ESP8266 Community Forum

Can anyone advise? I have three identical NodeMCU ESP8266 boards and known good compiled code that has successfully uploaded and run on all three. On two of these boards a subsequent plug-in to a USB port, followed by an upload results in: esptool.py v3.0 A fatal esptool.py error occurred: Failed to connect to ESP8266. Timeout waiting for packet header. It appears the the boards have just 'died' .... the only possible way I could have damaged them is plugging them in. Googling I see that others claim to have fixed an identical problem by downgrading the esp8266 drivers, but I can't fathom how to attempt this. Has anyone seen or fixed this issue before please?

Hi - please ... someone help me out here! I've now partially solved this problem. I buzzed out GPIO 0 (pin D3 and GND) on my NodeMCU. When I depressed the FLASH button, NO circuit was made i.e. the FLASH button does NOT ground GPIO 0. So, I did this 'manually' using bread-board wire and ... lo and behold, on my laptop, I could upload code just fine to all three of these previously 'not-working' NodeMCUs.
Spookily however, I still got the time-out error when attempting the same operations on my desktop PC ... a desktop PC that was previously uploading to two of these MCUs just fine. That is before I uploaded some code to an Arduino UNO and subsequently tried uploading the NodeMCUs again. I'm delighted that the NodeMCUs are all functional, but keen to bottom out how this time-out is caused!

Is this embarrassing or terrific? With much sweat I have now fixed this myself. On the desktop I opened Device Manager to inspect the COM ports. Two devices were reported as allocated to port COM3 - Communications Port (COM3) and USB-SERIAL CH340 (COM3). This was the cause of communication failing to the Node MCU. By opening these, going to Port Settings, then Advanced, I was able to change and thus separate the port allocations. The Arduino IDE did not automatically reflect this change; I had to close the IDE and restart it, following which both ports showed up under Tools. Selecting the port allocated to CH340 enabled me to load the code.

Remove all your "Unused" (hidden) COM ports and it should work again; this is a known problem with esptool.py as it can't handle COM-port numbers with double digits (i.e. > 9):

• Physically remove all your USB -> UART convertors (= all your NodeMCU's) from your PC
• Press Windows start button
• Type and open "Device manager"
• Check the "Show hidden devices" option under "View"
• In the tree open up the "Ports (COM & LPT)" node
• Remove all COM-ports; if you have "Real" COM-ports on board your PC (often COM1/COM2), you can leave them as-is
• Plug in your NodeMCU's one by one: they should be detected again and given a COM-port below 10
• From now on, everything should work as expected

Tip: try to always use the same USB port on your computer to connect a dev-board to: this should (somewhat) limit the number of COM-ports it assigns to your boards.