In ordrer to install all of esp-open-rtos toolchain and and blinky code example I've approximatively followed this protocol here at https://www.penninkhof.com/2015/03/esp8266-open-sdk/#comment-698 When flashing with esptool.py it works very well with an ESP-12E but not with the same board and an ESP-12F instead. Additionnal infos: I've the same problem by using eclipse. (I used both of Ubuntu and Debian, it didn't change anything)