The bundled firmware (UF2) file is forked from Aboshi/SwitchME (https://github.com/Aboshi/SwitchME) with no modifications made.

I just wanted to document the fact that this works perfectly with the seeeduino xiao, as I couldn't find any reference to using the xiao as a Switch payload launcher.

The xiao needs to be powered externally while acting as a payload launcher, as the Switch does not provide power to the device itself.

I used a spare Arduino I had laying around to provide power to the xiao as it was the easiest way I could think to provide it 5v. It would be a much better idea to run this off of a battery.

Powering the xiao externally is very easy. Simply solder wires to the VIN and GND pads located underneath the xiao, on the edge furthest from the USB-C port, like so:

Then connect the wire attached to the VIN pad to a 5v power source. I chose to use the VCC port of a spare Arduino Pro Micro clone I had laying around. Also connect the wire attached to GND to something grounded, the GND pin of the Pro Micro, in this instance.

Installing the payload couldn't be easier, assuming you already have hekate set up on your Switch's SD card. Setting that up is outside the scope of this guide, but there are tons of tutorials online for getting hekate set up.

Simply download the hekate_ctcaer_5.5.3.UF2 file and drag it onto the "Arduino" drive that shows up when you plug in the xiao.

You should be ready to go, this is what my setup looked like when I had everything wired up:

And here's the money shot: