diff --git a/kmk/firmware.py b/kmk/firmware.py
index 389321d..363f46a 100644
--- a/kmk/firmware.py
+++ b/kmk/firmware.py
@@ -35,6 +35,9 @@ import kmk.internal_state  # isort:skip
 # Thanks for sticking around. Now let's do real work, starting below
 
 import gc
+import supervisor
+import board
+import busio
 
 from kmk.consts import LeaderMode, UnicodeModes
 from kmk.hid import USB_HID
@@ -59,6 +62,10 @@ class Firmware:
 
     hid_helper = USB_HID
 
+    split_type = None
+    split_offsets = ()
+    split_master_left = True
+
     def __init__(self):
         self._state = InternalState(self)
 
@@ -75,6 +82,54 @@ class Firmware:
             self._state.force_keycode_up(key)
             self._send_hid()
 
+    def _handle_update(self, update):
+        if self.split_type is not None and not self.split_master_left:
+            update[1] += self.split_offsets[update[1]]
+
+        if update is not None:
+            self._state.matrix_changed(
+                update[0],
+                update[1],
+                update[2],
+            )
+
+        if self._state.hid_pending:
+            self._send_hid()
+
+        for key in self._state.pending_keys:
+            self._send_key(key)
+            self._state.pending_key_handled()
+
+        if self._state.macro_pending:
+            for key in self._state.macro_pending(self):
+                self._send_key(key)
+
+            self._state.resolve_macro()
+
+        if self.debug_enabled:
+            print('New State: {}'.format(self._state._to_dict()))
+
+    def _send_to_master(self, update):
+        if self.split_type == "UART":
+            if self.uart is None:
+                self.uart = busio.UART(board.TX, board.RX, timeout=0)
+
+            # Update column with offset
+            if self.split_master_left:
+                update[1] += self.split_offsets[update[1]]
+
+            self.uart.write(update)
+
+    def _receive_from_slave(self):
+        if self.split_type == "UART":
+            if self.uart is None:
+                self.uart = busio.UART(board.TX, board.RX, timeout=0)
+
+            update = self.uart.read()
+            return update
+
+        return None
+
     def go(self):
         assert self.keymap, 'must define a keymap with at least one row'
         assert self.row_pins, 'no GPIO pins defined for matrix rows'
@@ -95,30 +150,18 @@ class Firmware:
             print("Firin' lazers. Keyboard is booted.")
 
         while True:
-            update = self.matrix.scan_for_changes()
-            if update is not None:
-                self._state.matrix_changed(
-                    update[0],
-                    update[1],
-                    update[2],
-                )
+            if self.split_type is not None:
+                update = self._receive_from_slave()
+                if update is not None:
+                    self._handle_update(update)
 
-                if self._state.hid_pending:
-                    self._send_hid()
+            for update in self.matrix.scan_for_changes():
+                # Abstract this later. Bluetooth will fail here
+                if supervisor.runtime.serial_connected:
+                    self._handle_update(update)
 
-                if self.debug_enabled:
-                    print('New State: {}'.format(self._state._to_dict()))
-
-            self._state.process_timeouts()
-
-            for key in self._state.pending_keys:
-                self._send_key(key)
-                self._state.pending_key_handled()
-
-            if self._state.macro_pending:
-                for key in self._state.macro_pending(self):
-                    self._send_key(key)
-
-                self._state.resolve_macro()
+                else:
+                    # This keyboard is a slave, and needs to send data to master
+                    self._send_to_master(update)
 
             gc.collect()
diff --git a/user_keymaps/kdb424/klanck.py b/user_keymaps/kdb424/klanck.py
index 8d3c9f4..fe593ab 100644
--- a/user_keymaps/kdb424/klanck.py
+++ b/user_keymaps/kdb424/klanck.py
@@ -16,9 +16,9 @@ keyboard.diode_orientation = DiodeOrientation.COLUMNS
 
 # ------------------User level config variables ---------------------------------------
 keyboard.unicode_mode = UnicodeModes.LINUX
-keyboard.tap_time = 900
+keyboard.tap_time = 350
 keyboard.leader_timeout = 2000
-keyboard.debug_enabled = True
+keyboard.debug_enabled = False
 
 emoticons = compile_unicode_string_sequences({
     # Emoticons, but fancier
diff --git a/user_keymaps/kdb424/levinson_m4.py b/user_keymaps/kdb424/levinson_m4.py
new file mode 100644
index 0000000..8d3c9f4
--- /dev/null
+++ b/user_keymaps/kdb424/levinson_m4.py
@@ -0,0 +1,90 @@
+from kmk.consts import DiodeOrientation, UnicodeModes
+from kmk.keycodes import KC
+from kmk.keycodes import generate_leader_dictionary_seq as glds
+from kmk.macros.simple import send_string
+from kmk.macros.unicode import compile_unicode_string_sequences
+from kmk.mcus.circuitpython_samd51 import Firmware
+from kmk.pins import Pin as P
+from kmk.types import AttrDict
+
+keyboard = Firmware()
+
+keyboard.col_pins = (P.A0, P.A1, P.A2, P.A3, P.A4, P.A5, P.SCK, P.MOSI, P.MISO, P.RX, P.TX, P.D4)
+keyboard.row_pins = (P.D10, P.D11, P.D12, P.D13)
+keyboard.diode_orientation = DiodeOrientation.COLUMNS
+
+
+# ------------------User level config variables ---------------------------------------
+keyboard.unicode_mode = UnicodeModes.LINUX
+keyboard.tap_time = 900
+keyboard.leader_timeout = 2000
+keyboard.debug_enabled = True
+
+emoticons = compile_unicode_string_sequences({
+    # Emoticons, but fancier
+    'ANGRY_TABLE_FLIP': r'(ノಠ痊ಠ)ノ彡┻━┻',
+    'CHEER': r'+｡:.ﾟヽ(´∀｡)ﾉﾟ.:｡+ﾟﾟ+｡:.ﾟヽ(*´∀)ﾉﾟ.:｡+ﾟ',
+    'TABLE_FLIP': r'(╯°□°）╯︵ ┻━┻',
+    'WAT': r'⊙.☉',
+    'FF': r'凸(ﾟДﾟ#)',
+    'F': r'（￣^￣）凸',
+    'MEH': r'╮(￣_￣)╭',
+    'YAY': r'o(^▽^)o',
+})
+
+# ---------------------- Leader Key Macros --------------------------------------------
+
+keyboard.leader_dictionary = {
+    glds('flip'): emoticons.ANGRY_TABLE_FLIP,
+    glds('cheer'): emoticons.CHEER,
+    glds('wat'): emoticons.WAT,
+    glds('ff'): emoticons.FF,
+    glds('f'): emoticons.F,
+    glds('meh'): emoticons.MEH,
+    glds('yay'): emoticons.YAY,
+}
+
+WPM = send_string("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Bibendum arcu vitae elementum curabitur vitae nunc sed. Facilisis sed odio morbi quis.")
+
+# ---------------------- Keymap ---------------------------------------------------------
+
+keyboard.keymap = [
+    [
+        # Default
+        [KC.GESC, KC.QUOTE, KC.COMMA, KC.DOT, KC.P, KC.Y, KC.F, KC.G, KC.C, KC.R, KC.L, KC.BKSP],
+        [KC.TAB, KC.A, KC.O, KC.E, KC.U, KC.I, KC.D, KC.H, KC.T, KC.N, KC.S, KC.ENT],
+        [KC.LSFT, KC.SCLN, KC.Q, KC.J, KC.K, KC.X, KC.B, KC.M, KC.W, KC.V, KC.Z, KC.SLSH],
+        [KC.LCTRL, KC.LGUI, KC.LALT, KC.LEAD, KC.MO(2), KC.LT(3, KC.SPC), KC.LT(3, KC.SPC), KC.MO(4), KC.LEFT, KC.DOWN, KC.UP, KC.RIGHT],
+    ],
+    [
+        # Gaming
+        [KC.TAB, KC.QUOT, KC.COMM, KC.DOT, KC.P, KC.Y, KC.F, KC.G, KC.C, KC.R, KC.L, KC.BKSP],
+        [KC.ESC, KC.A, KC.O, KC.E, KC.U, KC.I, KC.D, KC.H, KC.T, KC.N, KC.S, KC.ENT],
+        [KC.LSFT, KC.SCLN, KC.Q, KC.J, KC.K, KC.X, KC.B, KC.M, KC.W, KC.V, KC.Z, KC.SLSH],
+        [KC.LCTRL, KC.LGUI, KC.LALT, KC.F1, KC.F2, KC.SPC, KC.SPC, KC.MO(4), KC.LEFT, KC.DOWN, KC.UP, KC.RIGHT],
+    ],
+    [
+        # Raise1
+        [KC.TILD, KC.EXLM, KC.AT, KC.HASH, KC.DLR, KC.PERC, KC.CIRC, KC.AMPR, KC.ASTR, KC.LPRN, KC.RPRN, KC.DEL],
+        [KC.TRNS, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.LBRC, KC.RBRC, KC.BSLS],
+        [KC.TRNS, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.NO, KC.INS, KC.PGDN, KC.PGUP, KC.MINS],
+        [KC.RESET, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.NO, KC.NO, KC.EQL, KC.HOME, KC.VOLD, KC.VOLU, KC.END],
+    ],
+    [
+        # Raise2
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.N7, KC.N8, KC.N9, KC.BKSP],
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.N4, KC.N5, KC.N6, KC.NO],
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.N1, KC.N2, KC.N3, KC.NO],
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.N0, KC.N0, KC.PDOT, KC.ENT],
+    ],
+    [
+        # Raise3
+        [WPM, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.F10, KC.F11, KC.F12, KC.LSHIFT(KC.INS)],
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.F7, KC.F8, KC.F9, KC.NO],
+        [KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.F4, KC.F5, KC.F6, KC.NO],
+        [KC.DF(0), KC.DF(1), KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.F1, KC.F2, KC.F3, KC.NO],
+    ],
+]
+
+if __name__ == '__main__':
+    keyboard.go()