4Pcs ESP8266 Serial WiFi Module ESP-01 Updated Wireless Transceiver Board 3.3V for Arduino

These things work really well, especially considering their size. They use serial to connect to your Arduino or whatever, and use an extended AT command set to configure it, connect to WiFi and send/receive data. They also support AP mode so would be ideal for configuring your WiFi settings by first connecting your laptop/phone/etc to your project's own WiFi connection.If you're using this with the Arduino IDE there's a great library available on GitHub - search for ITEADLIB_Arduino_WeeESP8266It's not breadboard friendly, but that's easily solved if you buy the adaptor, make one, or use Dupont wires.

If you know what your doing with these, they are fun. Every single one I got from this packaged has worked perfectly

The internet is littered with issues people have had with these modules. In my case I finally figured out that after grounding GPIO0 during a board reset (to get into software download mode) and leaving the module alone for 15 seconds or so, it was possible to upload code without the "timed out waiting for packet header" error message. The "Blink" code that supports these erroneously says the inbuilt LED (identified as "LED_BUILTIN") is on pin 2. It's actually on pin 1, so you have modify the code to run the test program. Finally, the upload would not work at default 115,200 baud rate, but would upload at 74,880 baud, which you can set in AT mode. To make the code run, you then have to reset this module, which none of the advice I read tells you. It's a great little module, but if you are unlucky you may spend days figuring how to make it work.

These things are so ridiculously addicting it’s insane. Extremely versatile and useful beyond any review I can write could offer. I have them all ove my house running small sensors wired up to GPIO2. My only gripe is the red power light. Had to break it off the board and it would be nice to use the deep sleep function but having trouble wiring GPIO 16 to rst. But I love them. Next time I may order ones that have access to more ports but for now, and real small jobs, they’re great!

These are great little devices to set up home automation or IoT. Very easy to get running if you have worked with Arduinos in the past, although you need to be able to program with either a Uno set up as a pass thru or an FTDI cable. Lots of info out there to help. I used two of these to interface with my two garage doors. Toughest part was getting one of the GPIO pins to act as an input for the door sensor. After that was done, piece of cake.

Was excited to get these, but should have noticed the fine print. Not surprisingly, all 4 units are dead and unresponsive. despite using known working programmers that work fine on other ESP01s.Maybe I just got bad luck, but all other sellers stand behind their sales.

I purchased them to use as a Wifi accessory for my Arduino. Much to my surprise, I was able to fit the entire project on the ESP8266, no Arduino required. These things are unbelievably versatile, and an outstanding value.

Arrived quick, and were exactly what they were supposed to be. Was able to program and use right away. Be aware that you’ll need a 3.3v power supply and cannot be used directly with a 5v Arduino. Had to add a level shifter to my project (interfacing with an Arduino mega) to communicate.

Worked perfectly. Good speeds and connection.