atmega16 实现闹钟，使用矩阵键盘，算法采用死循环-the atmega16 achieve alarm clock, the use of the keyboard matrix, the algorithm uses the infinite loop

用于四轴飞行器的姿态算法，内含各种矩阵加减乘转置、求逆等运算，及姿态kalman滤波算法，可适用于低速旋翼机的姿态导航-For four-axis spacecraft attitude algorithm, containing a variety of matrix addition and subtraction to multiply the transpose and inverse operations, and attitude Kalman filtering algorithm