Merge pull request #3193 from adafruit/bass_synth

adding bass synth code

Author: BlitzCityDIY

MIDI_Bass_Synth_Stomp_Box/code.py

@@ -0,0 +1,101 @@
+# SPDX-FileCopyrightText: 2026 Liz Clark for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+"""Bass Synth MIDI Stomp Box"""
+
+import board
+import busio
+import adafruit_midi
+import keypad
+from digitalio import DigitalInOut, Direction
+# pylint: disable=unused-import
+from adafruit_midi.control_change import ControlChange
+from adafruit_midi.pitch_bend import PitchBend
+from adafruit_midi.note_off import NoteOff
+from adafruit_midi.note_on import NoteOn
+from adafruit_midi.program_change import ProgramChange
+from adafruit_ticks import ticks_ms, ticks_add, ticks_diff
+
+# status LED
+led = DigitalInOut(board.GP18)
+led.direction = Direction.OUTPUT
+led.value = True
+
+# UART MIDI
+uart = busio.UART(board.GP0, board.GP1, baudrate=31250)
+#  midi channel setup
+midi_out_channel = 1
+#  midi setup - UART out on GP0
+midi = adafruit_midi.MIDI(
+    midi_out=uart,
+    out_channel=(midi_out_channel - 1),
+)
+
+# foot switches as keypad object
+KEY_PINS = (
+    board.GP2,
+    board.GP3,
+    board.GP4,
+    board.GP5,
+    board.GP6,
+    board.GP7,
+    board.GP8,
+    board.GP9,
+    board.GP10,
+    board.GP11,
+    board.GP12,
+    board.GP13,
+    board.GP14,
+    board.GP15,
+)
+notes = [48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59]
+keys = keypad.Keys(KEY_PINS, value_when_pressed=False)
+
+# variables & states
+MIN_NOTE = 24 # lowest starting octave
+MAX_NOTE = 84 # highest starting octave
+channel_num = midi.out_channel # track channel
+pressed_channel = False # did we try to change the MIDI channel
+blink_count = 0 # number of times the LED has blinked
+clock = ticks_ms() # time keeping
+blink_timer = 500 # blink interval (0.5 seconds)
+
+while True:
+    event = keys.events.get()
+    if event:
+        if event.pressed:
+            if event.key_number == 12:
+                # change MIDI channel
+                channel_num = (channel_num + 1) % 16
+                midi.out_channel = channel_num
+                print(channel_num + 1)
+                pressed_channel = True
+                led.value = False
+                blink_count = 0
+                clock = ticks_ms()
+            elif event.key_number == 13:
+                # checks if transposing the first note (C) by 1 octave would exceed the MAX_NOTE
+                # if it does, wraps the array down to start at MIN_NOTE
+                # otherwise, transposes all notes up by one octave
+                notes = [MIN_NOTE + (n - notes[0]) if notes[0] + 12 > MAX_NOTE
+                                                   else n + 12 for n in notes]
+            else:
+                # otherwise send noteOn message
+                midi.send(NoteOn(notes[event.key_number], 120))
+        if event.released:
+            if event.key_number < 12:
+                midi.send(NoteOff(notes[event.key_number], 120))
+    if pressed_channel:
+        # blink LED to show what MIDI channel we're on
+        if ticks_diff(ticks_ms(), clock) > blink_timer:
+            if not led.value:
+                led.value = True
+                blink_count += 1
+            else:
+                led.value = False
+            clock = ticks_add(clock, blink_timer)
+        # reset after blinking
+        if blink_count == (channel_num + 1):
+            pressed_channel = False
+            blink_count = 0
+            led.value = True