diff --git a/src/kaleidoscope/hardware/ErgoDox.h b/src/kaleidoscope/hardware/ErgoDox.h
index fbf63d80..afd90c59 100644
--- a/src/kaleidoscope/hardware/ErgoDox.h
+++ b/src/kaleidoscope/hardware/ErgoDox.h
@@ -161,4 +161,106 @@ class ErgoDox {
 }
 }
 
+/* To be used by the hardware implementations, `keyIndex` tells us the index of
+ * a key, from which we can figure out the row and column as needed. The index
+ * starts at one, so that plugins that work with a list of key indexes can use
+ * zero as a sentinel. This is important, because when we initialize arrays with
+ * fewer elements than the declared array size, the remaining elements will be
+ * zero. We can use this to avoid having to explicitly add a sentinel in
+ * user-facing code.
+ */
+constexpr byte keyIndex(byte row, byte col) {
+  return row * COLS + col + 1;
+}
+
+constexpr byte R0C0  = keyIndex(0, 0);
+constexpr byte R0C1  = keyIndex(0, 1);
+constexpr byte R0C2  = keyIndex(0, 2);
+constexpr byte R0C3  = keyIndex(0, 3);
+constexpr byte R0C4  = keyIndex(0, 4);
+constexpr byte R0C5  = keyIndex(0, 5);
+constexpr byte R0C6  = keyIndex(0, 6);
+constexpr byte R0C7  = keyIndex(0, 7);
+constexpr byte R0C8  = keyIndex(0, 8);
+constexpr byte R0C9  = keyIndex(0, 9);
+constexpr byte R0C10 = keyIndex(0, 10);
+constexpr byte R0C11 = keyIndex(0, 11);
+constexpr byte R0C12 = keyIndex(0, 12);
+constexpr byte R0C13 = keyIndex(0, 13);
+
+constexpr byte R1C0  = keyIndex(1, 0);
+constexpr byte R1C1  = keyIndex(1, 1);
+constexpr byte R1C2  = keyIndex(1, 2);
+constexpr byte R1C3  = keyIndex(1, 3);
+constexpr byte R1C4  = keyIndex(1, 4);
+constexpr byte R1C5  = keyIndex(1, 5);
+constexpr byte R1C6  = keyIndex(1, 6);
+constexpr byte R1C7  = keyIndex(1, 7);
+constexpr byte R1C8  = keyIndex(1, 8);
+constexpr byte R1C9  = keyIndex(1, 9);
+constexpr byte R1C10 = keyIndex(1, 10);
+constexpr byte R1C11 = keyIndex(1, 11);
+constexpr byte R1C12 = keyIndex(1, 12);
+constexpr byte R1C13 = keyIndex(1, 13);
+
+constexpr byte R2C0  = keyIndex(2, 0);
+constexpr byte R2C1  = keyIndex(2, 1);
+constexpr byte R2C2  = keyIndex(2, 2);
+constexpr byte R2C3  = keyIndex(2, 3);
+constexpr byte R2C4  = keyIndex(2, 4);
+constexpr byte R2C5  = keyIndex(2, 5);
+constexpr byte R2C6  = keyIndex(2, 6);
+constexpr byte R2C7  = keyIndex(2, 7);
+constexpr byte R2C8  = keyIndex(2, 8);
+constexpr byte R2C9  = keyIndex(2, 9);
+constexpr byte R2C10 = keyIndex(2, 10);
+constexpr byte R2C11 = keyIndex(2, 11);
+constexpr byte R2C12 = keyIndex(2, 12);
+constexpr byte R2C13 = keyIndex(2, 13);
+
+constexpr byte R3C0  = keyIndex(3, 0);
+constexpr byte R3C1  = keyIndex(3, 1);
+constexpr byte R3C2  = keyIndex(3, 2);
+constexpr byte R3C3  = keyIndex(3, 3);
+constexpr byte R3C4  = keyIndex(3, 4);
+constexpr byte R3C5  = keyIndex(3, 5);
+constexpr byte R3C6  = keyIndex(3, 6);
+constexpr byte R3C7  = keyIndex(3, 7);
+constexpr byte R3C8  = keyIndex(3, 8);
+constexpr byte R3C9  = keyIndex(3, 9);
+constexpr byte R3C10 = keyIndex(3, 10);
+constexpr byte R3C11 = keyIndex(3, 11);
+constexpr byte R3C12 = keyIndex(3, 12);
+constexpr byte R3C13 = keyIndex(3, 13);
+
+constexpr byte R4C0  = keyIndex(4, 0);
+constexpr byte R4C1  = keyIndex(4, 1);
+constexpr byte R4C2  = keyIndex(4, 2);
+constexpr byte R4C3  = keyIndex(4, 3);
+constexpr byte R4C4  = keyIndex(4, 4);
+constexpr byte R4C5  = keyIndex(4, 5);
+constexpr byte R4C6  = keyIndex(4, 6);
+constexpr byte R4C7  = keyIndex(4, 7);
+constexpr byte R4C8  = keyIndex(4, 8);
+constexpr byte R4C9  = keyIndex(4, 9);
+constexpr byte R4C10 = keyIndex(4, 10);
+constexpr byte R4C11 = keyIndex(4, 11);
+constexpr byte R4C12 = keyIndex(4, 12);
+constexpr byte R4C13 = keyIndex(4, 13);
+
+constexpr byte R5C0  = keyIndex(5, 0);
+constexpr byte R5C1  = keyIndex(5, 1);
+constexpr byte R5C2  = keyIndex(5, 2);
+constexpr byte R5C3  = keyIndex(5, 3);
+constexpr byte R5C4  = keyIndex(5, 4);
+constexpr byte R5C5  = keyIndex(5, 5);
+constexpr byte R5C6  = keyIndex(5, 6);
+constexpr byte R5C7  = keyIndex(5, 7);
+constexpr byte R5C8  = keyIndex(5, 8);
+constexpr byte R5C9  = keyIndex(5, 9);
+constexpr byte R5C10 = keyIndex(5, 10);
+constexpr byte R5C11 = keyIndex(5, 11);
+constexpr byte R5C12 = keyIndex(5, 12);
+constexpr byte R5C13 = keyIndex(5, 13);
+
 extern kaleidoscope::hardware::ErgoDox &ErgoDox;