I bought a WRL-13678 wifi module, but when I connect it to a 3.3V power source, the blue LED flashes once, then nothing happens.

I tried powering it from a 3.3V breadboard power supply (connected to a 9V DC adapter). The same happens if I connect it to my Arduino 3.3V rail.

I checked the Arduino serial monitor and nothing is coming over the wire.

Is the module DOA, did I fry it somehow, or am I doing something else wrong?


It turns out that newer variations of the module don't have a red LED, to limit power consumption, so the single blue flash when it powered on, was expected behavior

I got it to work by:

  • Loading an empty program into the Arduino UNO
  • connecting TX on the Arduino to TX on the ESP8266, and RX to RX. I build a voltage divider circuit to drop the RX from 5V on the Arduino to 3.3V on the WRL-1368.
  • Connecting 3.3V to VCC and "Enable" on the ESP8266.
  • Connecting ground to the ESP8266 and to the reset pin on the Aruduino. I let the reset pin, and other 2 pins on the ESP8266 float.

After this, I was able to issue AT commands.

I used a combination of these two tutorials:

https://www.geekstips.com/esp8266-arduino-tutorial-iot-code-example/ http://www.teomaragakis.com/hardware/electronics/how-to-connect-an-esp8266-to-an-arduino-uno/

EDIT: Based on Chris Stratton’s comment below, I’lll be reintroducing the voltage divider.

  • 2
    \$\begingroup\$ Where you say chip, you actually mean module. Omitting the voltage divider may be out of spec and a bad idea; it's hard to know because it's also possible that the 5v ATmega is disabled and the unspecified USB-serial solution is driving the lines at 3v3 anyway. If this is an actual UNO, what you are doing is a serious mistake as there the lines are at 5v. \$\endgroup\$ – Chris Stratton Jul 22 at 13:50
  • \$\begingroup\$ @ChrisStratton Following your comment, I reintroduced the voltage divider to drop the RX signal to 3.3V. \$\endgroup\$ – NMrt Jul 24 at 2:00
  • \$\begingroup\$ One of the links above suggested the need to upload an empty sketch to the Uno. This wasn't necessary. Also, the carriage returns were both NL+CR and the baud rate was 115200. The module seemed to work after power was removed and added back \$\endgroup\$ – NMrt Oct 18 at 14:25

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