ash/Pi-Pico-ExpressionPedal2Midi
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Ashley Strahle
2023-06-25 11:12:39 +10:00
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legacy/README.md
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# Legacy Notes
This is the original MicroPython version of Pi-PicoExpressionPedal2Midi, and only outputs to UART1 (no USB).
Kept here for reference.

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legacy/main.py
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################################################################################
#
# Pi-Pico-ExpressionPedal2Midi
#
# Connect an expression pedal to ADC0, and a midi out socket/cable to UART1.
# 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
from machine import ADC, Pin, UART
import ustruct
import time
# Constants
ControlChange = 0xb0
# 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
exp = machine.ADC(Pin(26)) # Expression pedal device on pin 31
uart = machine.UART(1, 31250) # UART Midi device on pin 6
led = machine.Pin(25, Pin.OUT) # Pico onboard led
# 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.read_u16()
while True:
exp_current = exp.read_u16()
# 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(1) # Turn led on
cc_val = translate(exp_current)
uart.write(ustruct.pack("bbb", ControlChange + midi_channel - 1, cc, cc_val))
led.value(0) # 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))