The I2C programmable keyboard was developped as part of project "RPN programmable calculator". However, this keyboard is usable for many other application. With I2C interface can be connected to most of microcontrollers today. The keys are organized in 8x8 matrix + 1 key. The key's columns and rows are available on the connector and can be connected to vintage microprocessors like Z80A. The matrix key is scanned by slave I2C MCU. The MCU debounces and maintains a FIFO of keys-press events, including autorepeat, if this feature is enabled. An Interrupt output can be configured to alert key press either as they occur, or at maximum rate.
The MCU includes a tone generator to generate automatic key-click sounds or alarm tones under processor control. The sounder frequencies cover the 5^th musical octave (523.25 Hz to 987.77 Hz), plus seven other musical notes up to 2637 Hz. The output can also be programmed to be high or low for the sound duration to operate an electonic sounder, relay or lamp. The 16-digits LED display are 0.28" high, common cathode, multiplexed in two 8-digits group. The display can be easy interfaced to any MCU or to Maxim MAX7219 or 7221 display controller.

On the keyboard are 8-bit Microchip GPIO controller with I2C interface and 8 LED diodes.

The programmable keyboard is powered from +3.3V (2.7V ... 3.6V). Board size is 7.3" x 3.8" (186 x 96mm).

Documentation

• user and programming manual (pdf), sofware examples for Microchip PIC MCU and 4D displays

Interface

The keyboard has two possible interfaces, either parallel via seven 8-bit ports or a serial I2C interface. In case of I2C interface, the display can be connected via two MAX7219 display drives.