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The history of the split prefetch code: Once up on a time, I thought that it was important to stay very close to the "official" pixel clock. We could do this when copying 32 bit words from cache to the GPIO set/clear registers, but not when shifting 8 bit values as we do now. One problem with 32 bit values is that transferring that amount of data exceeds the time available in the hsync pulse. Hence the idea to split the prefetch between hsync pulse and horizontal front porch. Note that we also split prefetches between the two VGA lines of each QVGA line. This commit does not change that mechanism. - ubb-vga.c (line, frame): removed code fragments for prefetch split between hsync pulse and front porch - ubb-vga.c (line, frame): remove code fragments for measuring time relative to the rising edge of hsync (and letting the prefetch time control the hsync length), not the falling edge
Ben Blinkenlights ================= This project is a proof of concept implementation of Rikard Lindstrom's idea of using the Ben's 8:10 card slot as a general extension interface also for devices that don't speak MMC or SD/SDIO. The application is a simple LED circuit, as suggested by David Samblas. The 8:10 card slot gives access to six GPIOs, a 3.3 V supply that can be switched on and off by software, and ground. We use a simple form of multiplexing to drive ten LEDs with this interface. Note that one should only light one LED at a time. If multiple LEDs are lit, they will share the current though the common resistor, and will thus be less bright than a single LED.