I am working on an esp8266 and I am connecting it with Arduino Uno. I have programmed the Arduino but when I write AT command on the serial monitor it doesn't show anything.The connections which i have made are:

tx uno - rx esp
rx uno - tx esp
gnd uno -gnd esp
vcc and ch_pd - 3.3v supply

I am using an external supply and not the 3.3v from the Arduino. I need help with this.

  • And how exactly do you think the ESP8266 is connected to the USB-UART bridge? Jul 6, 2015 at 7:12
  • It is connected via the connections which i have mentioned. Jul 6, 2015 at 7:25
  • No, it isn't. It is connected backwards. Jul 6, 2015 at 7:29
  • what do u mean by backwards? Jul 6, 2015 at 8:09
  • You have RX of the bridge connected to RX of the device, and the same with TX. Jul 6, 2015 at 12:37

2 Answers 2


Be careful, you could fry your ESP like that. You need to get the signal lines down to 3.3V, not the 5V used by the Arduino Uno. There are many ways to do this, from voltage dividers, to transistors, or you can use a 3.3v Arduino Pro Micro. I would also recommend starting out with just a 3.3v FTDI board, and interface that directly to the ESP to remove the Arduino and its code from the picture.

I would also make sure that your grounds on the external supply and the Arduino are tied together, or just power the ESP from the 3.3v out of the Arduino.

Other than that, double check your baud rate, some come shipped at 9600, some at 115200, and i'm sure that there are others out there too shipping at different baud rates.


Sorry if these are stupid questions but these are the things I would check.

  1. Why are you connecting to an Arduino, why not connect directly to the HOST and use a terminal emulator program?
  2. What ESP8266 are you using?
  3. Are you connecting the Vcc connector of the ESP8266 to 3.3v?
  4. I think you need to pull the RST pin high to enable normal running, is it high?

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