med into the OSD.РNTSC Sampling?The OSD outputs NTSC horizontal and vertical sync pulses as their own signals. We triggered interrupts on those and then counted cycles to correctly down-sample NTSC frames line by line, reading a frame into a 39x60 8-bit array.РFiltering?Our sampling timing (and therefore spatial accuracy) couldn’t be perfect, so we used a moving average filter on our output to reduce temporal flicker.РProgram Flow?Our main loop executes based on the NTSC frame rate. Several state machines control the main menu and games. All the game logic is based off a millisecond time base provided by the MCU’s 16-bit hardware timer.РPrinted Circuit Board (PCB)РWe would like to thank Atmel, Maxim-IC, and Texas Instruments for all their hardware donations that made this project possible.
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