Serial communication not working (NANO to WEMOS)

Projects Networking, Protocols, and Devices
1

Serial communication not working. Don't know why?

NANO:

#include <SoftwareSerial.h>

SoftwareSerial ArduinoNano(6,5); // RX, TX
String f;
void setup(){
   Serial.begin(9600);
   ArduinoNano.begin(9600);
}
void loop(){
  float i = (random(100) + 1);
  float j = (random(100) + 1);
  
  f = String('H')+String(i)+String('T')+String(j); 
  Serial.println(f);
  ArduinoNano.println(f);
  delay(2000);
}

WEMOS over 3v3 converter and RX (D6) to TX wemos ... AND TX (D5) to RX wemos is:

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

void loop()
{
  if (Serial.available())
  {

   String  readString="";
   while (Serial.available()) 
   {
     delay(2); 
     char c = Serial.read();  
     if (c >= 32)
      readString += c;
   }

  Serial.println(readString"); 
}
2

At least the Wemos code doesn't compile.

3

cevepe:
Serial communication not working. Don't know why?

Have you a common GND between the Nano and the Wemos?

Try sending a simple message to start with - such as "Hello world"

It is not a good idea to use the String (capital S) class on an Arduino as it can cause memory corruption in the small memory on an Arduino. This can happen after the program has been running perfectly for some time. Just use cstrings - char arrays terminated with '\0' (NULL).

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

The technique in the 3rd example will be the most reliable. It is what I use for Arduino to Arduino and Arduino to PC communication.

You can send data in a compatible format with code like this (or the equivalent in any other programming language)

Serial.print('<'); // start marker
Serial.print(value1);
Serial.print(','); // comma separator
Serial.print(value2);
Serial.println('>'); // end marker

...R