I have a strange behavior, using ESP32 devkit v.1 boards. Everything works, I can upload blink sketch, serial works, led blinks. However, once I upload any sketch which is using the wifi.h (and utilizing it for example calling WiFi.mode(WIFI_STA);), upon upload, the board keeps resetting the serial connection, stays up for not more then 1 second, resets again, and so on. I could not debug the issue, since serial is unusable. Any ideas what is wrong? I did a fresh ArduinoIDE, ESP32 board manager install, etc. and normal sketches work flawlessly.

  • based on esp8266 experience. try to erase the flash with esptool.
    – Juraj
    Nov 1, 2018 at 18:12
  • Could be a power problem. WiFi needs a lot of power.
    – Majenko
    Nov 1, 2018 at 19:38
  • @Majenko, the devkit has USB connector. I assume Miro powers the board from USB.
    – Juraj
    Nov 1, 2018 at 19:47
  • Yes, but what from? An unpowered hub would be fatal...
    – Majenko
    Nov 1, 2018 at 20:30
  • Guys, Juraj was right, I had a too long usb cable, no idea that the power loss could be high enough not to run the esp. Sorry for an unnecesaary question. If anyone has reboots with wifi ON, try a shorter cable.. Nov 3, 2018 at 5:30

1 Answer 1


The USB cable was too long, and hence power loss.

Sorry, I figured it out a day after I asked this question.

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