I was looking for a drum-machine, which I can interact with,
while playing an instrument like bass or guitar.
Nothing I found was really my thing, so I've mostly used what I
already had, together with an Arturia Beatstep 1
(hardware MIDI-sequencer). This isn't perfect, but near to what
I'm looking for.
The Beatstep is sending MIDI-notes to the RaspberryPi-samplerbox (https://www.samplerbox.org/),
which has a set of drum samples in my case.
The MIDI-Pedal is controlling the Beatstep via SysEx commands:
-PLAY and STOP should explain themselves
-TAP: Press two times for tap to tempo
-TMP+/-: Increase or decrease tempo by 10 BPM
-SEQ+/-: Jump the the next or previous pattern after current pattern
is finished
-An RGB-LED is pulsing to the beat (photo/video isn't recent.
Connected with three 500R-resitors on teensy-pins 23, 24 and 25).
Everything is powered by a 5V 1A PSU, connected via USB on the
Raspberry Pi.
And, because it's USB-MIDI: Don't forget to connect everything on
the software side via ALSA-MIDI (aconnect).