Understanding Boot Modes

Boot mode puts the ESP32‑S3 into a state where a host computer can upload firmware. The Nano ESP32 supports:

• Arduino UF2 bootloader: Double‑tap RESET. The board appears as a USB drive. Great for Arduino IDE and drag‑and‑drop updates.
• Espressif serial bootloader: Hold BOOT (GPIO0) then tap RESET. Used by esptool.py, Arduino CLI’s upload, PlatformIO, etc.

Methods to Enter Boot Mode

Method A — Arduino UF2 Bootloader (Double‑Tap RESET)

1. Connect the Nano ESP32 to your PC with a good USB‑C cable (data‑capable, not power‑only).
2. Double‑tap the RESET button quickly (two presses within ~0.5 seconds).
3. The board’s status LED will change pattern. Your computer should mount a new USB mass‑storage drive (name may include NANOESP32 or similar).
4. Upload via Arduino IDE or drag‑and‑drop a compatible UF2 file onto the drive.

Expected: A new drive appears; uploads succeed. If not, try another USB port/cable or Method B.

Method B — Espressif Serial Bootloader (Hold BOOT, Tap RESET)

1. Keep the board connected via USB.
2. Press and hold the BOOT button (this ties GPIO0 low).
3. While holding BOOT, press and release RESET.
4. Release BOOT after one second.
5. The chip is now in download (flash) mode. Start your upload (Arduino IDE/CLI, PlatformIO, or esptool.py).

Expected: The COM/tty port enumerates for flashing; the tool connects and uploads the firmware.

Method C — Automatic Boot Mode via IDE/CLI

Most tooling toggles boot mode automatically. Try:

arduino-cli board list
arduino-cli compile --fqbn arduino:esp32:nano_esp32 path/to/sketch
arduino-cli upload   --fqbn arduino:esp32:nano_esp32 -p  path/to/sketch

If auto‑reset fails, repeat the command immediately after performing Method B.

Troubleshooting

• No USB drive after double‑tap RESET: Use a different USB cable/port; try Method B; ensure board support is installed in Arduino IDE.
• Upload times out: Press BOOT + tap RESET (Method B) and retry the upload quickly.
• Wrong port: On Windows, check Device Manager; on macOS/Linux, check /dev/tty*. Replug the board to refresh ports.
• Power issues: Avoid long/poor cables and unpowered hubs; ensure stable 5V from USB.
• Driver conflicts: Close other serial monitors; only one program can hold the port at a time.

Quick Reference (Button Sequences)

• UF2 (Arduino): RESET double‑tap ⟶ mass‑storage drive appears.
• Serial (Espressif): Hold BOOT ⟶ tap RESET ⟶ release BOOT ⟶ flash via tool.

Example: esptool.py Manual Flash

Replace the port and binary paths as needed:

python -m esptool --chip esp32s3 -p COM7 -b 921600 \
  erase_flash

python -m esptool --chip esp32s3 -p COM7 -b 921600 \
  write_flash -z 0x0 firmware.bin

Enter serial bootloader first using Method B, then run the commands.