[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 with some terminal software indicated a checksum error.
Assuming the board was dead, [Pete] grabbed another — and suffered the same problem. The WEMOS boards wouldn’t program, but other boards had no issues. Sensing that something may be amiss, further research was in order. A forum post turned up discussing different programming modes for the ESP8266.
It turns out that there are different types of flash used …read more http://pje.fyi/PrkR6P