ESP32 keeps rebooting in a boot loop

Where this problem appears

ESP32 development boards powered by USB or an external regulated supply.

Symptoms to confirm

• The serial monitor repeats the boot message.
• The board resets when Wi-Fi, a motor or a sensor starts.
• A new sketch uploads but never reaches the main loop.

Likely causes

• The USB cable or power supply drops voltage under load.
• A peripheral pulls too much current or disturbs a boot strapping pin.
• The sketch triggers a watchdog, exception or memory failure.
• Flash contents or board settings do not match the hardware.

Work in order

Step-by-step fix

1. 1

   Disconnect motors, relays and external modules, leaving only USB power.

2. 2

   Use a known data-capable USB cable and a stable computer port.

3. 3

   Open the serial monitor at the baud rate shown by the project and capture the full reset reason.

4. 4

   Upload a minimal blink or serial sketch using the correct board and flash settings.

5. 5

   Reconnect peripherals one at a time while monitoring the supply voltage.

6. 6

   Move devices away from boot strapping pins and power high-current loads separately with a shared ground.

7. 7

   If flash errors continue, erase flash and upload a minimal verified project before restoring the application.

If the main path does not work

• Lower Wi-Fi transmit power only as a diagnostic if resets begin during radio activity.
• Use a powered USB hub or regulated bench supply to test for brownout.

How to reduce repeat failures

Budget current realistically, decouple the supply near the board and log reset reasons during development.

Common questions