[Pete] was building a hot tub controller, using a WEMOS board based on the venerable ESP8266. After assembly, the board was plugged into USB and [Pete] hit the flash button. No dice. Investigation ...

The ESP-01 launched the ESP8266 revolution back in 2014, and while today you’re far more likely to see somebody use a later version of the chip in a Wemos or ... unusual pinout of the ESP ...