NodeMCU - Master and UNO - Slaves (I2C communication)

Projects Programming
6

@kpuvvala
1. Make connection between NodeMCU and UNO-2 only as per Fig-1 of Post-3. Do not forget to install the I2C Bus pull-up resistors.

2. Upload the following sketch in NodeMCU.

#include <Wire.h>

void setup()
{
  Wire.begin(D4, D3); //SDA=D4, SCL=D3
  Serial.begin(9600);  // start serial for output
  //----------------------------------------------------------------
  Wire.beginTransmission(9);
  byte busStatus = Wire.endTransmission();
  if(buStatus !=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()
{
  Wire.requestFrom(9, 1);    // request  bytes from slave device #8
  byte y = Wire.read();
  Serial.print("Reading 1-byte from Slave-2: ");
  Serial.println(y, HEX);
  //------------------------
  delay(1000);
}

3. Upload the following sketch in UNO-2.

#include<Wire.h>

void setup()
{
  Serial.begin(9600);
  Wire.begin(9);  ////UNO-2/Slave-2 Address
  Wire.onRequest(sendEvent);
}

void loop()
{

}

void sendEvent()
{
  Wire.write(0x27);
}

4. Check that the Serial Monitor of NodeMCU shows: 27 at 1-sec interval.
5. Now Connect UNO-1/Slave-1 and check that both slaves are operational.