145 lines
4.5 KiB
Python
145 lines
4.5 KiB
Python
# SPDX-FileCopyrightText: 2023 John Park for Adafruit Industries
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# SPDX-License-Identifier: MIT
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# Grand Central MIDI Knobs
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# for USB MIDI and optional UART MIDI
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# Reads analog inputs, sends out MIDI CC values
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# with Kattni Rembor and Jan Goolsbey for range and hysteresis code
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import time
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import board
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import busio
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from simpleio import map_range
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from analogio import AnalogIn
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from digitalio import DigitalInOut, Direction
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import usb_midi
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import adafruit_midi # MIDI protocol encoder/decoder library
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from adafruit_midi.control_change import ControlChange
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# pick your USB MIDI out channel here, 1-16
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MIDI_USB_channel = 1
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# pick your classic MIDI channel for sending over UART serial TX/RX
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CLASSIC_MIDI_channel = 2
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midi_usb = adafruit_midi.MIDI(
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midi_out=usb_midi.ports[1], out_channel=MIDI_USB_channel - 1
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)
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# use DIN-5 or TRS MIDI jack on TX/RX for classic MIDI
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midi_uart = busio.UART(board.TX, board.RX, baudrate=31250, timeout=0.001) # initialize UART
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classic_midi = adafruit_midi.MIDI(
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midi_out=midi_uart, midi_in=midi_uart, out_channel=CLASSIC_MIDI_channel - 1, debug=False
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)
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led = DigitalInOut(board.D13) # activity indicator
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led.direction = Direction.OUTPUT
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knob_count = 16 # Set the total number of potentiometers used
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# Create the input objects list for potentiometers
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knob = []
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for k in range(knob_count):
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knobs = AnalogIn(
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getattr(board, "A{}".format(k))
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) # get pin # attribute, use string formatting
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knob.append(knobs)
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# assignment of knobs to cc numbers
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cc_number = [
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1, # knob 1, mod wheel
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2, # knob 2, breath control
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7, # knob 3, volume
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10, # knob 4 pan
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11, # knob 5, expression
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53, # knob 6
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54, # knob 7
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73, # knob 8
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74, # knob 9, Filter frequency cutoff
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71, # knob 10, Filter resonance
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58, # knob 11
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59, # knob 12
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60, # knob 13
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61, # knob 14
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62, # knob 15
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63, # knob 16
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]
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# CC range list defines the characteristics of the potentiometers
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# This list contains the input object, minimum value, and maximum value for each knob.
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# example ranges:
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# 0 min, 127 max: full range control voltage
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# 36 (C2) min, 84 (B5) max: 49-note keyboard
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# 21 (A0) min, 108 (C8) max: 88-note grand piano
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cc_range = [
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(0, 127), # knob 0: C2 to B5: 49-note keyboard
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(0, 127), # knob 1
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(0, 127), # knob 2
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(0, 127), # knob 3
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(0, 127), # knob 4
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(0, 127), # knob 5
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(0, 127), # knob 6
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(0, 127), # knob 7
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(0, 127), # knob 8
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(0, 127), # knob 9
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(0, 127), # knob 10
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(0, 127), # knob 11
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(0, 127), # knob 12
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(0, 127), # knob 13
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(0, 127), # knob 14
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(0, 127), # knob 15
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]
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print("---Grand Central MIDI Knobs---")
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print(" USB MIDI channel: {}".format(MIDI_USB_channel))
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print(" TRS MIDI channel: {}".format(CLASSIC_MIDI_channel))
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# Initialize cc_value list with current value and offset placeholders
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cc_value = []
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for _ in range(knob_count):
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cc_value.append((0, 0))
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last_cc_value = []
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for _ in range(knob_count):
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last_cc_value.append((0, 0))
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# range_index converts an analog value (ctl) to an indexed integer
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# Input is masked to 8 bits to reduce noise then a scaled hysteresis offset
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# is applied. The helper returns new index value (idx) and input
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# hysteresis offset (offset) based on the number of control slices (ctrl_max).
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def range_index(ctl, ctrl_max, old_idx, offset):
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if (ctl + offset > 65535) or (ctl + offset < 0):
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offset = 0
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idx = int(map_range((ctl + offset) & 0xFF00, 1200, 65500, 0, ctrl_max))
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if idx != old_idx: # if index changed, adjust hysteresis offset
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# offset is 25% of the control slice (65536/ctrl_max)
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offset = int(
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0.25 * sign(idx - old_idx) * (65535 / ctrl_max)
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) # edit 0.25 to adjust slices
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return idx, offset
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def sign(x): # determine the sign of x
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if x >= 0:
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return 1
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else:
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return -1
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while True:
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# read all the knob values
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for i in range(knob_count):
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cc_value[i] = range_index(
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knob[i].value,
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(cc_range[i][1] - cc_range[i][0] + 1),
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cc_value[i][0],
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cc_value[i][1],
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)
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if cc_value[i] != last_cc_value[i]: # only send if it changed
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# Form a MIDI CC message and send it:
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midi_usb.send(ControlChange(cc_number[i], cc_value[i][0] + cc_range[i][0]))
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classic_midi.send(
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ControlChange(cc_number[i], cc_value[i][0] + cc_range[i][0])
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)
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last_cc_value[i] = cc_value[i]
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led.value = True
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time.sleep(0.01)
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led.value = False
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