Logarithmic or linear selectable

code.py

@@ -2,8 +2,7 @@
 #
 # 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
 #
 # Upon run/power on, move expresson pedal from maximum to minimum to calibrate
@@ -21,6 +20,7 @@ import board
 import busio
 import analogio
 import digitalio
+import math
 import usb_midi
 import adafruit_midi
 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.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)
+# 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
 
-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
 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
+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
+usb_midi = adafruit_midi.MIDI(
+	midi_out=usb_midi.ports[1], out_channel=midi_channel - 1)
 
 # 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
+    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)
+    else:
+	    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
 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
-  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) / 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))
+        # 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))