feat: add 'joystick2midi.py' example

Signed-off-by: Christopher Arndt <chris@chrisarndt.de>

Author: SpotlightKid

examples/joystick/joystick2midi.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python
+"""Convert joystick axis position into MIDI Control Change value in-/decrements."""
+
+import os
+import sys
+
+import pygame
+from rtmidi.midiutil import open_midioutput
+
+
+class Mapping:
+    def __init__(self, cc=7, ch=0, inc=1, minval=0, maxval=127):
+        self.cc = max(0, min(127, cc))
+        self.ch = max(0, min(15, ch))
+        self.minval = max(0, min(127, minval))
+        self.maxval = max(0, min(127, maxval))
+        self.inc = inc
+        self.value = 0.0
+        self.cc_value = -1
+
+    def update(self, value, threshold):
+        if abs(value) >= threshold:
+            self.value = max(self.minval, min(self.maxval, self.value + self.inc * value))
+
+            if int(self.value) != int(self.cc_value):
+                self.cc_value = self.value
+                return True
+
+
+# Configuration
+
+# How fast the joystick events are polled.
+UPDATES_PER_SECOND = 20
+# Axis absolute value must exceed this threshold before controler value changes
+THRESHOLD = 0.3
+# Which axis maps to which control change
+CONFIG = {
+    # Config for Axis 1
+    1: Mapping(cc=11, inc=-0.3),
+    # Config for Axis 0
+    0: Mapping(cc=12),
+    # etc...
+    4: Mapping(cc=15, inc=-0.3),
+    3: Mapping(cc=14),
+}
+
+# We need to init the pygame.display module to use the event queue
+os.environ["SDL_VIDEODRIVER"] = "dummy"
+pygame.display.init()
+clock = pygame.time.Clock()
+
+# Initialize the first joystick.
+pygame.joystick.init()
+
+if pygame.joystick.get_count():
+    joystick = pygame.joystick.Joystick(0)
+    joystick.init()
+else:
+    sys.exit("No joysticks found.")
+
+
+try:
+    midiout, name = open_midioutput(sys.argv[1] if len(sys.argv) > 1 else None)
+except (EOFError, KeyboardInterrupt):
+    sys.exit()
+else:
+    print("Opened MIDI output {}.".format(name))
+
+# Main Program Loop
+try:
+    # Loop until the user clicks the close button.
+    done = False
+    active = []
+
+    while not done:
+        # Possible joystick actions: JOYAXISMOTION, JOYBALLMOTION, JOYBUTTONDOWN,
+        # JOYBUTTONUP, JOYHATMOTION
+        for event in pygame.event.get(): # User did something.
+            if event.type == pygame.QUIT: # If user clicked close.
+                done = True # Flag that we are done so we exit this loop.
+            elif event.type == pygame.JOYBUTTONUP:
+                print("Joystick button {} released.".format(event.button))
+                if event.button == 2:  # 'X' button
+                    done = True
+                    print("Exit by button press.")
+            elif event.type == pygame.JOYAXISMOTION:
+                axis = event.axis
+                if axis in CONFIG:
+                    if abs(event.value) >= THRESHOLD:
+                        active.append(axis)
+                    elif axis in active:
+                        active.remove(axis)
+
+        # we're polling instead of using the event queue,
+        # so holding the joystick in one direction keeps updating the value
+        for axis in active:
+            mapping = CONFIG[axis]
+            value = joystick.get_axis(axis)
+
+            #print("Axis {} value: {:>6.3f}".format(axis, value))
+
+            if mapping.update(value, THRESHOLD):
+                msg = [0xB0 + mapping.ch, mapping.cc, int(mapping.value) & 0x7F]
+                print("SEND: {!r}".format(msg))
+                midiout.send_message(msg)
+
+
+        # Limit poll rate to UPDATES_PER_SECOND.
+        clock.tick(UPDATES_PER_SECOND)
+except KeyboardInterrupt:
+    print("\nInterrupted.")
+
+pygame.quit()