Note: I post here since I did not find a better category.
I bought on Amazon these modules (2) sold by RUIZHI.
They works pretty well during the tests, powered by the USB with the Arduino IDE (2.2.1) running.
The problem comes when I detach the USB cable and then attach it again; the sketch does not start anymore. To have the sketch running I must re-upload it to the module.
After several test I reduce everything at the minimum: the Blink sketch with just the module connected to the USB cable, no other HW involved.
I see the power led On and the built-in led flashing a couple of times, then nothing else. The reset button has no effect.
At the end I found that the voltage at the RST pin is going High for a couple of seconds at the cable insertion and then it goes permanently Low.
The voltage at the 3.3V pin is around 3.1V (as my old tester says).
I do suspect that these modules are both defective, unless someone has a suggestion to try.
I can not power the module from an external PSU at the moment, but I will try it asap.
Since this is my last post for this year, I wish a positive 2024 to everybody
EDIT:
I do confirm that the problem is due to the two modules. I just received a similar board from AZ-Delivery and this does not show the odd behaviuor.
Furthermore, I finally was able to power the 2 original boards with an external +5V source and the probles disappeared; this address the malfunction to the USB power circuitry, I believe.