Cannot flash / run sketches on nodemcu devkit without connecting pin EN to 3V3

Development Tools IDE 1.x
1

Hi community,

I try to flash two old nodemcu devkit 0.9 boards with simple sketches.

After connecting them via USB to my Win10-Laptop, the serial device appears in the device manager and I can select the port (COM3) in Arduino IDE. When trying to flash the blink example sketch I receive these (well-known) error messages:

warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed

I tried every hint I found on the net about this issue (change usb port/cable, baud rate, check usb drivers etc.) but couldn't get it to work. The only thing that works is receiving board information via the IDE, so communication doesn't seem to be totally broken at least.

When connecting to the board via Putty I am not able to send any AT commands. Maybe that sounds like the board has any hardware failure, but I have the same situation with two of them... One of them was even brand new and originally boxed. I think there must be something else that I've overseen.

By accident I found out that the boards work without any issue when connecting pin "EN" to 3V3. I can flash them and run any sketches. When I remove the pin connection, nothing works anymore. Not even the sketch is runnung...

Does anyone have any idea? I really appreciate any help!

Thanks in advance,
Thomas

2

"espcomm_sync failed" Are typically a com port setting error.

Baud rates, line feeds, terminating characters could all be cause for that but quite often the more common issue is confusing TX and RX.

Normally TX goes to RX and RX to TX between two devices ( Chinese printing errors on boards excluded :wink: )
IIRC there was also an issue with early versions of nodeMCU's but I cannot remember exactly what it was and if it would affect your problem.
Seem to recall a firmware upgrade was recommended ?

3

EN needs to be high, otherwise the esp is in powerdown mode. Sounds right to me. Maybe the older versions of the board didnt do this for you?

4

Thanks for your answers!

Everythings is really strange... I found a third board in my box of arduino stuff which also was originally boxed. That one must be from the same order when I bought them two or three years ago. This board is working without any problems and without connection the two pins!

I don't know what's the difference between these boards. I think I have to keep in mind that two of them needs the pins to be conencted to work.