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I built the first iteration of the macropad project for a science fair in high school. The idea was to combine the dynamic interface design of touch displays with the positive tactility of traditional keyboard switches. This was accomplished by integrating small OLED displays into the top of each of the nine buttons on the macropad.

The device consists of two boards: the bottom board contains a microcontroller, 16 channel multiplexer, and logic level shifters. The top board breaks out the SPI bus and switch signals, with all signals routed through the ribbon cable connector. This connector makes disassembly and repair more convenient.

Fig. 2 Shows the wiring in layers on the two boards, and gives a general sense of the layout of the device.