This is an alternative to one of my other projects on PCBWAY, the wireless Kempston joystick interface for the ZX Spectrum. This RX board can be used with the RF joystick TX board here on PCBWAY, but the output is via a joystick connector (eg ATARI 9 pin D-Type). This gives wireless functionality to any computer or games console that uses switched joysticks.

Please note: The reed switch part number on the underside of the PCB is incorrect. The correct part is: Meder SIL05-1A72-71D. The BOM text file is now correct.

The RX LED should flicker during normal operation. Each flash indicates that a packet has been received and decoded successfully. The received single data byte contains flags giving the status of joystick UP, DOWN, LEFT, RIGHT & FIRE. The status of each of these flags is then used to switch the state of an output pin, which in turn drives the base of a transistor used to switch the corresponding reed relay. One switch contact of each relay is connected to joystick common, and the other is connected to the appropriate joystick connection.

The coil of the reed relays is around 500R, therefore the current for each energised coil is only around 10mA @ 5V, so the ATMEGA328 could easily drive the relays directly. A maximum of 3 relays could be energised at one time (UP, LEFT & FIRE for example), so total current would be around 30mA, but I opted to switch them by transistor in order to allow for different relays to be used which may have lower coil resistances. The relay used has a built in flywheel diode across the coil, if a relay is used without one, a diode (1N4148) should be soldered across the coil pins in the orientation shown on the top silk of the PCB.

The board is powered by a Li-on PP3. Maximum current is around 45mA.