I want to get data from ESP to my Arduino. I added firmware v2 to my ESP and it works correctly in my serial USB to TTL and shows the JSON data that I send to it.

But when I connect to my Uno serial it shows some unknown chars.

#include <SoftwareSerial.h> //Including the software serial library
#define DEBUG true
SoftwareSerial esp8266(2, 3); // This will make the Arduino pin 2 as the RX pin and Arduino pin 3 as the TX. Software UART
/* So you have to connect the TX of the esp8266 to the pin 2 of the Arduino and the TX of the esp8266 to the pin 3 of the Arduino. This means that you need to connect the TX line from the esp to the Arduino's pin 2 */

void setup() {
  Serial.begin(115200); // Setting the baudrate to 9600
  esp8266.begin(115200); // Set it according to your esp’s baudrate. Different esp’s have different baud rates.
  pinMode(11, OUTPUT); // Setting the pin 11 as the output pin.
  digitalWrite(11, LOW); // Making it low.
  pinMode(12, OUTPUT); // Setting the pin 12 as the output pin..
  digitalWrite(12, LOW); // Making pin 12 low.
  pinMode(13, OUTPUT); // Setting the pin 13 as the output pin.
  digitalWrite(13, LOW); // Making pin 13 low.
  sendData("AT+RST\r\n", 2000, DEBUG); //This command will reset module to default
  sendData("AT+CWMODE=2\r\n", 1000, DEBUG); // This will configure the mode as access point
  sendData("AT+CIFSR\r\n", 1000, DEBUG); // This will get ip address and will show it
  sendData("AT+CIPMUX=1\r\n", 1000, DEBUG); // This will configure the ESP8266 for multiple connections
  sendData("AT+CIPSERVER=1,80\r\n", 1000, DEBUG); // This will set the server on port 80

void loop() {
  if (esp8266.available()) {
    // Checking that whether the esp8266 is sending a message or not (Software UART Data)
    while (esp8266.available()) {
      // Checking whether ESP8266 has received the data or not
      char c = esp8266.read(); // Read the next character.
      // Storing the response from the ESP8266

String sendData(String command, const int timeout, boolean debug) {
  // Function to send the data to the esp8266
  String response = "";
  esp8266.print(command); // Send the command to the ESP8266
  long int time = millis();
  while ((time + timeout) > millis()) {
    // ESP8266 will wait for some time for the data to receive
    while (esp8266.available()) {
      // Checking whether ESP8266 has received the data or not
      char c = esp8266.read(); // Read the next character.
      response += c; // Storing the response from the ESP8266
  if (debug) {
   // Printing the response of the ESP8266 on the serial monitor.
  return response;

Prints this for me:




+IPD,0,385:POST / HTTP/1.1
cache-control: no-cache
Postman-Token; 45494ff7-b3e1-400f-8afc-fcda26514705
Content,Type: application/jsonUser-Agent: PostmanRunthme/6.1.6
@ccept: */*Host:
accept-encoding: gzip, defl`te
content,length: 14Connection: keep-alive

My correct JSON is: {"name":"ali"}. But it shows incorrectly. And I set the mt serial library to #define _SS_MAX_RX_BUFF 1024.

How can I fix this?

My connection is:

my connection


i used AT+UART_DEF=9600,8,1,0,0 and it works correctly now


Software serial doesn't work reliably at 115200. You need to use a lower baud rate:

  1. Connect the ESP8266 back to your serial USB to TTL setup.
  2. Send the following command to reconfigure the ESP8266 to do AT communication at 9600 baud: AT+UART_DEF=9600,8,1,0,3
  3. Change line 9 of your sketch to esp8266.begin(9600);. This will cause the Uno to communicate with the ESP8266 at 9600 baud.
  4. Upload the revised sketch to your Uno and connect it back up to the ESP8266.
  • when i use this command AT+UART_DEF=9600,8,1,0,3 and i change to 9600 do not show any thing or command AT no response from esp why this happen Aug 13 '17 at 5:54

Try connecting arduino's TX and RX pins (0 and 1) with esp8266's RX and TX and see if it works. Upload a blank sketch. Whatever you type in serial box will be sent to esp. Instead of using voltage divider you should use logic level converters with LM2596.

  • i used pin 0 and 1 but nothing changed why some characters shows wrong
    – aliyousefian
    Aug 12 '17 at 16:57

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