esptool.py erase_flash command does seem to correctly erase the flash, since it then starts showing: rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT) flash read err, 1000 ets_main.c 371 ets Jun 8 2016 00:22:57 But uploading the minimal "Hello World" sketch keeps showing the same behavior...