OV9281 调试记录

一、基本概念

HTS = width_number_of_effective_cloumns+H_Blank，图像宽度+行消隐

VTS = height_number_of_effective_rows + V_Blank，图像高度+场消隐

OV9281 sensor array layout如下：

二、帧率配置

1、clock diagram

2、PLL configuration

XCLK:24MHz

PLL1 clock

0x030A[0]:0(default value),/1 24MHz

0x0300[2:0]:001(default value),/1.5 16MHz

0x0301[1:0],0x0302[7:0]:0x32(default value) 16MHzx50=800MHz

0x0303[3:0]:0000,/(1+0x0303[3:0]) 800MHz

0x0304[1:0]:11(default value),/8 100MHz

0x0305[1:0]:10(default value),/5 160Mhz

0x0306[0]:1(default value),/2 80MHz

MIPI_CLK=800MHz

PLL1 pix clk=100MHz

PLL1 pix clk=400MHz

PLL2 clock

0x0314[0]:0(default value),/1 24MHz

0x030B[2:0]:100(default value),/3 8MHz

0x030C[1:0],0x030D[7:0]:0x50(default value) 8MHzx80=640MHz

0x0313[3:0]:0001,/(1+0x0313[3:0]) 640MHz/2=320MHz

0x0312[3:0]:0111,/(1+0x0312[3:0]) 640MHz/8=80MHz

0x030F[3:0]:0011, /(1+0x030F[3:0]) 640MHz/4=160MHz

0x030E[2:0]:010,/2 160MHz/2=80MHz

PLL2 ADC clk=320MHz

PLL2 analog clk=80MHz

PLL2 sys clk=80MHz

datasheet配置参考：

3、HTS、VTS配置

HTS寄存器0x380C、0x380D，默认值0x02D8，实际值需要大于图像宽度+行消隐

VTS寄存器0x380E、0x380F，默认值0x038E，实际宽度需要大于图像高度+场消隐

4、FPS计算

计算公式：fps=sys_clk/(VTS*HTS)，PLL2 sys_clk为sys_clk

以sys_clk=80MHz，VTS=0x038E(910)，HTS=0x02D8(728)计算fps，fps=80000000/(910*728)=120.75

以sys_clk=80MHz，VTS=0x0E38(3640)，HTS=0x02D8(728)计算fps，fps=80000000/(3640*728)=30.18

4、改变帧率

一般是通过改变vts的值改变帧率，以下为君正sdk中ov9281驱动中改变帧率的函数，参数fps的值为运算之后的值，如帧率为30，fps=30<<16 | 1;

static int ov9281_set_fps(int fps)
{
    struct sensor_info *sensor_info = &ov9281_sensor_attr.sensor_info;
    unsigned int sclk = 0;
    unsigned short vts = 0;
    unsigned short hts = 0;
    unsigned int max_fps = 0;
    unsigned char tmp;
    unsigned int newformat = 0;
	unsigned short expo = 0;
    int ret = 0;

    sclk = OV9281_SCLK;
    max_fps = SENSOR_OUTPUT_MAX_FPS;

     /* the format of fps is 16/16. for example 25 << 16 | 2, the value is 25/2 fps. */
    newformat = (((fps >> 16) / (fps & 0xffff)) << 8) + ((((fps >> 16) % (fps & 0xffff)) << 8) / (fps & 0xffff));
    if(newformat > (max_fps << 8) || newformat < (SENSOR_OUTPUT_MIN_FPS << 8)){
        printf("ov9281 set fps warn: fps(%x) no in range\n", fps);
        return -1;
    }

    /* hts */
    ret = ov9281_read(sensor_i2c_dev, 0x380c, &tmp);
    hts = tmp << 8;
    ret += ov9281_read(sensor_i2c_dev, 0x380d, &tmp);
    if (ret < 0)
        return -1;

    hts |= tmp;

    /* vts */
    vts = sclk * (fps & 0xffff) / hts / ((fps & 0xffff0000) >> 16);
    ret = ov9281_write(sensor_i2c_dev, 0x380e, (unsigned char)(vts >> 8));
    ret += ov9281_write(sensor_i2c_dev, 0x380f, (unsigned char)(vts & 0xff));
    if (ret < 0)
        return -1;
	
    sensor_info->fps = fps;
    sensor_info->total_height = vts;
    sensor_info->max_integration_time = vts - 25;

    return 0;
}