Implement basic HID keyboard support (send_string works great!)

kmk/micropython/pyb_hid.py

@@ -0,0 +1,122 @@
+import logging
+import string
+
+from pyb import USB_HID, delay
+
+from kmk.common.consts import Keycodes, char_lookup
+
+
+class HIDHelper:
+    '''
+    Wraps a HID reporting event. The structure of such events is (courtesy of
+    http://wiki.micropython.org/USB-HID-Keyboard-mode-example-a-password-dongle):
+
+    >Byte 0 is for a modifier key, or combination thereof. It is used as a
+    >bitmap, each bit mapped to a modifier:
+    >    bit 0: left control
+    >    bit 1: left shift
+    >    bit 2: left alt
+    >    bit 3: left GUI (Win/Apple/Meta key)
+    >    bit 4: right control
+    >    bit 5: right shift
+    >    bit 6: right alt
+    >    bit 7: right GUI
+    >
+    >    Examples: 0x02 for Shift, 0x05 for Control+Alt
+    >
+    >Byte 1 is "reserved" (unused, actually)
+    >Bytes 2-7 are for the actual key scancode(s) - up to 6 at a time ("chording").
+
+    Most methods here return `self` upon completion, allowing chaining:
+
+    ```python
+    myhid = HIDHelper()
+    myhid.send_string('testing').send_string(' ... and testing again')
+    ```
+    '''
+    def __init__(self, log_level=logging.NOTSET):
+        self.logger = logging.getLogger(__name__)
+        self.logger.setLevel(log_level)
+
+        self._hid = USB_HID()
+        self.clear_all()
+
+    def send(self):
+        self.logger.debug('Sending HID report: {}'.format(self._evt))
+        self._hid.send(self._evt)
+
+        return self
+
+    def send_string(self, message):
+        '''
+        Clears the HID report, and sends along a string of arbitrary length.
+        All keys will be released at the completion of the string. Modifiers
+        are not really supported here, though Shift will be pressed if
+        necessary to output the key.
+        '''
+
+        self.clear_all()
+        self.send()
+
+        for char in message:
+            kc = None
+            modifier = None
+
+            if char in char_lookup:
+                kc, modifier = char_lookup[char]
+            elif char in string.ascii_letters + string.digits:
+                kc = getattr(Keycodes.Common, 'KC_{}'.format(char.upper()))
+                modifier = Keycodes.Modifiers.KC_SHIFT if char.isupper() else None
+
+            if modifier:
+                self.enable_modifier(modifier)
+
+            self.add_key(kc)
+            self.send()
+
+            # Without this delay, events get clobbered and you'll likely end up with
+            # a string like `heloooooooooooooooo` rather than `hello`. This number
+            # may be able to be shrunken down. It may also make sense to use
+            # time.sleep_us or time.sleep_ms or time.sleep (platform dependent)
+            # on non-Pyboards.
+            delay(10)
+
+            # Release all keys or we'll forever hold whatever the last keypress was
+            self.clear_all()
+            self.send()
+
+        return self
+
+    def clear_all(self):
+        self._evt = bytearray(8)
+        return self
+
+    def clear_non_modifiers(self):
+        for pos in range(2, 8):
+            self._evt[pos] = 0x00
+
+        return self
+
+    def enable_modifier(self, modifier):
+        if Keycodes.Modifiers.contains(modifier):
+            self._evt[0] |= modifier
+            return self
+
+        raise ValueError('Attempted to use non-modifier as a modifier')
+
+    def add_key(self, key):
+        if key and Keycodes.contains(key):
+            # Try to find the first empty slot in the key report, and fill it
+            placed = False
+            for pos in range(2, 8):
+                if self._evt[pos] == 0x00:
+                    self._evt[pos] = key
+                    placed = True
+                    break
+
+            if not placed:
+                raise ValueError('Out of space in HID report, could not add key')
+
+            return self
+
+        raise ValueError('Invalid keycode?')