[Solved]Need help to send data via Rx/Tx from ESP8266 ESP01 to Arduino Nano

[mc_pedro]

Hello,

I am unsuccessfully trying to send specific data (temperature), from an ESP8266 ESP-01S WLAN WiFi Modul to an Arduino Nano using Rx/Tx pins on both ends. The ESP is separately supplied with 3.3V. Connection is the folloing;
Rx/Tx Tx/Rx

Here is the code I use for the sender (= ESP8266 ESP01):

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>  // http web access library
#include <ArduinoJson.h>        // JSON decoding library
#include <SoftwareSerial.h>
#include <TimeLib.h>

SoftwareSerial toUno(3, 1); //Rx, Tx partie NEW
 byte pinState = 0;
 
const char *ssid     = "xxx";
const char *password = "xxx-xxxx";
 
void setup() {

 toUno.begin(9600); //partie NEW
  Serial.begin(115200);
 
  delay(500);
  Serial.print("Connecting.");
 
  WiFi.begin(ssid, password);   // access Wi-FI point
 
  while ( WiFi.status() != WL_CONNECTED ) {
    delay(500);
    Serial.print(".");
  }
  
  Serial.println("connected\r\n");

internet();

toUno.print("From the ESP8266 OLAA"); //partie NEW
 
}
 
void loop() 
{
  internet();
  
  
  }

void internet()
{
 
  if (WiFi.status() == WL_CONNECTED) { //Check WiFi connection status
 
    HTTPClient http;  //Declare an object of class HTTPClient
 
    // specify request destination
    http.begin("http://api.openweathermap.org/data/2.5/weather?q=Bt,pt&APPID=8b996a0dd66af5a4ada85678e81b013");
 
    int httpCode = http.GET();  // send the request
 
    if (httpCode > 0) { // check the returning code
 
      String payload = http.getString();   //Get the request response payload
 
    DynamicJsonBuffer jsonBuffer(512);
 
      // Parse JSON object
      JsonObject& root = jsonBuffer.parseObject(payload);
      if (!root.success()) {
        Serial.println(F("Parsing failed!"));
        return;
      }
 
      float temp = (float)(root["main"]["temp"]) - 273.15;        // get temperature
      int   humidity = root["main"]["humidity"];                  // get humidity
      float pressure = (float)(root["main"]["pressure"]) / 1000;  // get pressure
      float wind_speed = root["wind"]["speed"];                   // get wind speed
      int  wind_degree = root["wind"]["deg"];                     // get wind degree
 
      // print data
      Serial.printf("Temperature = %.2f°C\r\n", temp);
      Serial.printf("Humidity    = %d %%\r\n", humidity);
      Serial.printf("Pressure    = %.3f bar\r\n", pressure);
      Serial.printf("Wind speed  = %.1f m/s\r\n", wind_speed);
      Serial.printf("Wind degree = %d°\r\n\r\n", wind_degree);

toUno.write(toUno.read()); //partie NEW
delay(2000); //partie NEW

 
    http.end();   //Close connection
 
    }    }  
 
 delay(60000);   // wait 1 minute
 }

My questions:

1. How do I tell ESP01 to send the data through the TX pin (Pin 1) to the Arduino? I use SoftwareSerial toUno(3, 1);
   but it seems not to work.

2. How do I specify what data is to send, I only want to send temperature.

3. Now, on the Arduino Nano, how do I tell Arduino to read the data on its Rx port coming from ESP and to print it ( here the temperature) in a Led matrix?

Thanks in advance for all information

[gcjr]

before trying temperature, i would just try to send a string

if the esp is at 3.3V and the arduino is at 5V, won't you need something so that they transmit data at a voltage both can receive?

[mc_pedro]

Thank you for the advice. It looks complicated to set a common voltage between both modules.

[gcjr]

rs-485 interface chips make work because they use a balance signal (no ground)

[RayLivingston]

Level shifters are not necessary. You can simply put 2K series resistors on the Rx and Tx lines between the two chips. That will limit the current to a safe level for the ESP chip.

[mc_pedro]

Eureka!, but it is still not perfect.
I followed the recommendation to place a 2k resistance on each Rx/Tx connection. Finally I also connected the GND-cable coming from the 3.3V power supply to the Arduino GND pin, and it worked.
It’s not perfect, because the data coming from the ESP is incomplete and corrupted:

Temperature = 1.45°C
Humidity    = 93 %
Pressure    = 1.015 bar
Wind n=⸮T
emperature = 1.45°C
Humidity    = 93 %
Pressure    = 1.015 bar
Winp4

g6

Could it be that to much data is trying to flow through the Tx port at the same time? I tried to slow the flow by usind delay(20) after each value in the ESP code, but it did not help.

Thanks in advance for all suggestion to solve this.

Update: it is solved, I had to lower the BAUD to 9600 on ESP.