CircuitPython, adafruit_midi rewrite. USB capable (#4)

code.py

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+################################################################################
+#
+# Pi-Pico-ExpressionPedal2Midi
+#
+# Connect an expression pedal to ADC0, a midi out socket/cable to UART1 if not
+# using USB midi. Midi messages are sent simultaneoulsy to UART1 and USB. 
+# Set desired midi channel, change control, and maximum and minimum values
+#
+# Upon run/power on, move expresson pedal from maximum to minimum to calibrate
+# your pedal. CC commands will immediately start sending once calibrated.
+#
+# Ashley Strahle
+# https://github.com/ashstrahle
+#
+################################################################################
+
+import sys
+import struct
+import time
+import board
+import busio
+import analogio
+import digitalio
+import usb_midi
+import adafruit_midi
+from adafruit_midi.timing_clock import TimingClock
+from adafruit_midi.note_on import NoteOn
+from adafruit_midi.note_off import NoteOff
+from adafruit_midi.pitch_bend import PitchBend
+from adafruit_midi.control_change import ControlChange
+
+# Midi settings
+midi_channel = 1 # Target midi channel to write to
+cc = 68 # Target Control Change number - this is for Behringer X32 Matrix 5
+cc_min = 20 # Minimum desired CC output
+cc_max = 97 # Maximum desired CC output (only want fader to go to unity gain - hence not 127)
+
+exp_pedal_calibration_percent = 80 # Required percentage of expression pedal movement for calibration 
+
+# Devices
+led = digitalio.DigitalInOut(board.LED)
+led.direction = digitalio.Direction.OUTPUT
+exp = analogio.AnalogIn(board.GP26) # Expression pedal device on pin 31
+uart = busio.UART(tx=board.GP4, rx=board.GP5, baudrate=31250, timeout=0.001) # UART Midi device on pin 6
+uart_midi = adafruit_midi.MIDI(midi_out=uart, out_channel=midi_channel - 1)
+usb_midi = adafruit_midi.MIDI(midi_out=usb_midi.ports[1], out_channel=midi_channel - 1)
+
+# Initialise variables
+# Set these to reverse thresholds to enable calibration
+exp_min = 65535 
+exp_max = 1
+
+exp_calibration_threshold = int(abs(exp_max - exp_min) * exp_pedal_calibration_percent / 100)
+cc_ratio = 1/(cc_max - cc_min) # Calculate number of possible CC values
+
+# This function translates the expression pedal value to the equivalent CC value
+def translate(exp_val):
+  ret = int((((exp_val - exp_min) * (cc_max - cc_min)) / (exp_max - exp_min)) + cc_min)
+  if ret > 0:
+    return ret
+  else:
+    return 0
+
+exp_previous = exp.value
+while True:
+  exp_current = exp.value
+
+  # Only process if the change ratio is greater than the possible number of CC values
+  if abs(exp_current - exp_previous) / exp_max > cc_ratio: 
+    if exp_current > exp_max:
+      exp_max = exp_current
+    elif exp_current < exp_min:
+      exp_min = exp_current
+    exp_previous = exp_current
+
+    # Only send midi when calibration threshold has been reached
+    if exp_max - exp_min > exp_calibration_threshold: 
+      led.value = True # Turn led on
+      cc_val = translate(exp_current)
+      uart_midi.send(ControlChange(cc, cc_val))
+      usb_midi.send(ControlChange(cc, cc_val))
+      led.value = False # Turn led off
+      print("Writing Midi Channel: {}, ControlChange: {}, Value {}. Exp Pedal: cur: {}, min: {}, max: {}".format(midi_channel, cc, cc_val, exp_current, exp_min, exp_max))