How to fetch multiple data from NodeMCU to Arduino Uno

Dear guys, I am currently writing codes on two-way communication between Arduino Uno and Node MCU. I was able to send multiple dataS from Arduino Uno to NodeMCU. However, I have some trouble fetching multiple data from NodeMcu back to Arduino Uno. I have tried out some code myself but it not working as I expected. The connection between the Arduino Uno and NodeMCU is as below. Can you show me how to pass ( A= 128 and B=456) from NodeMCU to the Arduino Uno? I really need some helps in fetching data from NodeMCU to Arduino Uno. Really appreciate it if you can help me out here.

Arduino Uno Code

const int GSR=A0;
int sensorValue=0;
int gsr_average=0;
int muscle=0;
char c; 
String dataIn;                      

void setup(){
Serial.begin(9600);              //hardware serial communicate with PC  

void loop(){
  long sum=0;
  for(int i=0;i<10;i++)           //Average the 10 measurements to remove the glitch
      sum += sensorValue;
   gsr_average = sum/10;
   muscle = 10;
   Serial.print(gsr_average);         Serial.print("A");
   Serial.print(muscle);              Serial.print("B");
   //reset variable

NodeMCU code

#include <SoftwareSerial.h>
SoftwareSerial DataSerial(D6, D7);        //D6=12, D7=13

char c;
String dataIn;
int8_t indexOfA, indexOfB, indexOfC;
String GSR;                              
String Muscle; 
int ReturnData1 = 888;
int ReturnData2 = 999;

void setup() {
Serial.begin(9600);                      // Open serial communications and wait for port to open:
DataSerial.begin(9600);                  //software serial communicate with NodeMCU

void loop() { 
    while(DataSerial.available()>0)       //read data serial
    //test data
    else       {dataIn+=c;}


        //Show all the data in serial monitor
        Serial.println("GSR = " + GSR);
        Serial.println("Muscle = " + Muscle);
        //reset variable

void Parse_the_Data()
  indexOfA = dataIn.indexOf("A");
  indexOfB = dataIn.indexOf("B");
  GSR = dataIn.substring (0, indexOfA);
  Muscle = dataIn.substring(indexOfA+1, indexOfB);

Hi @copernicus_yew

Post repeated?

RV mineirin

You had better make sure of your serial connections.

  1. If you have Rx connected to Rx, so you can't expect to receive anything either way.
  2. NodeMCU is strictly 3.3v

NodeMCU and Uno don't play too well together anyway, and you would be better off retiring the latter and going alone with the former. If that other thing is an analogue device, I understand you can now get a NodeMCU with ESP32, which has an analogue pin.

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