無線圖像（視頻）傳輸系統(tǒng)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(配合液晶屏顯示)。使用OV7620關(guān)鍵還是正確配置其內(nèi)部寄存器，還有就是SCCB數(shù)據(jù)傳輸協(xié)議的實(shí)現(xiàn)。
首先有必要說下OV7620所支持的圖像格式，因?yàn)?，我?duì)圖像這塊不熟悉，這里只說明OV支持的幾種輸出格式，以及相關(guān)寄存器的配置。
RGB16/8 bit ,這些格式都不是真正的RGB數(shù)據(jù)流，而是Bayer矩陣，所以在終端顯示時(shí)，必須將Bayer矩陣轉(zhuǎn)換為RGB。轉(zhuǎn)換的核心思想是通過插值算法將Bayer矩陣中的每個(gè)像素值(一個(gè)字節(jié))轉(zhuǎn)換為RGB三個(gè)字節(jié)(我不懂圖像，只能說出方法，具體算法后面我會(huì)貼出)。
本次采用的是RGB raw16 bit 模式，由于OV7620只引出了Y通道，所以配置為one line mode(這里出現(xiàn)了問題，明明RGB三個(gè)分量都有，但是通過插值后顯示出來的盡然還是灰度圖像，后面再分析原因)。下面貼出OV7620相關(guān)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)),本次為1/2時(shí)鐘頻率
unsigned char reg_12_w[2]={0x12,0x2c}; //使能AGC，選擇raw data outtput,并且使能自動(dòng)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轉(zhuǎn)RGB24的算法(在液晶屏上顯示時(shí)還要轉(zhuǎn)為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 ) //奇數(shù)行
{
if ( (i % 2) == 0 ) //奇數(shù)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 //偶數(shù)行
{
if ( (i % 2) == 0 ) //奇數(shù)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++;
}
}
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