Flashing the Firmware

Use the MeshCore web flasher to load repeater firmware on one board and companion firmware on the other

This is the moment the two identical boards become two different things. Node 1 gets repeater firmware; node 2 gets companion firmware. Everything else in the course follows from this choice.

Before you start

• Fit the antennas to both boards (see the last lesson - this is not optional)
• Use Google Chrome or Microsoft Edge. The web flasher uses WebUSB, which Firefox and Safari do not support
• Have your USB-C data cable ready
• Label the boards. A strip of masking tape marked “REPEATER” and “CLIENT” will save you a lot of confusion in twenty minutes’ time

The firmware variants

At flasher.meshcore.io you will be offered several builds for the Heltec V3. The ones that matter to us:

Which companion build? Choose Companion (BLE) if you want to use your phone, which is what most people want. Choose Companion (USB Serial) if you plan to drive it from a laptop with the web client at app.meshcore.nz. You can always reflash later.

Flashing node 1 - the repeater

1. Fit the antenna, then plug the board into your computer with the USB-C data cable
2. Open flasher.meshcore.io in Chrome or Edge
3. Select your board: Heltec V3 (sometimes listed as Heltec WiFi LoRa 32 V3)
4. Select the firmware variant: Repeater
5. Select the region preset: EU/UK (Narrow) - more on this in the next lesson
6. Click Flash and pick your board’s serial port from the browser dialog. On Windows it appears as a COM port; on macOS it looks like /dev/cu.usbserial-xxxx or /dev/cu.SLAB_USBtoUART
7. Wait. The board reboots when it is done

If nothing appears in the port list, jump to the Common Issues at the bottom of this lesson.

Flashing node 2 - the client

Exactly the same process, with one change:

1. Unplug node 1, plug in node 2
2. Same board type: Heltec V3
3. Firmware variant: Companion (BLE)
4. Same region preset: EU/UK (Narrow) - both nodes must match
5. Flash

Did it work?

Look at the OLED screen.

• The repeater will show its name (something generic like MeshCore-a1b2 to begin with), plus uptime and packet counters
• The companion will show a Bluetooth pairing prompt or its node name, waiting for a phone to connect

If the screen is blank but the board is warm, the flash probably failed part way - just flash it again.

About the serial console

The flasher page has a built in console feature. This is how we will configure the repeater in lesson 7, so it is worth finding it now: flash the repeater, then look for the console or terminal option on the same page and connect to the board.

Type ver and press enter. If you get a firmware version back, you have a working console and the hard part is over.

There are two other ways to reach the same commands, and you may prefer them:

• config.meshcore.io - a friendlier web UI for repeater settings
• Any serial terminal at 115200 baud - screen, minicom, PuTTY, or the Arduino IDE serial monitor

Try it Yourself

1. Flash both boards, then swap the labels around and see if you can tell which is which from the OLED alone.
2. Connect the console to the repeater and run ver, board and stats-core. What is the board reporting for uptime?
3. Challenge: reflash node 2 as Companion (USB Serial), connect it to app.meshcore.nz, then put it back to BLE. Reflashing is cheap - get comfortable with it.

Common Issues

Problem: The browser shows no serial ports at all.

Solution: Try a different USB-C cable first, then a different USB port.

Why: Charge-only cables have no data lines. This is by far the most common cause.

Problem: “WebUSB is not supported” or the Flash button does nothing.

Solution: Use Chrome or Edge on a desktop.

Why: Firefox, Safari, and mobile browsers do not implement WebUSB.

Problem: The flash fails partway through or the board keeps rebooting.

Solution: Hold the BOOT button (marked PRG on some V3 boards) while plugging the USB cable in, then release it and flash again.

Why: This forces the ESP32-S3 into its bootloader instead of running whatever half-written firmware is on it.

Problem: I flashed the wrong variant.

Solution: Just flash it again with the right one.

Why: Nothing is permanent here. The only cost is a minute of your time.

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