diff --git a/src/addr.h b/src/addr.h
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--- /dev/null
+++ b/src/addr.h
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+/* -*- mode: c++ -*-
+ * Kaleidoscope-Qukeys -- Assign two keycodes to a single key
+ * Copyright (C) 2017  Michael Richters
+ *
+ * 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, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 <Kaleidoscope.h>
+
+// Helper functions for converting between separate (row,col)
+// coordinates and a single-byte key number (addr). This works as long
+// as the keyboard has fewer than 256 keys.
+namespace kaleidoscope {
+  namespace addr {
+    inline uint8_t row(uint8_t key_addr) {
+      return (key_addr / COLS);
+    }
+    inline uint8_t col(uint8_t key_addr) {
+      return (key_addr % COLS);
+    }
+    inline uint8_t addr(uint8_t row, uint8_t col) {
+      return ((row * COLS) + col);
+    }
+  } // namespace addr {
+} // namespace kaleidoscope {