OK, well if you don't get the pulsing LED after a double reset then this means the bootloader is missing or damaged on the MKR WiFi 1010. I'm going to provide you with two different set of instructions for how you can install the bootloader. The first is a little more complicated, but can be done with items you may already have on hand. The second requires a specialized piece of hardware that most Arduino users don't already have (but is a useful thing to aquire anyway!).
You'll need:
- An extra Arduino board that runs at 3.3 V.
- An SD slot. This could be built into your Arduino board (e.g., MKR Zero), a shield (e.g., MKR SD Proto Shield), or one of the common SD modules.
- An SD card that fits your SD slot.
- A way to connect the SD card to your computer.
- A way to make the connections to the SWD pins on your target Arduino board. For the Nano 33 IoT and the MKR boards other than MKR1000, I like to use a 0.1" pitch 2x3 POGO adapter. You could also solder wires to the test points if you prefer. On the MKR boards other than the MKR1000, the SWD header is on the bottom of the board and is the footprint for a 0.1" pitch 2x3 SMD header (e.g., https://www.digikey.com/short/z3dvdv).
It is possible to use an Arduino board that runs at 5 V as the programmer, but you'll need to use level shifting circuitry on the programming lines to avoid exposing the target board to 5 V logic levels, which would damage it.
Instructions:
Connect an SD card to your computer.
Open this link in your browser: ArduinoCore-samd/bootloaders at master · arduino/ArduinoCore-samd · GitHub
Click the folder that matches the name of your target board.
Click the file that ends in .bin.
Click the "Download" button.
Rename the downloaded file to fw.bin
Move fw.bin to the SD card.
Eject the SD card from your computer.
Plug the USB cable of the Arduino board you will be using as a programmer into your computer.
(In the Arduino IDE) Sketch > Include Library > Manage Libraries
Wait for the download to finish.
In the "Filter your search..." field, type "Adafruit DAP library".
Press "Enter".
Click on "Adafruit DAP library by Adafruit".
Click the "Install" button.
Wait for the installation to finish.
Click the "Close" button.
File > Examples > Adafruit DAP library > flash_from_SD
Change this line:
#define SD_CS 4
according to the Arduino pin connected to the SD CS pin. If your board has a built-in SD slot (e.g., MKR Zero), then you can change this line:
if (!SD.begin(SD_CS)) {
to:
if (!SD.begin()) {
Select the correct board from the Tools > Board menu.
Select the correct port from the Tools > Port menu.
Sketch > Upload
Wait for the upload to finish successfully.
Unplug the programmer Arduino board from your computer.
Plug the SD card into the SD slot connected to your Arduino board.
Connect the programmer Arduino board to the target Arduino board as follows:
| Programmer | | Target |
| - | - |
| ----------- | |------- |
| VCC | | +3V3 |
| ----------- | |------- |
| 10 | | SWDIO |
| ----------- | |------- |
| 9 | | SWCLK |
| ----------- | |------- |
| GND | | GND |
| ----------- | |------- |
| 11 | | RESETN |
| ----------- | |------- |
MKR board (except MKR 1000) SWD pads:
Plug the USB cable of the programmer Arduino board into your computer.
Tools > Serial Monitor. You should now see the target board detected, and the bootloader file flashed to it successfully.
Unplug the programmer Arduino board from your computer.
Disconnect the programmer Arduino board from the target Arduino board.
Note: if you have a CMSIS-DAP debugger, you can just do this instead:
- Connect the debugger to your Arduino board.
- (In the Arduino IDE) Tools > Programmer > Atmel EDBG
- Tools > Burn Bootloader
I use this little open source debugger.
