diff --git a/src/kaleidoscope/MatrixAddr.h b/src/kaleidoscope/MatrixAddr.h
new file mode 100644
index 00000000..61aa9951
--- /dev/null
+++ b/src/kaleidoscope/MatrixAddr.h
@@ -0,0 +1,255 @@
+/* Kaleidoscope - Firmware for computer input devices
+ * Copyright (C) 2013-2019  Keyboard.io, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <limits.h>
+#include <stdint.h>
+
+namespace kaleidoscope {
+
+template<uint8_t rows__, uint8_t cols__>
+class MatrixAddr {
+ private:
+
+  uint8_t offset_;
+
+ public:
+
+  typedef MatrixAddr<rows__, cols__> ThisType;
+
+  static constexpr uint8_t rows = rows__;
+  static constexpr uint8_t cols = cols__;
+  static constexpr uint8_t upper_limit = rows__ * cols__;
+
+  static constexpr uint8_t invalid_state = 255;
+
+  static_assert(rows * cols < 255,
+                "The number of rows and columns provided to instanciate \n"
+                "MatrixAddr<rows, cols> exceeds the supported total number \n"
+                "of 255 keys");
+
+  constexpr MatrixAddr() : offset_(invalid_state) {}
+
+  constexpr MatrixAddr(uint8_t row, uint8_t col)
+    : offset_(row * cols + col) {}
+
+  constexpr MatrixAddr(uint8_t offset)
+    : offset_(offset) {}
+
+  // Rely on the default copy and move constructor.
+  //
+  // Note: If these were implemented naively as the commented versions below,
+  //       some versions of avr-gcc (e.g. 4.9.2 or 5.4 would generate
+  //       ridiculously bad assembler code for each copy construction,
+  //       that would bloat the default firmware by 1K of PROGMEM!
+  //
+  constexpr MatrixAddr(const ThisType &other) = default;
+  constexpr MatrixAddr(ThisType &&other) = default;
+  //constexpr MatrixAddr(const ThisType &other) : offset_(other.offset_) {}
+  //constexpr MatrixAddr(ThisType &&other) : offset_(other.offset_) {}
+
+  ThisType &operator=(const ThisType &) = default;
+  ThisType &operator=(ThisType &&) = default;
+
+  template<typename MatrixAddr__>
+  constexpr MatrixAddr(const MatrixAddr__ &other)
+    : MatrixAddr(other.row(), other.col()) {}
+
+  constexpr uint8_t row() const {
+    return offset_ / cols;
+  }
+  constexpr uint8_t col() const {
+    return offset_ % cols;
+  }
+
+  void setRow(uint8_t r) {
+    //assert(r < rows);
+    offset_ = this->col() + r * cols;
+  }
+  void setCol(uint8_t c) {
+    //assert(c < cols);
+    offset_ = this->row() * cols + c;
+  }
+
+  void shift(int8_t rows, int8_t cols) {
+    offset_ += rows * cols + cols;
+  }
+
+  void rowShift(int8_t rows) {
+    offset_ += rows * cols;
+  }
+
+  void colShift(int8_t cols) {
+    offset_ += cols;
+  }
+
+  constexpr ThisType shifted(int8_t row_offset, int8_t col_offset) const {
+    return ThisType(uint8_t(offset_ + row_offset * cols + col_offset));
+  }
+
+  constexpr ThisType rowShifted(int8_t row_offset) const {
+    return ThisType(uint8_t(offset_ + row_offset * cols));
+  }
+
+  constexpr ThisType colShifted(int8_t col_offset) const {
+    return ThisType(uint8_t(offset_ + col_offset));
+  }
+
+  constexpr uint8_t toInt() const {
+    return offset_;
+  }
+
+  constexpr bool isValid() const {
+    return offset_ < upper_limit;
+  }
+
+  ThisType operator++() {
+    ++offset_;
+    return *this;
+  }
+
+  ThisType operator++(int) { // postfix ++
+    ThisType copy(*this);
+    ++*this;         // call the prefix increment
+    return copy;
+  }
+
+  ThisType operator--() {
+    --offset_;
+    return *this;
+  }
+
+  ThisType operator--(int) { // postfix ++
+    ThisType copy(*this);
+    --*this;         // call the prefix increment
+    return copy;
+  }
+
+  template<typename MatrixAddr__>
+  ThisType &operator+(const MatrixAddr__ & other) {
+    *this = ThisType(this->row() + other.row(),
+                     this->col() + other.col());
+    return *this;
+  }
+
+  template<typename MatrixAddr__>
+  ThisType &operator-(const MatrixAddr__ & other) {
+    *this = ThisType(this->row() - other.row(),
+                     this->col() - other.col());
+    return *this;
+  }
+
+  template<typename MatrixAddr__>
+  ThisType &operator+=(const MatrixAddr__ & other) {
+    *this = *this + other;
+    return *this;
+  }
+
+  template<typename MatrixAddr__>
+  ThisType &operator-=(const MatrixAddr__ & other) {
+    *this = *this - other;
+    return *this;
+  }
+
+  bool operator==(const ThisType &other) const {
+    return offset_ == other.offset_;
+  }
+
+  bool operator!=(const ThisType &other) const {
+    return offset_ != other.offset_;
+  }
+
+  // Range is a helper class that is used in range based for loops
+  // over all possible KeyAddr values.
+  //
+  struct Range {
+    typedef ThisType Iterator;
+    static constexpr ThisType begin() {
+      return ThisType(uint8_t(0));
+    }
+    static constexpr ThisType end() {
+      return ThisType(ThisType::upper_limit);
+    }
+  };
+
+  // Use this method in range based for loops as e.g.
+  // for(auto key_addr: KeyAddr::all()) { ... }
+  //
+  static constexpr Range all() {
+    return Range{};
+  }
+
+  // This operator is needed to let MatrixAddr serve as Iterator type
+  // to iterate over a Range.
+  //
+  constexpr const ThisType &operator*() const {
+    return *this;
+  }
+};
+
+// Comparison operators only used for module testing. This is because they
+// cause ambiguous symbol lookup when used in the regular firmware.
+//
+// To use them also for the regular firmware they would need to be
+// disambiguated by moving them to the Kaleidoscope.h header and replacing
+// them with non-template versions that operate on the actual typedefed
+// KeyAddr and KeyAddr.
+
+#ifdef MATRIX_ADDR_TESTING
+
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator==(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  return (a1.row() == a2.row()) && (a1.col() == a2.col());
+}
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator!=(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  return !operator==(a1, a2);
+}
+
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator>(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  return (a1.row() > a2.row())
+         || ((a1.row() == a2.row()) && (a1.col() > a2.col()));
+}
+
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator<(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  // This could be optimized if necessary
+  return !operator>(a1, a2) && !operator==(a1, a2);
+}
+
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator>=(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  // This could be optimized if necessary
+  return operator>(a1, a2) || operator==(a1, a2);
+}
+
+template<typename MatrixAddr1__, typename MatrixAddr2__>
+bool operator<=(const MatrixAddr1__ & a1, const MatrixAddr2__ & a2) {
+  return !operator>(a1, a2);
+}
+
+#endif
+
+} // end namespace kaleidoscope
+
+// Row/col based access functions have been superseded by matrix address
+// base access.
+//
+#define _DEPRECATED_MESSAGE_ROW_COL_FUNC \
+   "Row/col based access functions have been deprecated. Please use " \
+   "the KeyAddr/KeyAddr based versions instead."