I have a problem with my Arduino Nano ATmega328 and my ESP8266 01 module. I have connected the ESP8266 on my Arduino board without FTDI.

I have made the following connection:

I an using a 5V Arduino Nano which of course is 5V. The ESP8266 is a 3.3V device and so I am using a voltage divider to bring the Arduino's 5V down to 3.3V. If you are using a 3.3V Arduino then you do not need the voltage divider.

  • The wiring is very similar to the FTDI.
  • Arduino pin 3 to voltage divider and then to ESP8266 RX
  • Arduino pin 2 to ESP8266 TX
  • Arduino GND to ESP8266 GND
  • Pull CH_PD HIGH with a 10K resistor to +3.3V
  • +3.3V to Vcc

You only need the voltage divider on the Arduino TX pin. The 5V Arduino will read 3.3V as HIGH so you can connect the ESP8266 TX pin directly to the Arduino RX pin.

The problem I had and I can't handle is that when I start up the Arduino Tx and Rx LEDs work continuously so I can't have access to my serial monitor of the Arduino IDE. So with that problem I can't send or receive any command to/from the IDE. Also when I try to upload my program to the Arduino board, I have to disconnect the ESP. If I don't I can't upload it.

Any ideas guys? I would be grateful

My circuit schematic

I also try to implement code with AltSoftSerial but I have library issues - my laptop does not recognize it (I downloaded it and I put it in the same folder with my code).

  #include <SoftwareSerial.h>

    SoftwareSerial ESPserial(2, 3); // RX | TX
    void setup() 
    {    Serial.begin(9600);     // communication with the host         computer

     // Start the software serial for communication with the ESP8266

     Serial.println("Remember to to set Both NL & CR in the serial monitor.");

     void loop() 
      // listen for communication from the ESP8266 and then write it to the serial monitor
       if ( ESPserial.available() )   {  Serial.write( ESPserial.read();}  / / listen for user input and send it to the ESP8266
      if ( Serial.available() )       {  ESPserial.write( Serial.read()  );  }}
  • Well, what did you expect? It seems you're using the same serial port for the PC and the ESP-01. Isnt SoftwareSerial a built-in library? Mar 20, 2016 at 14:34
  • Yes. Is there anyway to resovle this? I was able to found some solutions using an extra software serial but nothing happened. I am still unable to resolve this. Mar 20, 2016 at 16:07
  • Post your code. Mar 20, 2016 at 16:17
  • i have tried different codes but the basic one is the one below : Mar 20, 2016 at 17:02
  • You say the TX and RX leds onboard blink whenever you send stuff from the serial monitor? Did u set the monitor to "Both NL & CR"? How are u powering the ESP? Mar 20, 2016 at 19:15

1 Answer 1


Arduino Nano has its tx-rx serial port shared with the FTDI chip used by downloading and serial console. See https://www.arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf This means that if you drive these pins from ESP, it will flash leds, and all communication on these pins will interfere with serial monitor and board programming as well.

You may:

  • disconnect ESP during program downloading
  • pick a different board, which has a separate hardware serial port, such as Arduino Micro, Leonardo, or any Pololu A-star 32u4 boards, this way you have a dedicated serial port to control your ESP
  • wire the tx-rx of ESP to two other pins of your Arduino micro, and use a software serial library to bit-bang serial communication. (Note that serial receiving in software mode may require clever programming - since while your code does something else it can not receive anything).
  • Basically I ve connected my esp8266 to an ftdi 3.3V logic and it helped my resolve my problems i had. I also use a command to change my esp baudrate to 9600 from 115200. Then i connect my esp back to arduino nano and everything works fine :) ( I think ftdi is the most easy way to get started with an esp module. ) May 19, 2016 at 8:50

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