This is the RF receiver and Kempston joystick interface board for the wireless joystick project for the Sinclair ZX Spectrum. The RF ASK receiver module used here is a RWS-371, though other versions of the same thing do exist. The board receives a data packet from the transmitter roughly 14 times a second. The RX LED flashes briefly every time a packet is received and decoded. The payload is one byte of data which defines the current state of the joystick UP, DOWN, LEFT, RIGHT & FIRE actions. This byte is decoded and put onto the Spectrum data bus (in the order defined by the Kempston standard) via a Tri-State buffer (74HC540). The output of the Tri-State buffer is controlled by an address decoder (74HC32).

Please note: Unused inputs of the buffer have individual 10k pullup resistors for possible future use. Also, the buffer has inverting outputs so the outputs at the Atmega328 are active LOW (hence the pullups rather than pulldown resistors).

You will need the RadioHead Arduino library by Mike McCauley to compile the code. It's easy enough to find with a Google search.