Matrices and Duplex Matrix Improving upon their design. Maximizing the matrix For non-macropad keyboards, routing a matrix with one pin per row and column will almost always lead to inefficient results. With the same number of keys, a more "square" matrix will require less cols and rows total than a more "rectangular" one. I.E. For 30 keys, 5x6 is 11 pins, while 2x15 is 17 pins. The Duplex Matrix Each "column" spans two physical columns. Two "rows" exist for each physical row. See schematic at bottom for a routing example. Pros Fit more keys for rectangular keyboards using less pins More pins to use for fancy features Use cheaper controllers to reduce the final product cost Cons More complicated to wire Can be more difficult to add more keys to the matrix later on Harder to follow on a schematic