ash/Pi-Pico-ExpressionPedal2Midi
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Update to allow up to 3 expression pedals

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Ashley Strahle
2024-03-09 08:38:26 +10:00
parent e7193b6b4c
commit 6a0c72daf6
1 changed files with 45 additions and 47 deletions
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code.py
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@@ -1,8 +1,8 @@
################################################################################
#
# Pi-Pico-ExpressionPedal2Midi
# Pi-Pico-ExpressionPedal2Midi (Multiple Pedals)
#
# 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
#
# Upon run/power on, move expresson pedal from maximum to minimum to calibrate
@@ -30,69 +30,67 @@ from adafruit_midi.pitch_bend import PitchBend
from adafruit_midi.control_change import ControlChange
# Midi output settings
midi_channel = 1 # Target midi channel to write to
cc = 1 # Target Control Change number - Expression Pedal
cc_min = 0 # Minimum desired CC output - 0 - 127
cc_max = 127 # Maximum desired CC output - 0 - 127
midi_channel = 1 # Target midi channel
# 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
exp_pedal_calibration_percent = 80 # 0 - 100
# Define expression pedals
expression_pedals = [
# Set expression pedal midi control change number, and min/max values
{"pin": board.GP26, "cc": 1, cc_min: 0, cc_max: 127}, # Pedal 1. Pin 31
{"pin": board.GP27, "cc": 2, cc_min: 0, cc_max: 127}, # Pedal 2. Pin 32
{"pin": board.GP28, "cc": 3, cc_min: 0, cc_max: 127} # Peadl 3. Pin 34
]
# 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)
midi_out=usb_midi.ports[1], out_channel=midi_channel - 1)
# Initialize expression pedals
exp_values = [analogio.AnalogIn(pedal["pin"]) for pedal in expression_pedals]
exp_previous = [exp.value for exp in exp_values]
exp_min = [65535 for _ in expression_pedals]
exp_max = [1e-6 for _ in expression_pedals]
exp_calibration_threshold = [int(abs(exp_max[i] - exp_min[i]) * exp_pedal_calibration_percent / 100) for i in range(len(expression_pedals))]
# This function translates the expression pedal value to the equivalent CC value
def translate(exp_val):
def translate(exp_val, exp_min, exp_max, cc_min, cc_max):
if logarithmic:
scaled_val = math.log(exp_val, log_base) # Apply logarithmic scaling
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)
scaled_val = math.log(exp_val, log_base) # Apply logarithmic scaling
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:
return int((((exp_val - exp_min) * (cc_max - cc_min)) / (exp_max - exp_min)) + cc_min)
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
if exp_previous == 0:
exp_previous = offset
# main loop
# Main loop
while True:
exp_current = exp.value
if exp_current == 0:
exp_current = offset
for i, exp in enumerate(exp_values):
exp_current = exp.value
if exp_current == 0:
exp_current = 1e-6 # Small offset to avoid log(0) error
# 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 process if the change ratio is greater than the possible number of CC values
if abs(exp_current - exp_previous[i]) / exp_max[i] > 1/(cc_max[i] - cc_min[i]):
if exp_current > exp_max[i]:
exp_max[i] = exp_current
elif exp_current < exp_min[i]:
exp_min[i] = exp_current
exp_previous[i] = 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))
# Only send midi when calibration threshold has been reached
if exp_max[i] - exp_min[i] > exp_calibration_threshold[i]:
led.value = True # Turn led on
cc_val = translate(exp_current, exp_min[i], exp_max[i], cc_min[i], cc_max[i])
uart_midi.send(ControlChange(expression_pedals[i]["cc"], cc_val))
usb_midi.send(ControlChange(expression_pedals[i]["cc"], cc_val))
led.value = False # Turn led off
print("Pedal {}: Writing Midi Channel: {}, ControlChange: {}, Value {}. Exp Pedal: cur: {}, min: {}, max: {}".format(
i + 1, midi_channel, expression_pedals[i]["cc"], cc_val, exp_current, exp_min[i], exp_max[i]))