There are only few buttons on foot controllers and number of looper commands is much bigger. To deal with it multi tapping is used. If delay between taps is less than 0.5 seconds they belong to one series and produce MIDI note as explained below.
Assume button A sends note 60, velocity = 100. Multiple tapping will send one additional note 60 with changed velocity. Changed velocity = number of taps + 5 if the last tap had a long hold.
For this example:
Using multiple taps one button may send 6-7 different MIDI messages. Multiple taps use 0.5 seconds delay to decide if there will be next tap. Because of this it should not be used for time critical commands – start playing or recording. Use it for other commands like changing volume, scrolling song list, etc.
Midi input controller must send notes ON/OFF with velocity >10 because lower velocity values are used in multi tapping. All notes with velocity >10 are converted to velocity of 100 and this value is used in the menu configuration files.
Foot controller is coupled with three menu configuration files which translate MIDI notes and multiple taps into looper command, see [Menu configuration]
Notes are labelled: A, B, C, D, E, F and they correspond to integer values in keyboard_notes option in the [main.ini]
Velocity 100 is the standard velocity assigned to all original MIDI notes from controller. Velocity 1, 2, 3, ... 10 is velocity of counted note as explained above.
If foot controller sends control change (CC) messages from expression pedal the looper can convert them into notes. As example CC 12 will be converted to note 12 ON/OFF.
As an example in iRig Blue Board MIDI foot controller there are two expression pedal inputs. Plugging ON/OFF momentarily switches into these inputs will send CC messages converted into note messages.