实现用SDRAM运行nios，同时用SRAM保存摄像头数据，关于神经网络控制，该函数用来计算任意函数的一阶偏导数(数值方法)。- Implemented with SDRAM run nios, while saving camera data SRAM, On neural network control, This function is used to calculate the arbitrary function of the first order partial derivative (numerical methods).