ESP32-S3 / C3 — entering download mode:
- If your board has a RESET button (e.g. DevKitC, S3-Zero): hold BOOT, press and release RESET, then release BOOT.
- If your board has no RESET button (e.g. XIAO): hold BOOT, unplug USB, plug USB back in while still holding BOOT, then release.
The device will appear as a serial port. On Mac, if no port appears, ensure you are using a data cable (not a charge-only cable), and try a different USB port.