Some ESP32 development boards (read Best ESP32 boards) don’t switch into flashing/uploading mode automatically when uploading a new code with for example the “standard” Arduino IDE. This means that when you try to upload a new sketch to your ESP32 development board, the Arduino IDE fails to connect to your board, and you get the following error message:
In the Random Nerd Tutorial you find more detailed explained wy this happen. Also there a number of solutions are given that circumvent the problem, but unfortunately not with my board SBC-NodeMCU-ESP32 from Joy-It (www.joy-it.net).
Investigation of the ESP32-Wroom-32E module, used in the SBC-Nodemcu-ESP32 indicated that the enable pin was not made “high” by the intern pull-up resistor or by the IDE. The voltage on this pin roamed a bit around “0” volts or slightly higher. In any case, insufficient for “enable” the module for programming.
Because of solutions as previously described did not work, it was decided to lay the enable pin “hard” to the 3.3 volts and then program the module with the IDE, and surprisingly that worked wonderfully!!!
It also appeared that after re-programming in this way something apparently reset in the ESP32-module, so that a following programming no longer needed to keep the 3.3 volts at the ENable pin. The module works “normal” again.
I don’t know the real reason why the enable pin remains low and the module cannot be re-programmed. I think it is a program error in the sketch I used where the enable pin is “low” in unintentionally by program. The result of re-programming is, that re-program is blocked.