Arduino sending float numbers to NodeMCU (ESP8266)

Projects General Guidance
1

I want to send from an Arduino float data to NodeMCU (ESP8266), without lose the decimals.
The basic circuit is connected this way:

Arduino | NodeMCU

3 (Rx) | Tx

2 (Tx) | Rx

GND | GND

Vcc(usb) | Vcc(usb)

I'm receiving data in a float format but they do not have the decimal values. While if I try to transmit int values, this works with no errors.

Here's my code:

Arduino

#include<SoftwareSerial.h> //Included SoftwareSerial Library
//Started SoftwareSerial at RX and TX pin of ESP8266/NodeMCU
//arduino sending

//int a;
float f;

SoftwareSerial s(3,2);    //Rx, Tx

void setup() {
  //Serial S Begin at 9600 Baud
  //Serial.begin(9600);
  s.begin(9600);
}

void loop() {

  //a = 10+random(1,5);
  f = 1.5+random(1,5);

  //s.write(a);
  s.write(f);
  delay(1000);
  //Serial.println(f, 3);
  //Serial.println(a);
}

NodeMCU (ESP8266)

//int data; //Initialized variable to store recieved data
float data1;
//nodemcu receiving


void setup() {
  //Serial Begin at 9600 Baud 
  Serial.begin(9600);
}

void loop() {

  data1 = Serial.read();
  delay(1000);
  Serial.println(data1);
  
}

How can I solve this? Do you have similar simple example to show with SotwareSerial.h library? Thank You

2

Pleasr read this from Arduuino reference. Then You will know.

Serial.read()
Description
Reads incoming serial data.
Serial.read() inherits from the Stream utility class.
Syntax
Serial.read()
Parameters
Serial: serial port object. See the list of available serial ports for each board on the Serial main page.
Returns
The first byte of incoming serial data available (or -1 if no data is available). Data type: int.

3

Serial.read() returns a byte:

data1 = Serial.read() ;

but you want 4 bytes. A float is represented as 4 bytes.

4

I'm sorry but I'm not an expert. So I understood that with Serial.read I can only read 1byte, but my question remains, how can I send and read the float (4bytes)?
I do not have idea, i wouldn't had asked here.

5

You need to read 4 bytes, glue them together and do some kind if type casting, cheating the compiler to read those 4 bytes as a float. Easy to do in assembler but harder to make it pass the C-compiler.

6

You can use SerialTransfer.h to automatically packetize and parse your data for inter-Arduino communication without the headace (including floats!). The library is installable through the Arduino IDE and includes many examples.

Here are the library's features:

This library:

  • can be downloaded via the Arduino IDE's Libraries Manager (search "SerialTransfer.h")
  • works with "software-serial" libraries
  • is non blocking
  • uses packet delimiters
  • uses consistent overhead byte stuffing
  • uses CRC-8 (Polynomial 0x9B with lookup table)
  • allows the use of dynamically sized packets (packets can have payload lengths anywhere from 1 to 255 bytes)
  • can transfer bytes, ints, floats, and even structs!!

Example TX Arduino Sketch:

#include "SerialTransfer.h"

SerialTransfer myTransfer;

void setup()
{
  Serial.begin(115200);
  Serial1.begin(115200);
  myTransfer.begin(Serial1);
}

void loop()
{
  float myFloat = 5.2;
  myTransfer.txObj(myFloat, sizeof(myFloat));
  myTransfer.sendData(sizeof(myFloat));
  delay(100);
}

Example RX Arduino Sketch:

#include "SerialTransfer.h"

SerialTransfer myTransfer;

void setup()
{
  Serial.begin(115200);
  Serial1.begin(115200);
  myTransfer.begin(Serial1);
}

void loop()
{
  if(myTransfer.available())
  {
    float myFloat;
    
    Serial.print("New Data: ");
    myTransfer.rxObj(myFloat, sizeof(myFloat));
    Serial.println(myFloat);
  }
  else if(myTransfer.status < 0)
  {
    Serial.print("ERROR: ");
    Serial.println(myTransfer.status);
  }
}
7

Riemanndiy:
I'm sorry but I'm not an expert. So I understood that with Serial.read I can only read 1byte, but my question remains, how can I send and read the float (4bytes)?
I do not have idea, i wouldn't had asked here.

A simple answer might be to just send/receive the numeric value as a string of characters that represents the numeric value, then convert the string of characters back into the numeric value after it has been received.

8

Thank You so much @Power_Broker, stunning library! this works perfect, I would add a random component to the variable myFloat to simulate a sensor.

float myFloat = 5.2 + random(1,5);

I'm giving you a star on github

9

I am having issues sending data between Arduino and NodeMCU.

I am using the suggested "SerialTransfer.h" library. In the example sketch "softwareserial_rx/tx_multi_byte" a sruct with multiple fields is sent. When i try this script the char is transferred but the float is depicted as 0.00. When i add an additional integer the integer is also not received correctly. I tried sending only int or float or char and i works without any problem. I really dont understand what is happening since this library is mentioned in almost every post regarding serial communication between two devices and i cant get it to work properly. Would really appreciate some help. Since i am new to this Forum i am not sure if posting the used example code would be of any help in this scenario, if it does, please let me know.

10

anthero:
this library is mentioned in almost every post regarding serial communication between two devices

:wink:

anthero:
I am having issues sending data between Arduino and NodeMCU.

Please post all your sketches in tags. It's impossible to help without being able to see the code.