A three button switch is really just a two button switch with diodes in the wiring so that pressing the third switch simulates pressing both the other two at exactly the same time.
I seems to me you could use a three button switch if the firmware supported pressing both button together (the third button) so that it could be used for things like transitions rather than having to press and hold the main pedal.
Since the diodes can be in the switch, there would be no design changes needed to bb pedal itself.
Correct, another user is already doing this.
So is he/she doing something different with the third button or just triggering two things with a single button as though the user had pressed both at the same time. Or is there actually an option in the firmware for a āthirdā button that did not see?
Triggering both buttons
The Digitech Fs300 or Fs3x works with the BB
3rd button break/restart with the accent!
Yes, correct!
What would you like the third button to do?
Anything the other two could do. Itād just give you the ability to have three options for each situation (playing vs non playing) as opposed to two now.
Or how about pause but restart with a fill instead of the main part of the song.
You can already do that by tapping the footswitch button for a pause then, instead of tapping that footswitch button again, tapping the main pedal to restart with a fill.
Iām all for the idea of another button. Iād just like to know everything youād want to do with more buttons ā keep the ideas coming!
We know the time signature, so we know the length of the measuresā¦ What if we had a button that could help if you missed a cue. Press the button, and it repeats the last bar (or two) again? It could make the song more flexible live, even with preprogrammed songs.
the outro !
Tap Tempo 
āStartā song intro on press when main pedal is set to start on āreleaseā.
I have the Digitech FS 3X but donāt think it has any diodes and wonder what those diodes add ?
Yes it does. I opened mine up so you can seeā¦
Hereās a wiring diagram:
A TRS jack only has two circuits. One between tip and earth and one between ring and earth. You can āfakeā out a third switch on a two button switch (like the beatbuddy one) by simply pressing both switches at the same time. All the diodes and the third switch do is to let you do that with a single switch rather than having to get your foot over two switches. In addition, whatever is connected sees both lines being grounded at the same time. Pressing both switches on a two button switch (or the other two on a 3 button switch) can result in a slight delay between when the first switch grounds and when the second switch grounds.
You can handle that in software, no problem but using a single switch to ground both lines (via the diodes) means you need less of a delay if any, since you āknowā they are tied together and so both must be in effect, pressed at the same time.
Without the diodes in a three button switch, pressing ANY switch would result in whatever was connected ALWAYS seeing both lines earthed, making it in effect a one button switch!
Just got oneā¦about to plug it in and see what happens!
How were you able to set up the digitech?
Can the BB recognize the third button as it is, or will it need a firmware upgradeā¦? I tried my 3 button (diode equipped) footswitch and only 2 buttons seemed to workā¦
A third button option will give far more flexibilityā¦ Esp for people who mount BB on mic stands etcā¦
D
So far as I am aware, it would require a firmware upgrade to recognize the āthirdā button as as separate button. As it stands now I believe itās just the same as pressing BOTH buttons on the existing pedal at the same time so you get whatever effect or action is assigned to each individual button at the same time.