If you are looking to add some WiFi connectivity to your next project the HLK-RM04 Serial to WiFi Module might be just the thing if you want to go wireless. The $10 HLK-RM04Â module handles all of the WiFi overhead so your microcontroller project can simply send serial data to it using the TX and RX pins. RAYSHOBBY.NET has a great tutorial including code to get you started with this module.
Via: Dangerous Prototypes
“The chip (RT5350F) is a 360MHz MIPS core with built-in WiFi support. The module is quite powerful — at factory default settings it functions as a normal WiFi router. Now, in order to get it to talk to a microcontroller like Arduino, I need to use its Serial-to-WiFi capability. What is that? Well it means using the serial (TX/RX) interface to send and receive Ethernet buffers, and similarly using serial to send commands to the module and query or change its current status. This is quite convenient because first, it only takes two wires (TX/RX) of the microcontroller to talk to the module, second, it moves WiFI-related tasks to the module allowing the Arduino code to be very much light-weighted. “