reactor1.substring(6, 13); // Split from 5 to 11
    co2hum1s = reactor1. substring(14, 21); // Split from 12 to 19
    pressure1s = reactor1.substring(22, 27); // Split from 20 to 25
    loadvoltage1s = reactor1.substring(28, 33); // Split from 26 to 31
    current1s = reactor1.substring(34, 39); // Split from 32 to 37


  } while (Wire.available());
  Serial.print("Recieving float as String...");
  Serial.println();
  Serial.println();
  Serial.print("Reactor 1 Sensors: ");
  Serial.print(reactor1);

  Serial.println();
  Serial.print("CO2 PPM 1: ");
  Serial.print(co2ppm1s);
  Serial.println();
  Serial.println();

  Serial.print("CO2 TEMP 1: ");
  Serial.print(co2temp1s);
  Serial.println();
  Serial.println();

  Serial.print("CO2 HUM 1: ");
  Serial.print(co2hum1s);
  Serial.println();
  Serial.println();

  Serial.print("Pressure 1: ");
  Serial.print(pressure1s);
  Serial.println();
  Serial.println();

  Serial.print("Load Voltage 1: ");
  Serial.print(loadvoltage1s);
  Serial.println();
  Serial.println();

  Serial.print("Current 1: ");
  Serial.print(current1s);
  Serial.println();
  Serial.println();

  //***************************************************************************************************

  Serial.print("Converting string to float...");
  Serial.println();
  Serial.println();
  co2ppm1 = co2ppm1s.toFloat();
  Serial.print("CO2 PPM 1: ");
  Serial.print(co2ppm1);
  Serial.println();

  co2temp1 = co2temp1s.toFloat();
  Serial.print("CO2 TEMP 1: ");
  Serial.print(co2temp1);
  Serial.println();

  co2hum1 = co2hum1s.toFloat();
  Serial.print("CO2 HUM 1: ");
  Serial.print(co2hum1);
  Serial.println();

  pressure1 = pressure1s.toFloat();
  Serial.print("Pressure 1: ");
  Serial.print(pressure1);
  Serial.println();

  loadvoltage1 = loadvoltage1s.toFloat();
  Serial.print("Load Voltage 1: ");
  Serial.print(loadvoltage1);
  Serial.println();

  current1 = current1s.toFloat();
  Serial.print("Current 1: ");
  Serial.print(current1);
  Serial.println();

  delay(1000);

  //-----------------------------------------firebase-----------------------------------------------

  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);   // connect to firebase
  Firebase.reconnectWiFi(true);



  /////////////Variable One - CO2 Sensor//////////////


  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2 PPM R1", co2ppm1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 = ");
    Serial.println(co2ppm1);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Two - Co2 Humidity Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2Hum R1", co2hum1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 humidity = ");
    Serial.println(co2hum1);
    Serial.println("\n");

    //val++;


  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Three - Co2 Temperature Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2 Temp R1", co2temp1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 temp = ");
    Serial.println(co2temp1);
    Serial.println("\n");

    //val++;
    //  delay(4000);

  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Four - BMP280 Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Pressure R1", pressure1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("hPa = ");
    Serial.println(pressure1);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Five - INA219 loadvoltage//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/INA219 Load Voltage R1", loadvoltage1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("INA219 Load Voltage = ");
    Serial.println(loadvoltage1);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Seven - INA219 Current//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/INA219 Current R1", current1)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("INA219 Current = ");
    Serial.println(current1);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  //**********************************************************************************************

  Wire.requestFrom(8, 40);    // request 37 bytes from slave device #1
  String reactor2, co2ppm2s, co2temp2s, co2hum2s, pressure2s, loadvoltage2s, current2s;
  do   // slave may send less than requested
  {
    char d = Wire.read(); // receive a byte as character

    reactor2 = reactor2 + d; //Keep saving whatever is comming

    co2ppm2s = reactor2.substring(0, 5); //slpit String from 0 to 4
    co2temp2s = reactor2.substring(6, 13); // Split from 5 to 11
    co2hum2s = reactor2. substring(14, 21); // Split from 12 to 19
    pressure2s = reactor2.substring(22, 27); // Split from 20 to 25
    loadvoltage2s = reactor2.substring(28, 33); // Split from 26 to 31
    current2s = reactor2.substring(34, 39); // Split from 32 to 37


  } while (Wire.available());
  Serial.print("Recieving float as String...");
  Serial.println();
  Serial.println();
  Serial.print("Reactor 2 Sensors: ");
  Serial.print(reactor2);

  Serial.println();
  Serial.print("CO2 PPM 2: ");
  Serial.print(co2ppm2s);
  Serial.println();
  Serial.println();

  Serial.print("CO2 TEMP 2: ");
  Serial.print(co2temp2s);
  Serial.println();
  Serial.println();

  Serial.print("CO2 HUM 2: ");
  Serial.print(co2hum2s);
  Serial.println();
  Serial.println();

  Serial.print("Pressure 2: ");
  Serial.print(pressure2s);
  Serial.println();
  Serial.println();

  Serial.print("Load Voltage 2: ");
  Serial.print(loadvoltage2s);
  Serial.println();
  Serial.println();

  Serial.print("Current 2: ");
  Serial.print(current2s);
  Serial.println();
  Serial.println();

  //***************************************************************************************************

  Serial.print("Converting string to float...");
  Serial.println();
  Serial.println();
  co2ppm2 = co2ppm2s.toFloat();
  Serial.print("CO2 PPM 2: ");
  Serial.print(co2ppm2);
  Serial.println();

  co2temp2 = co2temp2s.toFloat();
  Serial.print("CO2 TEMP 2: ");
  Serial.print(co2temp2);
  Serial.println();

  co2hum2 = co2hum2s.toFloat();
  Serial.print("CO2 HUM 2: ");
  Serial.print(co2hum2);
  Serial.println();

  pressure2 = pressure2s.toFloat();
  Serial.print("Pressure 2: ");
  Serial.print(pressure2);
  Serial.println();

  loadvoltage2 = loadvoltage2s.toFloat();
  Serial.print("Load Voltage 2: ");
  Serial.print(loadvoltage2);
  Serial.println();

  current2 = current2s.toFloat();
  Serial.print("Current 2: ");
  Serial.print(current2);
  Serial.println();

  delay(1000);
  //-----------------------------------------firebase-----------------------------------------------

  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);   // connect to firebase
  Firebase.reconnectWiFi(true);



  /////////////Variable Seven - CO2 Sensor//////////////


  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2 PPM R2", co2ppm2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 = ");
    Serial.println(co2ppm2);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Eight - Co2 Humidity Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2Hum R2", co2hum2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 humidity = ");
    Serial.println(co2hum2);
    Serial.println("\n");

    //val++;


  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Nine - Co2 Temperature Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Co2 Temp R2", co2temp2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("Co2 temp = ");
    Serial.println(co2temp2);
    Serial.println("\n");

    //val++;
    //  delay(4000);

  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Ten - BMP280 Sensor//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/Pressure R2", pressure2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("hPa = ");
    Serial.println(pressure2);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Eleven - INA219 loadvoltage//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/INA219 Load Voltage R2", loadvoltage2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("INA219 Load Voltage = ");
    Serial.println(loadvoltage2);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }


  ///////////////Variable Twelve - INA219 Current//////////////

  if (Firebase.setFloat(firebaseData, "Reactors/Array/Data1/INA219 Current R2", current2)) {    // On successful Write operation, function returns 1
    Serial.println("Value Uploaded Successfully");
    Serial.print("INA219 Current = ");
    Serial.println(current2);
    Serial.println("\n");

    //val++;

    //  delay(4000);
  }

  else {
    Serial.println(firebaseData.errorReason());
  }



  //***************************************************************************************************

  //------------------------


  delay(1000);
}

Slave -1(UNO)


#include<Wire.h>
#include <avr/wdt.h>



//**************************************************** SCD30 **************************************************

#include "SparkFun_SCD30_Arduino_Library.h" //Click here to get the library: http://librarymanager/All#SparkFun_SCD30
SCD30 airSensor;

//************************************** BMP280 ***************************************

#include <Adafruit_BMP280.h>
Adafruit_BMP280 bmp; // use I2C interface
Adafruit_Sensor *bmp_temp = bmp.getTemperatureSensor();
Adafruit_Sensor *bmp_pressure = bmp.getPressureSensor();
float array3[1];

//********************************** INA219 ********************************************

#include <Adafruit_INA219.h>
Adafruit_INA219 ina219;
float shuntvoltage = 0;
float busvoltage = 0;

float power_mW = 0;

float array1[3];

//******************************************************************************************

float co21 = 0;
float co2hum1 = 0;
float co2temp1 = 0;
float pressure1 = 0;
float loadvoltage1 = 0;
float current1 = 0;

char co21s[4];
char co2temp1s[8];
char co2hum1s[7];
char pressure1s[6];
char loadvoltage1s[6];
char current1s[6];


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

   for (int i = 5; i > 0; i--) {
    Serial.print(i);
    delay(1000); // I sometimes need a few seconds to restart the serial console.
    wdt_enable(WDTO_4S);
  }

  
  Wire.begin(2);  ////UNO-1/Slave-1 Address
  Wire.onRequest(sendEvent);

  SensorInit(); // Initialize the displays

}

void SensorInit() {

  Serial.println("SCD30 Example");
  Wire.begin();


  if (airSensor.begin() == false)
  {
    Serial.println("Air sensor not detected. Please check wiring. Freezing...");
    while (1)
      ;
  }

  //************************************************************************************

  ina219.begin();
  ina219.setCalibration_16V_400mA(); // set measurement range to 16V, 400mA

  //************************************************************************************

  Serial.println(F("BMP280 Sensor event test"));

  if (!bmp.begin(0x76)) {
    Serial.println(F("Could not find a valid BMP280 sensor, check wiring!"));
    delay(10);
  }


  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,     /* Operating Mode. */
                  Adafruit_BMP280::SAMPLING_X2,     /* Temp. oversampling */
                  Adafruit_BMP280::SAMPLING_X16,    /* Pressure oversampling */
                  Adafruit_BMP280::FILTER_X16,      /* Filtering. */
                  Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */

  bmp_temp->printSensorDetails();

}


void loop()
{

  if (airSensor.dataAvailable())
  {
    Serial.print("co21(ppm):");
    Serial.print(airSensor.getCO2());
    co21 = airSensor.getCO2();


    Serial.print(" temp1(C):");
    Serial.print(airSensor.getTemperature(), 1);
    co2temp1 = airSensor.getTemperature();


    Serial.print(" humidity1(%):");
    Serial.print(airSensor.getHumidity(), 1);
    co2hum1 = airSensor.getHumidity();
    Serial.println();
    Serial.println();

    Serial.println();
    Serial.print(" Pre-stream data");
    Serial.println();
    Serial.print(co21);
    Serial.println();
    Serial.print(co2temp1);
    Serial.println();
    Serial.print(co2hum1);
    Serial.println();

  }

  //****************************************************************************************


  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current1 = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage1 = busvoltage + (shuntvoltage / 1000);

  Serial.println();
  Serial.println();
  Serial.print("Load Voltage 1:  "); Serial.print(loadvoltage1); Serial.println(" V");
  Serial.print("Current 1:       "); Serial.print(current1); Serial.println(" mA");
  Serial.println("");
  Serial.println();
  Serial.println();
  array1[0] = busvoltage;
  array1[1] = shuntvoltage;
  array1[2] = loadvoltage1;
  array1[3] = current1;

  //***************************************************************************************

  sensors_event_t temp_event, pressure_event;
  bmp_temp->getEvent(&temp_event);
  bmp_pressure->getEvent(&pressure_event);

  Serial.println();
  Serial.println();
  Serial.print(F("Temperature = "));
  Serial.print(temp_event.temperature);
  Serial.println(" *C");
  //
  Serial.println();
  Serial.print(F("Pressure = "));
  Serial.print(pressure_event.pressure);
  Serial.println(" hPa");
  //float pressure_pascal=pressure_event.pressure/1000 - 0.90883;
  Serial.println();

  array3[1] = temp_event.temperature;
  delay(1000);

  delay(500);
  wdt_reset();
}

void sendEvent()
{

  //Converting float value to char
  //The format (float, bytes, numbers of numbers after the decimal, char variable)
  dtostrf(co21, 4, 1, co21s);
  Wire.write(co21s); // appx 8 bytes
  Wire.write(",");

  dtostrf(co2temp1, 8, 4, co2temp1s);
  Wire.write(co2temp1s); // appx 8 bytes
  Wire.write(",");

  dtostrf(co2hum1, 7, 4, co2hum1s);
  Wire.write(co2hum1s); // appx 8
  Wire.write(",");

  dtostrf(pressure1, 6, 2, pressure1s);
  Wire.write(pressure1s); // appx 8
  Wire.write(",");

  dtostrf(loadvoltage1, 6, 4, loadvoltage1s);
  Wire.write(loadvoltage1s); // appx 8
  Wire.write(",");

  dtostrf(current1, 6, 4, current1s);
  Wire.write(current1s); // appx 8


  Wire.write("\n");

delay(1000);

}

Slave-2(UNO)


#include<Wire.h>
#include <avr/wdt.h>


//**************************************************** SCD30 **************************************************

#include "SparkFun_SCD30_Arduino_Library.h" //Click here to get the library: http://librarymanager/All#SparkFun_SCD30
SCD30 airSensor;

//************************************** BMP280 ***************************************

#include <Adafruit_BMP280.h>
Adafruit_BMP280 bmp; // use I2C interface
Adafruit_Sensor *bmp_temp = bmp.getTemperatureSensor();
Adafruit_Sensor *bmp_pressure = bmp.getPressureSensor();
float array3[1];

//********************************** INA219 ********************************************

#include <Adafruit_INA219.h>
Adafruit_INA219 ina219;
float shuntvoltage = 0;
float busvoltage = 0;

float power_mW = 0;

float array1[3];

//******************************************************************************************

float co22 = 0;
float co2hum2 = 0;
float co2temp2 = 0;
float pressure2 = 0;
float loadvoltage2 = 0;
float current2 = 0;

char co22s[4];
char co2temp2s[8];
char co2hum2s[7];
char pressure2s[6];
char loadvoltage2s[6];
char current2s[6];


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

  for (int i = 5; i > 0; i--) {
    Serial.print(i);
    delay(1000); // I sometimes need a few seconds to restart the serial console.
    wdt_enable(WDTO_4S);
  }


  Wire.begin(8);  ////UNO-1/Slave-1 Address
  Wire.onRequest(sendEvent);

  SensorInit(); // Initialize the displays
  
}

void SensorInit() {

   Serial.println("SCD30 Example");
  Wire.begin();


  if (airSensor.begin() == false)
  {
    Serial.println("Air sensor not detected. Please check wiring. Freezing...");
    while (1)
      ;
  }

  //************************************************************************************

   ina219.begin();
  ina219.setCalibration_16V_400mA(); // set measurement range to 16V, 400mA

  //************************************************************************************

   Serial.println(F("BMP280 Sensor event test"));

  if (!bmp.begin(0x76)) {
    Serial.println(F("Could not find a valid BMP280 sensor, check wiring!"));
    delay(10);
  }


  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,     /* Operating Mode. */
                  Adafruit_BMP280::SAMPLING_X2,     /* Temp. oversampling */
                  Adafruit_BMP280::SAMPLING_X16,    /* Pressure oversampling */
                  Adafruit_BMP280::FILTER_X16,      /* Filtering. */
                  Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */

  bmp_temp->printSensorDetails();

}


void loop()
{

if (airSensor.dataAvailable())
  {
    Serial.print("co22(ppm):");
    Serial.print(airSensor.getCO2());
    co22 = airSensor.getCO2();


    Serial.print(" temp2(C):");
    Serial.print(airSensor.getTemperature(), 1);
    co2temp2 = airSensor.getTemperature();


    Serial.print(" humidity2(%):");
    Serial.print(airSensor.getHumidity(), 1);
    co2hum2 = airSensor.getHumidity();
    Serial.println();
    Serial.println();

    Serial.println();
    Serial.print(" Pre-stream data");
    Serial.println();
    Serial.print(co22);
    Serial.println();
    Serial.print(co2temp2);
    Serial.println();
    Serial.print(co2hum2);
    Serial.println();

  }

  //****************************************************************************************

  
shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current2 = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage2 = busvoltage + (shuntvoltage / 1000);

  Serial.println();
  Serial.println();
  Serial.print("Load Voltage 2:  "); Serial.print(loadvoltage2); Serial.println(" V");
  Serial.print("Current 2:       "); Serial.print(current2); Serial.println(" mA");
  Serial.println("");
  Serial.println();
  Serial.println();
  array1[0] = busvoltage;
  array1[1] = shuntvoltage;
  array1[2] = loadvoltage2;
  array1[3] = current2;

//***************************************************************************************

sensors_event_t temp_event, pressure_event;
  bmp_temp->getEvent(&temp_event);
  bmp_pressure->getEvent(&pressure_event);

  Serial.println();
  Serial.println();
  Serial.print(F("Temperature 2 = "));
  Serial.print(temp_event.temperature);
  Serial.println(" *C");
  //
  Serial.println();
  Serial.print(F("Pressure 2 = "));
  Serial.print(pressure_event.pressure);
  Serial.println(" hPa");
  //float pressure_pascal=pressure_event.pressure/1000 - 0.90883;
  Serial.println();

  array3[1] = temp_event.temperature;
  delay(1000);

    
  delay(500);
  wdt_reset();
}

void sendEvent()
{
    
//Converting float value to char
//The format (float, bytes, numbers of numbers after the decimal, char variable)
     dtostrf(co22, 4, 1, co22s);
  Wire.write(co22s); // appx 8 bytes
  Wire.write(",");
  
    dtostrf(co2temp2, 8, 4, co2temp2s);
  Wire.write(co2temp2s); // appx 8 bytes
  Wire.write(",");

  dtostrf(co2hum2, 7, 4, co2hum2s);
  Wire.write(co2hum2s); // appx 8
  Wire.write(",");

  dtostrf(pressure2, 6, 2, pressure2s);
  Wire.write(pressure2s); // appx 8
  Wire.write(",");

  dtostrf(loadvoltage2, 6, 4, loadvoltage2s);
  Wire.write(loadvoltage2s); // appx 8
  Wire.write(",");

  dtostrf(current2, 6, 4, current2s);
  Wire.write(current2s); // appx 8
  


  delay(1000);
  
    Wire.write("\n");

  
}

I have another question regarding this setup, currently I am using 24.7k ohms Pull-up resistors. I will be adding more slaves (total 6 slaves - UNO's) to the Master-NodeMCU. Is the pull-up resistance value enough for all the 6 slaves? Each slave will have the similar i2c sensors connected.

Any help regarding this will be much appreciated.

Thank you in advance.

Topic		Replies	Views
I2C Master-Slave with NodeMCU and Arduino UNO Networking, Protocols, and Devices	5	1214	December 18, 2021
NodeMCU <-> i2c <-> NodeMCU Microcontroladores	13	930	October 24, 2021
Having doubt in I2C Programming	42	4437	May 5, 2021
I2C Protocol - Wire library / Can one slave act as writer and sender to Master? Networking, Protocols, and Devices	10	2891	May 6, 2021
help understanding I2c and arduino Syntax & Programs	22	9953	May 6, 2021

NodeMCU - Master and UNO - Slaves (I2C communication)

Related topics