diff --git a/src/kaleidoscope/device/kbdfans/KBD4x.cpp b/src/kaleidoscope/device/kbdfans/KBD4x.cpp
index 963cbd67..8bc6c8d6 100644
--- a/src/kaleidoscope/device/kbdfans/KBD4x.cpp
+++ b/src/kaleidoscope/device/kbdfans/KBD4x.cpp
@@ -1,6 +1,6 @@
 /* -*- mode: c++ -*-
  * Kaleidoscope-Hardware-KBDFans-KBD4x -- KBD4x hardware support for Kaleidoscope
- * Copyright (C) 2019  Keyboard.io, Inc
+ * Copyright (C) 2019, 2020  Keyboard.io, Inc
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of version 3 of the GNU General Public License as
@@ -18,20 +18,55 @@
 #ifndef KALEIDOSCOPE_VIRTUAL_BUILD
 #ifdef ARDUINO_AVR_KBD4X
 
-#include "kaleidoscope/key_events.h"
-#include "kaleidoscope/driver/keyscanner/ATmega.h"
-#include "kaleidoscope/driver/keyscanner/Base_Impl.h"
 #include "kaleidoscope/Runtime.h"
+#include "kaleidoscope/driver/keyscanner/Base_Impl.h"
+
+
+// Here, we set up aliases to the device's KeyScanner and KeyScannerProps 
+// in the global namespace within the scope of this file. We'll use these
+// aliases to simplify some template initialization code below.
+using KeyScannerProps = typename kaleidoscope::device::kbdfans::KBD4xProps::KeyScannerProps;
+using KeyScanner = typename kaleidoscope::device::kbdfans::KBD4xProps::KeyScanner;
 
 namespace kaleidoscope {
 namespace device {
 namespace kbdfans {
 
-ATMEGA_KEYSCANNER_BOILERPLATE
+// `KeyScannerProps` here refers to the alias set up above. We do not need to
+// prefix the `matrix_rows` and `matrix_columns` names within the array
+// declaration, because those are resolved within the context of the class, so
+// the `matrix_rows` in `KeyScannerProps::matrix_row_pins[matrix_rows]` gets
+// resolved as `KeyScannerProps::matrix_rows`.
+const uint8_t KeyScannerProps::matrix_rows;
+const uint8_t KeyScannerProps::matrix_columns;
+constexpr uint8_t KeyScannerProps::matrix_row_pins[matrix_rows];
+constexpr uint8_t KeyScannerProps::matrix_col_pins[matrix_columns];
 
+// Resolving is a bit different in case of templates, however: the name of the
+// array is resolved within the scope of the namespace and the class, but the
+// array size is not - because it is a template. Therefore, we need a fully
+// qualified name there - or an alias in the global scope, which we set up just
+// above.
+template<> uint16_t KeyScanner::previousKeyState_[KeyScannerProps::matrix_rows] = {};
+template<> uint16_t KeyScanner::keyState_[KeyScannerProps::matrix_rows] = {};
+template<> uint16_t KeyScanner::masks_[KeyScannerProps::matrix_rows] = {};
+template<> uint8_t KeyScanner::debounce_matrix_[KeyScannerProps::matrix_rows][KeyScannerProps::matrix_columns] = {};
+
+// We set up the TIMER1 interrupt vector here. Due to dependency reasons, this
+// cannot be in a header-only driver, and must be placed here.
+//
+// Timer1 is responsible for setting a property on the KeyScanner, which will
+// tell it to do a scan. We use this to make sure that scans happen at roughly
+// the intervals we want. We do the scan outside of the interrupt scope for
+// practical reasons: guarding every codepath against interrupts that can be
+// reached from the scan is far too tedious, for very little gain.
+ISR(TIMER1_OVF_vect) {
+  Runtime.device().keyScanner().do_scan_ = true;
 }
-}
-}
+
+} // namespace kbdfans
+} // namespace device
+} // namespace kaleidoscope
 
 #endif
 #endif // ifndef KALEIDOSCOPE_VIRTUAL_BUILD
diff --git a/src/kaleidoscope/device/kbdfans/KBD4x.h b/src/kaleidoscope/device/kbdfans/KBD4x.h
index ba1da85f..5a58bc39 100644
--- a/src/kaleidoscope/device/kbdfans/KBD4x.h
+++ b/src/kaleidoscope/device/kbdfans/KBD4x.h
@@ -1,6 +1,6 @@
 /* -*- mode: c++ -*-
  * Kaleidoscope-Hardware-KBDFans-KBD4x -- KBD4x hardware support for Kaleidoscope
- * Copyright (C) 2019  Keyboard.io, Inc
+ * Copyright (C) 2019, 2020  Keyboard.io, Inc
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of version 3 of the GNU General Public License as
@@ -38,10 +38,13 @@ struct KBD4xProps : kaleidoscope::device::ATmega32U4KeyboardProps {
   };
   typedef kaleidoscope::driver::mcu::ATmega32U4<MCUProps> MCU;
   struct KeyScannerProps : public kaleidoscope::driver::keyscanner::ATmegaProps {
-    ATMEGA_KEYSCANNER_PROPS(
-      ROW_PIN_LIST({ PIN_D0, PIN_D1, PIN_D2, PIN_D3 }),
-      COL_PIN_LIST({ PIN_F0, PIN_F1, PIN_F4, PIN_F5, PIN_F6, PIN_F7, PIN_B3, PIN_B1, PIN_B0, PIN_D5, PIN_B7, PIN_C7 })
-    );
+    static constexpr uint8_t matrix_rows = 4;
+    static constexpr uint8_t matrix_columns = 12;
+    typedef MatrixAddr<matrix_rows, matrix_columns> KeyAddr;
+#ifndef KALEIDOSCOPE_VIRTUAL_BUILD
+    static constexpr uint8_t matrix_row_pins[matrix_rows] = {PIN_D0, PIN_D1, PIN_D2, PIN_D3};
+    static constexpr uint8_t matrix_col_pins[matrix_columns] = { PIN_F0, PIN_F1, PIN_F4, PIN_F5, PIN_F6, PIN_F7, PIN_B3, PIN_B1, PIN_B0, PIN_D5, PIN_B7, PIN_C7 };
+#endif // KALEIDOSCOPE_VIRTUAL_BUILD
   };
   typedef kaleidoscope::driver::keyscanner::ATmega<KeyScannerProps> KeyScanner;
   typedef kaleidoscope::driver::bootloader::avr::FLIP Bootloader;
@@ -49,9 +52,15 @@ struct KBD4xProps : kaleidoscope::device::ATmega32U4KeyboardProps {
 };
 
 #ifndef KALEIDOSCOPE_VIRTUAL_BUILD
-ATMEGA32U4_DEVICE(KBD4x);
+class KBD4x: public kaleidoscope::device::ATmega32U4Keyboard<KBD4xProps> {};
 #else // ifndef KALEIDOSCOPE_VIRTUAL_BUILD
+/* Device definition omitted for virtual device builds.
+ * We need to forward declare the device name, though, as there are
+ * some legacy extern references to boards whose definition
+ * depends on this.
+ */
 class KBD4x;
+
 #endif // ifndef KALEIDOSCOPE_VIRTUAL_BUILD
 
 #define PER_KEY_DATA(dflt,                                                       \