Connecting ESP8266 to Arduino Uno

Question

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.
      Serial.print(c);
      // 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) {
    Serial.print(response);
   // Printing the response of the ESP8266 on the serial monitor.
  }
  return response;
}

Prints this for me:

???AR)?WS?TZ?eO?C?AJ+CIFSR
+CIFSR:APHP,"192.168.4.1"
+CIFSQ:APMAC,"62:01:94:22:96:7e"

OK
AZ??R????jC?u?H?AT+CIPSERVDR=1,80

OK
0,CONNECT

+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: 192.178.4.1
accept-encoding: gzip, defl`te
content,length: 14Connection: keep-alive
{"name":"`li"}0,CLOSED

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:

score 3 · Answer 1 · answered Aug 20 '17 at 14:59

3

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

answered Aug 20 '17 at 14:59

aliyousefian

181
4

score 2 · Answer 2 · answered Aug 13 '17 at 00:30

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

Connect the ESP8266 back to your serial USB to TTL setup.
Send the following command to reconfigure the ESP8266 to do AT communication at 9600 baud: AT+UART_DEF=9600,8,1,0,3
Change line 9 of your sketch to esp8266.begin(9600);. This will cause the Uno to communicate with the ESP8266 at 9600 baud.
Upload the revised sketch to your Uno and connect it back up to the ESP8266.

score 1 · Answer 3 · answered Aug 12 '17 at 12:03

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.

Connecting ESP8266 to Arduino Uno

3 Answers3