Squirt_5432:
I just tried double-pressing the reset button a few times at various speeds and still seeing no lights at all.
OK, if you're not getting a pulsing "L" LED after the double reset then it means the sketch overwrote your bootloader. So the fix is to replace the bootloader.
You'll need:
ARM CMSIS-DAP compatible programmer/debugger
Here's a reasonably priced one that's all open source: https://www.tindie.com/products/ataradov/cmsis-dap-compliant-swd-debugger.
But you're welcome to use whatever CMSIS-DAP programmer you prefer, that's just the one I happen to own.
In addition to allowing you to recover bricked boards, this programmer can be used for ICE debugging. I've used it with the Arduino SAMD boards and the Arduino Pro IDE and it works great.
There is a cool library that allows you to turn a spare Arduino board into a DAP programmer, but I haven't figured out whether it's possible to use it with the Nano 33 BLE.
Breakout board to allow you to easily make the connections between the debugger's 0.05" pitch connector and the Nano 33 BLE
Some way to make the connections to the SWD test pads on the Nano 33 BLE
Here's a handy pogo adapter: SparkFun ISP Pogo Adapter - KIT-11591 - SparkFun Electronics
(Also good for programming AVR boards via the ICSP footprint when you haven't added a header.)
Even with this adapter, it's a bit challenging to get the pogo pins aligned with the small test pads on the Nano 33 BLE, but if you keep at it you'll get it eventually.
Better would be to have a jig like this, but if you're not going to be doing this regularly then that's probably overkill.
Some people have managed to use a regular 0.1" pitch 2x3 male header pressed down on the test pads to make the connections. I think that would be a bit more challenging, but it's cheap enough and something you might already have on hand.
You also have the option of just soldering wires to the test pads on the Nano 33 BLE.
Process:
Start the Arduino IDE.
Tools > Board > Arduino Nano 33 BLE
Tools > Programmer > ARM CMSIS-DAP Compatible
Make the connections between the debugger/programmer and the Nano 33 BLE:
| Programmer | | Target |
| - | - |
| ----------- | |------- |
| VCC | | +3V3 |
| ----------- | |------- |
| SWDIO | | SWDIO |
| ----------- | |------- |
| SWCLK | | SWCLK |
| ----------- | |------- |
| GND | | GND |
| ----------- | |------- |
| RESET | | RESETN |
| ----------- | |------- |
Here's the pinout of the test pads on the Nano 33 BLE:
Connect the USB cable of the programmer to your computer.
Power the Nano 33 BLE (you can do this via the USB connector on the board). The debugger doesn't power the board.
Tools > Burn Bootloader