How to burn bootloader on the Nano-Every board?

1. Context

I'm cofounder of this new, free IDE for microcontrollers:

We're currently making lots of efforts to support Arduino boards and microcontrollers. The Arduino Nano-Every is next.

2. Goals

I bought a Nano-Every board from the Arduino shop. Uploading the firmware through the COM-port works just fine. However, I'd also like to burn the default bootloader to the microcontroller, such that we can add this functionality to Embeetle IDE.

As I understand, there are two MCUs on this board:

  • ATMega4809

  • SAMD11U

The ATMega4809 is clearly the central MCU where the sketch files end up. The SAMD11U seems to be an auxiliary MCU preconfigured as a USB-to-UART converter.

My main goal now, is to flash the default bootloader to the ATMega4809. If that works out well, I can try to flash the firmware of the SAMD11U (the same firmware it is preconfigured with), but that's just a bonus.

2.1 Flash bootloader ATMega4809

I can't see a connector for my Atmel-ICE or AVR ISP mkII, which I usually use to flash bootloaders. In comparison, the Arduino Uno and Leonardo have an ICSP connector at the bottom for that:

However, the Nano Every doesn't have such a connector. There is a 6-pin connector at the bottom (just copper dots, no pins), but that one seems to be connected to the SAMD11U MCU.

So here is my first question:

Question 1
Can I flash a bootloader to the ATMega4809 with my Atmel-ICE or AVR ISP mkII? If yes, how should I connect it?

When looking at the Arduino IDE, there seems to be an option to burn the ATMega4809 bootloader without an Atmel-ICE or AVR ISP mkII device:

You just have to select:
Programmer: "Onboard Atmel mEDBD (UNO WiFi Rev2)"
and then click Burn Bootloader.

At least, that's what this looks like to me. I'm not sure what this Programmer: "Onboard Atmel mEDBD (UNO WiFi Rev2)" actually represents. Is it the SAMD11U on the board? When I click Burn Bootloader, this is what I get:

avrdude -avrdude.conf

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean,
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "C:\Users\Gebruiker\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf"

         Using Port                    : usb
         Using Programmer              : xplainedmini_updi
avrdude: usbhid_open(): No device found
Error while burning bootloader.
avrdude: jtag3_open_common(): Did not find any device matching VID 0x03eb and PID list: 0x2145

avrdude done.  Thank you.

So here is my second question:

Question 2:
What is this option Programmer: "Onboard Atmel mEDBD (UNO WiFi Rev2)" in Arduino IDE? Why does the Burn Bootloader fail?


2.2 Flash firmwareSAMD11U

I didn't find a clear list-of-steps to achieve this: burning the default firmware to the SAMD11U chip on the Nano Every. I understand this is not needed for a Nano Every you buy from the Arduino Store, but I can imagine it is useful for people who design their own board.

Question 3:
How exactly do you burn the default firmware to the SAMD11U chip on the Nano Every board?

But this is just a nice-to-have question. Not my main goal for now.

It's connected to both. The pinout is shown on the "full pinout diagram" you can download from the "Documentation" tab of the Nano Every product page.


No. That's for the Microchip/Atmel mEDBG programmer, which is integrated onto the Arduino Uno WiFi Rev2 board. The Nano Every does not have an onboard mEDBG programmer.

Nano every doesn’t use a bootloader.
The samd11 actually contains chip-programming firmware.

Thank you @Juraj , @pert and @westfw for your help!

Flash firmware to ATMega4809

From your replies, I conclude that the ATMega4809 on the Nano-Every board has no bootloader. The SAMD11U acts as an on-board programmer device, to flash the firmware onto the ATMega4809.

In a way, this situation is comparable to the Nucleo boards from STMicroelectronics. They have an on-board STLink programmer/debugger device which flashes the firmware to the target STM32 processor.

With these Nucleo boards, you can break off the on-board STLink programmer, and flash the target STM32 chip with an external device - eg. a JLink, Blackmagic Probe, ...


Obviously, the Arduino Nano-Every wouldn't work anymore if you cut through it. But is there a way to flash firmware to the ATMega4809 with an external device (such as an AVR ISP mkII or Atmel-ICE)?

Flash firmware to SAMD11

To burn firmware into the SAMD11 chip, Juraj referred to this page:

There I read:

To reprogram the D11, simply power it while shorting SWDIO to GND pins. The board will appear as "MuxTo bootloader" and can be reprogammed using bossac or the IDE Upload button if you selected "Arduino MuxTO" target.

The page doesn't mention any external programmer device (such as an AVR ISP mkII or Atmel-ICE). So my conclusion is that the SAMD11 keeps its USB interface up and running while the SWDIO pin is grounded, using a bootloader to reflash its own firmware. Is that correct?

  1. see my first coment to a UPDI programmer and Per's link to pinout of the 6 dots
  2. the SAMD11 has a bootloader to replace the firmware.
    additional link to firmware update
    Serial interface locks up on Nano Every · Issue #51 · arduino/ArduinoCore-megaavr · GitHub