The glue logic for your Arduino project can take its time. Sometimes though, the rise time of a logic transition is important. The application that prompted this article was the measurement of ...

// Some model of cheap Yellow display works only at 40Mhz // #define DISPLAY_SPI_SPEED 40000000L // 40MHz #define DISPLAY_SPI_SPEED 80000000L // 80MHz #define SD_SPI_SPEED 80000000L // 80Mhz ...