Spectrum Adapter Using PC-Keyboard

The adapter project provides the possibility of connecting to expansion bus like the joystick adapters, in order to connect a standard AT or PS/2 type of keyboard and work with the Spectrum.

A PIC16F84 microcontroller is the heart of the adapter, which should be programmed before being inserted on the board. There are two flat cables inside the Spectrum with 8 and 5 contacts which are part of bottom of keyboard where a matrix of rubber keys is found. 8 half-rows with 5 keys each, divides the matrix.

The keyboard is part of inner hardware in the Spectrum but the PC-keyboard is independent of the host since it only uses 4-wire cable for communication. The controller functions as the host and the communication between the PC and keyboard are done using a 5-pin DIN connector or using a 6-pin PS/2 connector. One wire is the clock signal in both cases while another wire is the data and the other two wire are for +5V power supply and GND.

The PIC16F84 is made of a microprocessor, 1Kbyte flash EEPROM memory, 68 bytes internal RAM memory, and 13 I/O ports. A heatsink is used for LM7805.

Rest of the project