I am new to working with Arduino Uno and ESP8266.

Firstly I connected an ESP8266 to an Arduino Uno like so:

  • TX to TX,
  • RX to RX,
  • GND to GND,
  • VCC to 3.3V,
  • CH_PD to 3.3V and
  • adding RESET to GND on the Arduino Uno.

After completing the wire connection, I opened the Arduino IDE serial monitor, where it always shows symbols and text and I set baud rate 115200 and adjusted both NL and CR.

After all of that, when I send an AT command, then no response is shown.

  • using USB of Uno is a replacement for proper USBtoTTL adapter and it doesn't work with all Unos. And 3.3 V pin of Uno can't supply enough current for esp8266 WiFi operations – Juraj Jul 3 '18 at 13:08
  • i connected 5v power, blue led stay on. not send AT command. – Saif Ullah Saiful Jul 3 '18 at 13:51
  • 1
    if you feed 5 V to VCC of esp8266 you can destroy it – Juraj Jul 3 '18 at 14:11
  • Uno can only supply 150mA of current at 3.3V. You need a 3.3V supply for the ESP8266. Be sure to connect all the Gnds together. – CrossRoads Jul 3 '18 at 14:28
  • i have been changed 3.3v, but AT command not send, always blue led on. – Saif Ullah Saiful Jul 4 '18 at 3:12

TX is an output. RX is an input.

By connecting TX to TX and RX to RX you have connected an output to an output, and an input to an input.

You need to connect the TXs to the other RXs.

Also: see (NEWBIE) Sending AT Command from Arduino UNO to ESP8266 doesn't work

  • 2
    by doing so, he uses the USB converter of the Uno – Juraj Jul 3 '18 at 13:03
  • @Juraj Sorry, but I don’t see how connecting two outputs together can ever be a good idea. How does that “use the USB converter”? – John Burger Jul 3 '18 at 13:20
  • 1
    USB chip of Uno is to 328p connected RX to TX and TX to RX. the pins 0 and 1 of Uno are RX and TX of 328p. if you connect esp8266 RX to 0/RX of Uno, you connect it to TX of USB chip . and that enables the communication of the computer with the esp8266. 328p does nothing and must be silent – Juraj Jul 3 '18 at 13:31
  • @Juraj That works fine for the direction you stated (USB to both 328p and ESP8266). Unfortunately, the other, TX/TX connection is the problem. Even if the 328p is silent, it is still “forcing” a voltage on the TX pin, while the ESP8266 is too. This is not good! – John Burger Jul 3 '18 at 13:41
  • 1
    if you connect esp8266 TX to 1/TX of Uno, you connect it to RX of USB chip. and that enables the communication of the computer with the esp8266. 328p does nothing and must be silent – Juraj Jul 3 '18 at 14:08

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