Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)

User avatar
By Vishnu Gvv
#78164 Hello,
I have ESP 01 module, and it is connected with ARDUINO UNO. I have wired my ESP to Arduino as below
ESP - Arduino
VCC - 3.3 V
CH-PD - 3.3 V
TXD - digital pin 2
RXD - digital pin 3

and the program used here is

#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() {

//You may need to uncomment this block for the first run:
// ESP8266.begin(115200); // Change this to the factory baudrate used by ESP8266
// delay(1000);
// Serial.println("Setting BAUDRATE to 9600");
// ESP8266.println("AT+IPR=9600");


bool okReceived = false;

void loop() {

if (Serial.available() > 0)
String command = Serial.readStringUntil('\n');
Serial.println("Command Sent: " + command);

int responseCounter = 0;
if (ESP8266.available() > 0)
while (ESP8266.available() > 0)
if (responseCounter == 0)
Serial.println("Response Received:");

String response = ESP8266.readStringUntil('\n');


The module worked fine for the first time, and it has received the AT commands and responded back. When I powered off and again powered on the ESP module it seems not responding to AT commands and blue and red LEDs are constantly ON.
I kindly request the reader to help me with this issue, Thanks in advance
User avatar
By QuickFix
#78211 Looks like you've blown up your ESP. :(

Please note that the ESP works on 3.3V only (this includes both VCC as GPIO): it's not, I repeat not 5V tolerant.
An Arduino works with 5V levels and will eventually fry your ESP when you directly connect Arduino I/O pins to the I/O pins of the ESP without level conversion (even a simple voltage divider might suffice).

Please note this thread from a couple of days ago, of someone with a similar problem. :idea:

As another tip (it's also in my signature for a reason): when you're new to the ESP, first get yourself a development board; it will make your life so much easier and a complete board is equally cheap as a separate ESP-module.

Also the ESP8266 is a magnificent chip which is (at a lot of points) more powerful than an Arduino; most applications can be made with only an ESP without the use of an Arduino at all.
Since communication over AT is cumbersome not having to interface two microcontrollers is a big plus as well.

And the best part is: you can also write code for the ESP with the Arduino IDE and ESP-core. :idea:
User avatar
By Vishnu Gvv
#78285 Hi Quick Fix,
Many thanks for your reply. I tried as you suggested with a new ESP module and voltage divider circuit as shown below, instead of 0 and 1 pins in the Arduino I connected them to 10 and 11 pins as my code initiate a serial port through 10 and 11 pins. Even for this connections also the module worked for the first time and when I powered off and again powered on, the module stops responding to AT commands. I found in some articles that ESP module will have boot modes (UART and Flash boot) depending on GPIO pin configurations. I haven't used any of these GPIOs in my circuit. Does this affect the module? If you have any working model, can you please share the connection diagram of the model.

As you suggested, I can use the development board but I need to integrate the ESP with FPGA board. So
I want to test the ESP before going to FPGA implementation.

Thanks in advance, please share if you have any working model circuit diagram.