################################################################################
#
# 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))