demosaic3.0

应该写一个vga_data模块，用来从rom读取给vga_driver的数据

因为以后的流水线操作涉及到读取ram缓存条的图像数据，先解决从rom读图片，接下来再解决从sd和ram读图片

查看该芯片的rom

5,140 Kbits embedded memory

640*480的RGB888图像是900k

板子上的SD卡是连ARM的，就很蛋疼

要求规格如下（因为该SD卡也可以用来boot linux）

SD協會定義了四種速度規格，協助使用者更輕易的區分不同SD卡的傳輸速率。此四種規格指讀寫速率至少必須符合的標準 ( Class 2: 2 MB/s; Class 4: 4 MB/s; Class 6: 6 MB/s; Class 10: 10 MB/s )

TF卡即是T-Flash卡，又叫micro SD卡

将图片转成mif

设置rom ip核，图像深度为25万rom的ip核设成3w深度

突然发现原来640480的vga不够用了，改成12801024。修改PLL输出时钟和vga的一些模块参数和位宽即可

测试后正常

等下全部改clk_25

编译报错说rom ip核太小

Error (170040): Can’t place all RAM cells in design

Info (170034): Selected device has 553 memory locations of type M10K block. The current design requires 744 memory locations of type M10K block to successfully fit.

Info (170033): Memory usage required for the design in the current device: 135% M10K block memory block locations required

Info (170043): The Fitter setting for Equivalent RAM and MLAB Paused Read Capabilities is currently set to Care. More RAMs may be placed in MLAB locations if a different paused read behaviour is allowed.

把图片改成100*100的，然后图片的存储另做考虑

显示正常

fpga可以倍频

vh-vv的直方图

wh的直方图

matlabs是四位小数，

查sigmod函数在FPGA上实现（感觉非线性在FPGA上的实现一直是个有意思的话题）

这个函数全称是Log-sigmoid function, also known as a logistic function,

关键词是FPGA，Non-linear Approximation ，Symmetric Table Lookup Addition Method（STAM）
Taylor series expansion
the look-up tables
CORDIC(Coordinated Rotation Digital Computer)
分段然后用一次，二次多项式拟合：A Non-linear Approximation of the Sigmoid Function based on FPGA