This project is based on ideas from Rickard's electronic projects page and David B. Thomas VCR Pong. However, I have developed the simplicity even further, eliminating most of the external components. Using microcontrollers with internal 4MHz clock generator there is no need for the xtal. The 12f675 part also operates on wide voltage range, and the regulator can be removed.
For game controller, I plan on using the old Commodore 64 style paddless. They include firing buttons, which I plan on using as power switch and game reset. 16F675 has a low power sleep mode with 1nA current consumption, so I plan on using that to switch off.
I think this schematic diagram tells you all. Note that the power to paddle resistors comes from an output pin, so that current can be switched off also in sleep state.
Prototype board still has redundancy, but is already quite impressive for a 'video game system'.
1x PIC12F675 1x 100 nF 1x 100 kohm 2x 10 kohm 1x 220 ohm 1x 560 ohm 1x 9P male D-connector for Commodore 64 paddles 1x RCA female for video output 1x 2xAA or 2xAAA battery case
The prototype has power consumption of 0.5 mA running with the video cable disconnected from the TV set, and 4.5 mA when the cable is connected. So most of the power goes to drive the 75 ohm video line. These measurements were made with two AA cells giving about 2.9 V for the circuit. The paddles of course also consume some power.
At the moment the game software is still under design. Only a simple PAL 625 line test image video output program exists. It compiles with gpasm / gplink.
Download the program source here: pong_675.asm, or hex file here: pong_675.hex