struggling with similar issue.... nodemcu 1.0 (esp8266EX) - connected on com6, but back of board says connect at 9600. serial monitor at 9600 can display correct messages at boot.. no AT command response, but then when i upload some simple code i get the following: .... Features: WiFi Crystal is 26MHz MAC: ec:fa:bc:27:cc:12 Uploading stub... Running stub... Stub running... Configuring flash size... Traceback (most recent call last): File "C:\Users\jph1l\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.0.1/tools/", line 66, in <module> esptool.main(cmdline) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 3599, in main detect_flash_size(esp, args) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 2848, in detect_flash_size flash_id = esp.flash_id() File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 688, in flash_id return self.run_spiflash_command(SPIFLASH_RDID, b"", 24) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 948, in run_spiflash_command old_spi_usr = self.read_reg(SPI_USR_REG) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 562, in read_reg val, data = self.command(self.ESP_READ_REG, struct.pack('<I', addr)) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 386, in command p = File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 331, in read return next(self._slip_reader) File "C:/Users/jph1l/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.1/tools/esptool\", line 2636, in slip_reader raise FatalError("Timed out waiting for packet %s" % waiting_for) esptool.FatalError: Timed out waiting for packet header esptool.FatalError: Timed out waiting for packet header any ideas - change usb cable, ports, confirmed the com not used elsewhere... any ideas? FYI - the blue LED on the NodeMCU does flash once you start the upload.. flash a couple of times then stops. Pressing the FLASH and holding down before the upload command or once it tries to connect etc there is no difference.