Send AT commands to ESP8266 from Arduino Uno via a SoftwareSerial port

Question

GOAL

From Arduino UNO, send AT commands to ESP8266 via a SoftwareSerial port and receive results.

CURRENT STATUS

I either send AT commands and get nothing back (wiring scheme 1) or I send AT commands and get garbage back (wiring scheme 2).

Using the Arduino as a pass through (as explained in the tutorial listed in the resources section), I can send AT commands. I have found that I can communicate with the ESP8266 at 115200 baud.

This is the results of running AT+GMR:

AT version:0.40.0.0(Aug  8 2015 14:45:58)
SDK version:1.3.0
Ai-Thinker Technology Co.,Ltd.
Build:1.3.0.2 Sep 11 2015 11:48:04

WIRING SCHEME 1

!! I have the green wire attached to pin 3 on the Arduino Uno and the yellow wire attached to pin 2; not 1 and 0 as the picture suggests !!

WIRING SCHEME 2

Same wiring as above, but I have RX and TX reversed. The green wire is attached to pin 2 and the yellow wire is attached to pin 3.

CODE

This is running on Arduino Uno

#include <SoftwareSerial.h>

SoftwareSerial esp8266(2, 3);

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.println("Started");

  // set the data rate for the SoftwareSerial port
  esp8266.begin(115200);
  esp8266.write("AT\r\n");
}

void loop() {
  if (esp8266.available()) {
    Serial.write(esp8266.read());
  }
  if (Serial.available()) {
    esp8266.write(Serial.read());
  }
}

RESULTS FROM RUNNING SKETCH

Wiring Scheme 1

Started

Wiring Scheme 2

Started
�����

I have tested the ESP8266 via the instructions listed in the tutorial in the Resources I've Used section below. The ESP8266 works just fine when sending it instructions via the Serial Prompt.

RESOURCES I'VE USED http://rancidbacon.com/files/kiwicon8/ESP8266_WiFi_Module_Quick_Start_Guide_v_1.0.4.pdf

QUESTION

Does anyone know if what I am trying to do is possible? And if it is, what am I doing wrong?

Answer 1

Does anyone know if what I am trying to do is possible?

Absolutely possible :)

And if it is, what am I doing wrong?

SoftwareSerial isn't capable of 115200 baud rate (despite "allowing" this as a setting). Some reports suggest as high as 57600 is workable, though in my experience 9600 is best for reliability. How to change the baud rate on the ESP8266 will depend on the firmware version. I've had success with AT+IPR=9600. You only need to run this command once (it's a persistent setting). I'd suggest, based on your description, that this is the most likely culprit that's causing the "garbage" output you describe.

A couple of other notes:

• The ESP8266 runs on 3v3, not 5v, so you shouldn't have it directly connected to the digital pins—you need to run through a logic level converter. Running 5v can fry your ESP8266.
• The Arduino's 3v3 output has insufficient current to support the ESP8266 reliably (50mA Arduino vs up to 300mA for the ESP8266 by some accounts)—try running the ESP8266 off a separate supply. It probably won't affect simple commands like AT but when you try to connect to a network etc. it may cause unexpected device resets.
• As noted by others, you need to send \r\n — so make sure your Serial window is set to send both (this is a drop-down in the serial window)

Answer 2

Well you may try this:

Start by uploading blink sketch to your Arduino then connect it to your ESP8266 like this: TX-TX and RX-RX.

Now open Serial Monitor and send AT command and see if it responds. If so then you can control it using your Arduino by wiring it back to TX-RX and RX-TX.

PS: Don't forget to set the line ending in the Serial Monitor to Newline or Carriage Return.

Use this code to connect to ESP8266:

#include <SoftwareSerial.h>

const byte rxPin = 2; // Wire this to Tx Pin of ESP8266
const byte txPin = 3; // Wire this to Rx Pin of ESP8266

// We'll use a software serial interface to connect to ESP8266
SoftwareSerial ESP8266 (rxPin, txPin);

void setup() {
  Serial.begin(115200);
  ESP8266.begin(115200); // Change this to the baudrate used by ESP8266
  delay(1000); // Let the module self-initialize
}

void loop() {
  Serial.println("Sending an AT command...");
  ESP8266.println("AT");
  delay(30);
  while (ESP8266.available()){
     String inData = ESP8266.readStringUntil('\n');
     Serial.println("Got reponse from ESP8266: " + inData);
  }  
}

Since the Hardware Serial interface will be busy when connected to Computer, then you have to use another Serial interface to communicate with your ESP8266. In this case, Software Serial comes handy.

Answer 3

Does anyone know if what I am trying to do is possible? It is possible, i've done it with 2 arduinos where one was simulating ESP8266 (waiting for ebay order).

And if it is, what am I doing wrong?

What you are doing is wrong on most levels, but i think you got most sorted out.

An idea is to implement this little fella: Logic level shifter it will save you many troubles later.

On your "WIRING SCHEME 1" you are using the arduino's Hardware serial port to talk directly to the device as if it was connected through a TTL cable or FTDI cable.

This means that the arduino device would in theory read from the hardware when talking too the ESP8266, if you have another arduino or a TTL cable, try and connect it to gate 2 and 3 on the "main" arduino and you should get a similar result as for your example result 2. Since you would that way proxy through the arduino. If not that would be a place to start debugging.

Beside that i could only recommend you in investing in either a TTL 3,3v or a logic level converter. When i got my cable everything worked out of the box.

Answer 4

I had lot of problems as well. In my case problems are almost solved by switching from SoftwareSerial to AltSoftSerial. It seemed that on the Uno the standard software serial library was not working for me. After switching I started to get results back for the first time. (I also used level shifting and external power supply for 3.3V)

---

And by almost solved I mean - I still get, from time to time, gibberish on the terminal. So even AltSoftSerial isn't a perfect solution. I was using the ESP-07 with a 115200 bps data rate.

Answer 5

We found that many of the problems with the ESP - Arduino Uno serial software integration had to do with incompatible baudrate. We created this short tutorial (including a Github library) which you are welcome to test and see if it solves these issues. http://www.instructables.com/id/Simple-ESP8266-Arduino-Uno-Software-Serial-Integra/

Answer 6

Here are a few tips when using ESP8266 Module.

1. Don't use software serial as it's unreliable especially at higher baud rates.

2. Always connect ESP module to computer and test all AT commands before interacing with Arduino to ensure that you are working in right direction

3. Make a power adaptor board to make ESP module compatible with Arduino 5v supply

Also check out this link for more details