# Flashing the Firmware

## USB Serial Flashing

### Prerequisites

- USB cable connected to Heltec board
- User in `uucp` or `dialout` group (for `/dev/ttyUSB*` access)

### Flash Command

```bash
# Build and flash
pio run -t upload

# Flash to specific port
pio run -t upload --upload-port /dev/ttyUSB0
```

### Using the Stable Device Path

USB device numbers can change. Use the stable path instead:

```bash
pio run -t upload --upload-port /dev/serial/by-id/usb-Silicon_Labs_CP2102_USB_to_UART_Bridge_Controller_0001-if00-port0
```

### Boot Mode Issues

If flashing fails, manually enter bootloader mode:

1. Hold **BOOT** button
2. Press **RST** button
3. Release **BOOT** button
4. Run `pio run -t upload`

---

## OTA Updates

Over-The-Air updates let you flash wirelessly after initial USB flash.

### Step 1: Enter OTA Mode

Connect to serial console:
```bash
screen /dev/ttyUSB0 115200
```

Type:
```
start ota
```

Response:
```
Started: http://192.168.4.1/update
```

### Step 2: Connect to WiFi

The repeater creates an open access point:

- **SSID:** `MeshCore-OTA`
- **Password:** (none)

Connect your computer/phone to this network.

### Step 3: Upload Firmware

1. Open browser to `http://192.168.4.1/update`
2. Click "Choose File"
3. Select `.pio/build/heltec_v3_repeater/firmware.bin`
4. Click "Update"
5. Wait for upload and reboot (~30 seconds)

### OTA Endpoints

| URL | Purpose |
|-----|---------|
| `http://192.168.4.1/` | Device info page |
| `http://192.168.4.1/update` | ElegantOTA firmware upload |
| `http://192.168.4.1/log` | View packet log (if enabled) |

### Exiting OTA Mode

OTA mode stays active until reboot. To exit without updating:

- Press the **RST** button, or
- Power cycle the device

---

## Verifying the Flash

After flashing, connect to serial:

```bash
screen /dev/ttyUSB0 115200
```

Press **RST** to see boot messages:

```
Repeater ID: AABBCCDD...
```

Type `ver` to check firmware version:
```
ver
  -> MeshCore v1.10.0 (Jan 25 2025)
```

---

## Exit Screen

To exit the `screen` session:

- `Ctrl+a` then `k` then `y` (kill session)
- Or `Ctrl+a` then `d` (detach, keeps session running)