The RC-5 asks a lot of one footswitch. Record, play, stop, double-tap, and hope you counted the taps right — all on a single pedal, in front of an audience. Adding an external footswitch takes the two commands you use most and gives them a pedal each. Here's how I wire an FS-6 to my RC-5, which two commands I map, and the one piece of BOSS's labelling that catches nearly everyone out.
Why a second footswitch is worth the trouble
The RC-5 is a compact single-track looper, and controlling every command from one switch can be genuinely difficult mid-performance. You click to record, click to play back, then double-tap to stop the track. The double-tap is where it goes wrong. A dedicated switch for stopping the loop removes that gesture entirely, and with it a good chunk of the margin for error in a live set. That's the whole argument: fewer ways to get it wrong when it counts.
Get a balanced TRS cable, not a guitar lead
This is the step people skip. You need a balanced TRS jack cable. A balanced TRS jack has two rings on the connector; a traditional guitar jack has only one. That difference matters because of how these footswitches work — pressing a switch sends a signal down the cable, and a dual footswitch like the FS-6 sends two different signals, one per switch. Two signals need two rings, one ring per footswitch, so the RC-5 can tell which switch you actually pressed. Use a standard guitar lead and the pedal simply won't receive both commands correctly.
Connect the FS-6 to the RC-5
Run the balanced TRS cable into the top connection on the RC-5, which is the STOP/MEMORY SHIFT jack. The other end goes into the A+B socket on the FS-6. That single cable carries both switches, which is exactly what you paid for with the extra ring.
Open the control menu
Head to Setup → Control. This is a system setting, so whatever you configure here is global across all of your memory banks — set it once and it behaves the same wherever you are on the pedal. Inside you'll find all of the pedal functions.
Leave the RC-5's own pedal function alone
The first setting is the pedal function for the RC-5's built-in footswitch. The default is Record Play Stop, and you can change it if you want to. I leave mine in the default state. The point of the exercise is to add switches, not to reshuffle the one you already know by feel.
Understand that Control Pedal 1 and 2 are inverted
Scroll to Control Pedal 1 and Control Pedal 2 — these are the two settings that refer to the FS-6's switches. Here's the part that isn't as transparent as you'd expect. You would fairly assume Control Pedal 1 is footswitch A and Control Pedal 2 is footswitch B. BOSS have inverted it. Control Pedal 1 is footswitch B, and Control Pedal 2 is footswitch A.
Tip: If you've mapped an external footswitch before and your commands ended up on the wrong pedal, this inversion is almost certainly why. Nothing is broken — the labels just don't mean what they look like they mean.
Set Control Pedal 1 to Track Clear
Control Pedal 1 is footswitch B, and I want that to be Track Clear — one press and the loop track on the RC-5 is gone, ready to start again on the same memory patch without breaking the performance. Go into the menu, click the memory/value knob encoder, and scroll through the available settings. There's a good variety in there — tap tempo, track reverse, and further down, track clear. Select it.
Set Control Pedal 2 to Track Play/Stop
Control Pedal 2 is footswitch A, and this is the one that kills the double-tap. Scrolling the same list you'll find Track Stop, but the better choice is Track Play/Stop — one switch that both starts and stops the loop. That's my pick, and it's the setting that does most of the work in this whole setup. You can exit the menu at this point; the remaining commands are for expression pedals and external MIDI foot remotes.
Test it before you trust it
With a loop already recorded, press footswitch A and the loop plays. Press it again and it stops — no double-tap. Then press footswitch B and the track clears. You'll see the confirmation on the display: the text turns blue where it was previously white, which tells you the loop is now blank and neutral. From there you can record a fresh loop, play it back, and clear it again. Run that cycle a few times at home so your feet know it before the room does.