Public Access
74 lines
3.5 KiB
Markdown
74 lines
3.5 KiB
Markdown
 
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# Flashing the Nano over WiFi
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[← Back to the README](../README.md)
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The ESP32 can flash the Nano for you, so you don't need a USB cable at the display:
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```sh
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pio run -e nano_ota -t upload
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```
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What happens:
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1. The uploader ([tools/nano_net_upload.py](../tools/nano_net_upload.py)) connects to the
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ESP32 on TCP port **2323** and tells it the bootloader's baud rate.
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2. The ESP32 pauses the clock and switches the relay off for 1 second, then on again. If
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the reset wire is fitted, it also pulses the Nano's RESET pin. This restarts the Nano,
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and its bootloader starts.
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3. The ESP32 switches its link to the bootloader's baud rate and passes bytes between
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WiFi and the Nano.
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4. The uploader writes the new firmware and reads it back to verify it.
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5. When the uploader disconnects, the ESP32 switches the relay off. The clock powers the
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Nano on again with the new firmware and continues.
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The display goes dark for the duration of the upload, which takes a few seconds.
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**Requirements**
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- The reply wire must be connected: Nano D1 (TX) → voltage divider → ESP32 GPIO 16. The
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uploader needs the bootloader's answers.
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- The ESP32 must be running firmware with the flash bridge (this version or newer).
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## Bootloaders
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Flashing the Nano's firmware never changes its bootloader. Both common Nano bootloaders
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are supported:
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| Bootloader | Baud | Starts after a power cycle | Reset wire |
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|------------|------|----------------------------|------------|
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| Old bootloader (ATmegaBOOT), the one this Nano has now | 57600 | Yes | Not needed |
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| Optiboot ("new bootloader") | 115200 | No, only after a reset-pin reset | **Required** |
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By default (`--baud=auto` in `upload_flags`) the uploader tries 57600 first and then
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115200. Set `--baud=57600` or `--baud=115200` to skip the other attempt.
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If you ever replace the bootloader with Optiboot:
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- Fit the reset wire: ESP32 GPIO → 1 kΩ → base of an NPN transistor (e.g. 2N2222 or
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BC547). Connect the collector to Nano RESET and the emitter to GND. Set `NANO_RESET_PIN` in
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`src/esp32/config.h` to that GPIO, for example `4`. The transistor keeps the Nano's 5 V
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reset line away from the 3.3 V ESP32 pin.
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- For uploads over USB, change `board` in the `nano` environment to `nanoatmega328new`.
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**Settings**
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- ESP32 IP address: `upload_port` in the `nano_ota` environment in `platformio.ini`. You
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can add a port number: `10.1.1.198:2323`. For a one-time different address, use
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`pio run -e nano_ota -t upload --upload-port 10.1.1.50`.
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- Port, reset pin and timings: `NANO_FLASH_PORT`, `NANO_RESET_PIN`, `NANO_POWER_OFF_TIME`
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and `NANO_RESET_DELAY` in `src/esp32/config.h`.
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**If it fails**
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| Message | Cause |
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|---------|-------|
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| `can't connect to ...` | Wrong IP address, or the ESP32 is offline |
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| `the ESP32 flash bridge didn't accept the request` | The ESP32 runs older firmware without the flash bridge. Flash it first (`esp32` or `esp32_usb`). |
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| `no answer from the Nano bootloader` | Reply wire missing, or the Nano has Optiboot and the reset wire is missing |
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| `bad reply to command ...` / `verify failed` | Connection problem. Try again. A failed upload can leave the Nano without working firmware, but the bootloader itself is never overwritten, so flashing again (over WiFi or USB) always fixes it. |
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The ESP32 ends the session after 10 seconds without data, so the clock always resumes,
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even if the uploader is interrupted.
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> **Security:** anyone on your network can connect to port 2323 and flash the Nano, just
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> like the ESP32's own OTA has no password. Keep the display on a trusted network.
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