The strobe code works very well but using only 8 LEDs for the strobe configured in a circle does not work well. All of the LED strobes I have made before were in a line because I used perfboard and they used 16 or more LEDs. Having 8 LEDs in a circle makes the strobe hard to see because of the noise which makes it look like it is random. You can still tune a guitar but it is takes a lot longer. This was never a problem before because when they are in a line the mass of on LEDs was very distinguishable. To make sure the code was good I had modified it a little to output the detected signal and hooked it up to an external strobe and it worked just as always. Using only 8 LEDs did not look nearly as good as 16 LEDs so I am going to change the strobe to 16 LEDs for the next iteration. Having 16 LEDs makes the signal very clear and very easy and quick to tune. Problem now is that I need an extra pin for the extra 8 LEDs. Looks like I will need to go to the 20 pin version of the SAM D11. That is probably the right thing to do because I am sharing two LED pins with the programmer right now. Not that it does not work but probably not supported by the manufacturer. So now I am on the straight and narrow. And so will the LEDs because I want the next iteration to be the one I send out for others to try out and so no untested configurations - as much as possible. I uploaded the test code to github.