无线图像（视频）传输系统ARM9+Atmega16+OV7620+nrf24l01（三）

OV7620支持的像素是：VGA(640*480)、QVGA(320*240)，我用的是QVGA模式(配合液晶屏显示)。使用OV7620关键还是正确配置其内部寄存器，还有就是SCCB数据传输协议的实现。

首先有必要说下OV7620所支持的图像格式，因为，我对图像这块不熟悉，这里只说明OV支持的几种输出格式，以及相关寄存器的配置。

RGB16/8 bit ,这些格式都不是真正的RGB数据流，而是Bayer矩阵，所以在终端显示时，必须将Bayer矩阵转换为RGB。转换的核心思想是通过插值算法将Bayer矩阵中的每个像素值(一个字节)转换为RGB三个字节(我不懂图像，只能说出方法，具体算法后面我会贴出)。

本次采用的是RGB raw16 bit 模式，由于OV7620只引出了Y通道，所以配置为one line mode(这里出现了问题，明明RGB三个分量都有，但是通过插值后显示出来的尽然还是灰度图像，后面再分析原因)。下面贴出OV7620相关寄存器的配置：

unsigned char reg_12_w_reset[2]={0x12,0x80};//先清零

unsigned char reg_11_w[2]={0x11,0x00}; //配置PCLK速率 PCLK=(CLK_input/(CLK<5:0>+1)*2)),本次为1/2时钟频率

unsigned char reg_12_w[2]={0x12,0x2c}; //使能AGC，选择raw data outtput,并且使能自动白平衡

unsigned char reg_14_w[2]={0x14,0x24};//QVGA digital output format ,RGB gamma on

unsigned char reg_28_w[2]={0x28,0xa0}; //one-line RGB data format ,select Progressive scan mode

下面是Bayer转RGB24的算法(在液晶屏上显示时还要转为RGB16):

void bayer2rgb24(unsigned char *dst, unsigned char *src, long WIDTH, long HEIGHT)

{

long int i;

unsigned char *rawpt, *scanpt;

long int size;

rawpt = src;

scanpt = dst;

size = WIDTH*HEIGHT;

for ( i = 0; i < size; i++ )

{

if ( (i/WIDTH) % 2 == 0 ) //奇数行

{

if ( (i % 2) == 0 ) //奇数列

{

/* B */

if ( (i > WIDTH) && ((i % WIDTH) > 0) )

{

*scanpt++ = ((long int)*(rawpt-WIDTH-1)+(long int)*(rawpt-WIDTH+1)+

(long int)*(rawpt+WIDTH-1)+(long int)*(rawpt+WIDTH+1))/4; /* R */

*scanpt++ = ((long int)*(rawpt-1)+(long int)*(rawpt+1)+

(long int)*(rawpt+WIDTH)+(long int)*(rawpt-WIDTH))/4; /* G */

*scanpt++ = *rawpt; /* B */

}

else /* first line or left column */

{

*scanpt++ = *(rawpt+WIDTH+1); /* R */

*scanpt++ = ((long int)*(rawpt+1)+(long int)*(rawpt+WIDTH))/2; /* G */

*scanpt++ = *rawpt; /* B */

}

}

else

{

/* (B)G */

if ( (i > WIDTH) && ((i % WIDTH) < (WIDTH-1)) )

{

*scanpt++ = ((long int)*(rawpt+WIDTH)+(long int)*(rawpt-WIDTH))/2; /* R */

*scanpt++ = *rawpt; /* G */

*scanpt++ = ((long int)*(rawpt-1)+(long int)*(rawpt+1))/2; /* B */

}

else /* first line or right column */

{

*scanpt++ = *(rawpt+WIDTH); /* R */

*scanpt++ = *rawpt; /* G */

*scanpt++ = *(rawpt-1); /* B */

}

}

}

else //偶数行

{

if ( (i % 2) == 0 ) //奇数列

{

/* G(R) */

if ( (i < (WIDTH*(HEIGHT-1))) && ((i % WIDTH) > 0) )

{

*scanpt++ = ((long int)*(rawpt-1)+(long int)*(rawpt+1))/2; /* R */

*scanpt++ = *rawpt; /* G */

*scanpt++ = ((long int)*(rawpt+WIDTH)+(long int)*(rawpt-WIDTH))/2; /* B */

}

else

{

/* bottom line or left column */

*scanpt++ = *(rawpt+1); /* R */

*scanpt++ = *rawpt; /* G */

*scanpt++ = *(rawpt-WIDTH); /* B */

}

}

else

{

/* R */

if ( i < (WIDTH*(HEIGHT-1)) && ((i % WIDTH) < (WIDTH-1)) )

{

*scanpt++ = *rawpt; /* R */

*scanpt++ = ((long int)*(rawpt-1)+(long int)*(rawpt+1)+

(long int)*(rawpt-WIDTH)+(long int)*(rawpt+WIDTH))/4; /* G */

*scanpt++ = ((long int)*(rawpt-WIDTH-1)+(long int)*(rawpt-WIDTH+1)+

(long int)*(rawpt+WIDTH-1)+(long int)*(rawpt+WIDTH+1))/4; /* B */

} else {

/* bottom line or right column */

*scanpt++ = *rawpt; /* R */

*scanpt++ = ((long int)*(rawpt-1)+(long int)*(rawpt-WIDTH))/2; /* G */

*scanpt++ = *(rawpt-WIDTH-1); /* B */

}

}

}

rawpt++;

}

}