ash/Pi-Pico-ExpressionPedal2Midi
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Logarithmic or linear selectable

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Ashley Strahle
2023-06-25 11:04:35 +10:00
parent 594c6f6819
commit bac62aaa6f
1 changed files with 54 additions and 40 deletions
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code.py
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@@ -2,8 +2,7 @@
# #
# Pi-Pico-ExpressionPedal2Midi # 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.
# using USB midi. Midi messages are sent simultaneoulsy to UART1 and USB.
# Set desired midi channel, change control, and maximum and minimum values # Set desired midi channel, change control, and maximum and minimum values
# #
# Upon run/power on, move expresson pedal from maximum to minimum to calibrate # Upon run/power on, move expresson pedal from maximum to minimum to calibrate
@@ -21,6 +20,7 @@ import board
import busio import busio
import analogio import analogio
import digitalio import digitalio
import math
import usb_midi import usb_midi
import adafruit_midi import adafruit_midi
from adafruit_midi.timing_clock import TimingClock from adafruit_midi.timing_clock import TimingClock
@@ -29,55 +29,69 @@ from adafruit_midi.note_off import NoteOff
from adafruit_midi.pitch_bend import PitchBend from adafruit_midi.pitch_bend import PitchBend
from adafruit_midi.control_change import ControlChange from adafruit_midi.control_change import ControlChange
# Midi settings # Midi output settings
midi_channel = 1 # Target midi channel to write to midi_channel = 1 # Target midi channel to write to
cc = 68 # Target Control Change number - this is for Behringer X32 Matrix 5 cc = 1 # Target Control Change number - Expression Pedal
cc_min = 20 # Minimum desired CC output cc_min = 0 # Minimum desired CC output - 0 - 127
cc_max = 97 # Maximum desired CC output (only want fader to go to unity gain - hence not 127) cc_max = 127 # Maximum desired CC output - 0 - 127
exp_pedal_calibration_percent = 80 # Required percentage of expression pedal movement for calibration # Expression pedal settings
logarithmic = True # Expression pedal logarithmic or linear. Set to False for linear
log_base = 100 # This value changes the feel of the log curve
# Required percentage of expression pedal movement for calibration
exp_pedal_calibration_percent = 80 # 0 - 100
# Devices # Devices
led = digitalio.DigitalInOut(board.LED) led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT led.direction = digitalio.Direction.OUTPUT
exp = analogio.AnalogIn(board.GP26) # Expression pedal device on pin 31 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 = 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) 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) 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 # This function translates the expression pedal value to the equivalent CC value
def translate(exp_val): def translate(exp_val):
ret = int((((exp_val - exp_min) * (cc_max - cc_min)) / (exp_max - exp_min)) + cc_min) if logarithmic:
if ret > 0: scaled_val = math.log(exp_val, log_base) # Apply logarithmic scaling
return ret return int((((scaled_val - math.log(exp_min, log_base)) * (cc_max - cc_min)) / (math.log(exp_max, log_base) - math.log(exp_min, log_base))) + cc_min)
else: else:
return 0 return int((((exp_val - exp_min) * (cc_max - cc_min)) / (exp_max - exp_min)) + cc_min)
# Initialise variables
offset = 1e-6 # Small offset to avoid log(0) error
# Set these to reverse thresholds to enable calibration
exp_min = 65535
exp_max = offset
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
exp_previous = exp.value exp_previous = exp.value
if exp_previous == 0:
exp_previous = offset
# main loop
while True: while True:
exp_current = exp.value exp_current = exp.value
if exp_current == 0:
exp_current = offset
# Only process if the change ratio is greater than the possible number of CC values # 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 abs(exp_current - exp_previous) / exp_max > cc_ratio:
if exp_current > exp_max: if exp_current > exp_max:
exp_max = exp_current exp_max = exp_current
elif exp_current < exp_min: elif exp_current < exp_min:
exp_min = exp_current exp_min = exp_current
exp_previous = exp_current exp_previous = exp_current
# Only send midi when calibration threshold has been reached # Only send midi when calibration threshold has been reached
if exp_max - exp_min > exp_calibration_threshold: if exp_max - exp_min > exp_calibration_threshold:
led.value = True # Turn led on led.value = True # Turn led on
cc_val = translate(exp_current) cc_val = translate(exp_current)
uart_midi.send(ControlChange(cc, cc_val)) uart_midi.send(ControlChange(cc, cc_val))
usb_midi.send(ControlChange(cc, cc_val)) usb_midi.send(ControlChange(cc, cc_val))
led.value = False # Turn led off 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)) print("Writing Midi Channel: {}, ControlChange: {}, Value {}. Exp Pedal: cur: {}, min: {}, max: {}".format(
midi_channel, cc, cc_val, exp_current, exp_min, exp_max))