USB NKRO example for MacroPad

CircuitPython_MacroPad_NKRO/boot.py

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+import usb_hid
+
+BITMAP_KEYBOARD_DESCRIPTOR_REPORT_ID = 7
+REPORT_BYTES = 16
+bitmap_keyboard_descriptor = bytes((
+        0x05, 0x01,                     # Usage Page (Generic Desktop),
+        0x09, 0x06,                     # Usage (Keyboard),
+        0xA1, 0x01,                     # Collection (Application),
+        0x85, 0xFF,                     #   6,7 Report ID  [SET AT RUNTIME]
+        # bitmap of modifiers
+        0x75, 0x01,                     #   Report Size (1),
+        0x95, 0x08,                     #   Report Count (8),
+        0x05, 0x07,                     #   Usage Page (Key Codes),
+        0x19, 0xE0,                     #   Usage Minimum (224),
+        0x29, 0xE7,                     #   Usage Maximum (231),
+        0x15, 0x00,                     #   Logical Minimum (0),
+        0x25, 0x01,                     #   Logical Maximum (1),
+        0x81, 0x02,                     #   Input (Data, Variable, Absolute), ;Modifier byte
+        # LED output report
+        0x95, 0x05,                     #   Report Count (5),
+        0x75, 0x01,                     #   Report Size (1),
+        0x05, 0x08,                     #   Usage Page (LEDs),
+        0x19, 0x01,                     #   Usage Minimum (1),
+        0x29, 0x05,                     #   Usage Maximum (5),
+        0x91, 0x02,                     #   Output (Data, Variable, Absolute),
+        0x95, 0x01,                     #   Report Count (1),
+        0x75, 0x03,                     #   Report Size (3),
+        0x91, 0x03,                     #   Output (Constant),
+        # bitmap of keys
+        0x95, (REPORT_BYTES-1)*8,       #   Report Count (),
+        0x75, 0x01,                     #   Report Size (1),
+        0x15, 0x00,                     #   Logical Minimum (0),
+        0x25, 0x01,                     #   Logical Maximum(1),
+        0x05, 0x07,                     #   Usage Page (Key Codes),
+        0x19, 0x00,                     #   Usage Minimum (0),
+        0x29, (REPORT_BYTES-1)*8-1,     #   Usage Maximum (),
+        0x81, 0x02,                     #   Input (Data, Variable, Absolute),
+        0xc0                            # End Collection
+))
+
+bitmap_keyboard = usb_hid.Device(
+    report_descriptor = bitmap_keyboard_descriptor,
+    usage_page = 0x1,
+    usage = 0x6,
+    in_report_length = 16,
+    out_report_length = 1,
+    report_id_index = BITMAP_KEYBOARD_DESCRIPTOR_REPORT_ID,
+)
+
+print(bitmap_keyboard)
+devices = [
+    bitmap_keyboard,
+    usb_hid.Device.CONSUMER_CONTROL,
+    usb_hid.Device.MOUSE,
+]
+usb_hid.enable(devices)
+print("enabled HID with custom keyboard device") 

CircuitPython_MacroPad_NKRO/code.py

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+import keypad
+import board
+import usb_hid
+from adafruit_hid.keyboard import Keyboard, find_device
+from adafruit_hid.keycode import Keycode
+
+key_pins = (
+    board.KEY1,
+    board.KEY2,
+    board.KEY3,
+    board.KEY4,
+    board.KEY5,
+    board.KEY6,
+    board.KEY7,
+    board.KEY8,
+    board.KEY9,
+    board.KEY10,
+    board.KEY11,
+    board.KEY12,
+)
+
+keys = keypad.Keys(key_pins, value_when_pressed=False, pull=True)
+
+class BitmapKeyboard(Keyboard):
+    def __init__(self, devices):
+        device = find_device(devices, usage_page=0x1, usage=0x6)
+
+        try:
+            device.send_report(b'\0' * 16)
+        except ValueError:
+            print("found keyboard, but it did not accept a 16-byte report. check that boot.py is installed properly")
+
+        self._keyboard_device = device
+
+        # report[0] modifiers
+        # report[1:16] regular key presses bitmask
+        self.report = bytearray(16)
+
+        self.report_modifier = memoryview(self.report)[0:1]
+        self.report_bitmap = memoryview(self.report)[1:]
+
+    def _add_keycode_to_report(self, keycode):
+        modifier = Keycode.modifier_bit(keycode)
+        if modifier:
+            # Set bit for this modifier.
+            self.report_modifier[0] |= modifier
+        else:
+            self.report_bitmap[keycode >> 3] |= 1 << (keycode & 0x7)
+
+    def _remove_keycode_from_report(self, keycode):
+        modifier = Keycode.modifier_bit(keycode)
+        if modifier:
+            # Set bit for this modifier.
+            self.report_modifier[0] &= ~modifier
+        else:
+            self.report_bitmap[keycode >> 3] &= ~(1 << (keycode & 0x7))
+        
+    def release_all(self):
+        for i in range(len(self.report)):
+            self.report[i] = 0
+        self._keyboard_device.send_report(self.report)
+
+kbd = BitmapKeyboard(usb_hid.devices)
+
+keymap = [
+    Keycode.ONE, Keycode.TWO, Keycode.THREE,
+    Keycode.Q, Keycode.W, Keycode.E,
+    Keycode.A, Keycode.S, Keycode.D,
+    Keycode.Z, Keycode.X, Keycode.C]
+
+while True:
+    ev = keys.events.get()
+    if ev is not None:
+        key = keymap[ev.key_number]
+        if ev.pressed:
+            kbd.press(key)
+        else:
+            kbd.release(key)