cpx midi controller

Author: todbot

larger-tricks/cpx_midi_controller.py

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+# quick-n-dirty MIDI controller with Circuit Playground Express
+# 30 Apr 2024 - @todbot / Tod Kurt
+# Works on Circuit Playground Express in CircuitPython 9, 
+#  but will also work on also any board with touchio, like Trinket M0 or QTPy M0
+# Uses the minimal number of libraries to save RAM on the tiny M0 in the CPX
+#  (e.g. cannot load `adafruit_circuitpython`, `adafruit_midi`, and `adafruit_debouncer` on CPX)
+
+import board
+import touchio
+import usb_midi
+import neopixel
+
+# which MIDI notes to send
+midi_notenums = (40, 41, 42, 43)
+
+# which pins for each of the above notes
+touch_pins = (board.A1, board.A2, board.A3, board.A4)
+
+# which MIDI channel to transmit on
+midi_out_channel = 1
+
+# set up the status byte constants for sending MIDI later
+note_on_status = (0x90 | (midi_out_channel-1))
+note_off_status = (0x80 | (midi_out_channel-1))
+
+# get a MIDI out port
+midi_out = usb_midi.ports[1]
+# make ready the neopixels so we can blink when a pad is touched
+leds = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=0.1)
+
+# set up the touch pins
+touchins = []
+for i, pin in enumerate(touch_pins):
+    touchins.append( touchio.TouchIn(pin) )
+last_touch = [False] * len(touchins)
+
+print("Welcome! Touch a pad!")
+while True:
+    for i, touchin in enumerate(touchins):
+        touch = touchin.value          # get current touch value
+        if touch != last_touch[i]:     # was there a change in touch?
+            last_touch[i] = touch      # save for next time
+            notenum = midi_notenums[i] # get MIDI note for this pad
+            if touch                 : # pressed!
+                print("touch!", i)
+                midi_out.write(bytearray([note_on_status, notenum, 127]))
+                leds.fill(0x330044)
+            else:
+                print("release!",i)
+                midi_out.write(bytearray([note_off_status, notenum, 0]))
+                leds.fill(0)