ESP8266/ESP201 WiFi module
ESP201 is a breadboard-friendly version of ESP8266 WiFi module. Two rows of pins are spaced with 900mils between them
thus they are leaving one empty pin row on each side of typical breadboard and four pin connector for UART.
For unknown reason someone decided to put side connectors descriptions on bottom side, making them not useful in typical use.
This particular module came with 25Q80 (8 Mbit) serial FLASH soldered.
ESP201 can use PCB antenna or external antenna (very basic antenna is included in set).
Type of used antenna has to be selected by resoldering 0 Ohm resistor next to UFL connector.
Apparently some (early?) modules may have UFL socket soldered incorrectly. Mine was fine, on the other hand goldpin connectors on the sides needed resoldering as they were soldered at wrong angle. Also, as with every other ESP201 intended to be used with breadboard UART connector needed replacing with right angle type.
For effortless switching between programming and normal mode schematic from this page still works, but GPIO15 needs to be connected to GND.