TDA4AL-Q1: IMX728 exposure sensor setting problem

Hi YL,

Please don't not share any confidential information on public forum.

yl chen said:

we find the exposure has blink, when the sensor gain have changing.

Could you please provide some more details?

yl chen said:

how to produce the gain table such as imx728_gain_table.h.

The table is basically for converting linear gain value from AE to IMX728 sensor register format (typically in dB format).

Hi, Gang,

Gang Hua said:

The table is basically for converting linear gain value from AE to IMX728 sensor register format (typically in dB format).

So, Does I needs to find the converting gain table myself?

If yes, how do I to find this, is it any method to measure linear gain table?

If no, where do I find this table, does it provide by Sony?

Thanks,

YL

Hi YL,

yl chen said:

So, Does I needs to find the converting gain table myself?

There is a sample gain table for IMX728 in SDK code base.

https://git.ti.com/cgit/processor-sdk/imaging/tree/sensor_drv/src/imx728/imx728_gain_table.h?h=main

The 1st column is the linear gain value output from AE.
The 2nd is the corresponding Sony sensor register value.

yl chen said:

If no, where do I find this table, does it provide by Sony?

Sony would definitely be able to help you with any questions about the sensor gain values.
They helped us creating the table in the above link.

Hi, Gang,

Thanks your reply.

Another question, what do I know the linear gain value from platform corresponding to the sensor db value.

For a example, 1036 is 0.1 db, 1136 is 0.9 db, which setting on FME_ISPGAIN_UNIT is 0.1 db base.

static const uint32_t gIMX728GainsTable[ISS_IMX728_GAIN_TBL_SIZE][2U] =
{
    {1024, 0x0}, \
    {1036, 0x1}, \
    {1048, 0x2}, \
    {1060, 0x3}, \
    {1072, 0x4}, \
    {1085, 0x5}, \
    {1097, 0x6}, \
    {1110, 0x7}, \
    {1123, 0x8}, \
    {1136, 0x9}, \
    {1149, 0xA}, \

Thanks,

YL

yl chen said:

For a example, 1036 is 0.1 db, 1136 is 0.9 db, which setting on FME_ISPGAIN_UNIT is 0.1 db base.

Yes, that is correct.

yl chen said:

Another question, what do I know the linear gain value from platform corresponding to the sensor db value.

What is your question?

Hi, Gang,

I means how to I know 1036 is respect to 0.1 db.

How's 1036 to calculate on TI platform definition.

Thanks,

YL

Hi, Gang,

Thanks your clarify explanation.

Another a question, that make me confused.

In iss_sensors.h on imaging\sensor_drv\include.

/**
 *  \brief Sensor Specific Auto Exposure Dynamic Parameters
 * \ingroup group_vision_function_imaging_sensordrv
 */
typedef struct {
    IssAeRange exposureTimeRange[MAX_AE_DYN_PARAMS];
    /**< range of exposure time in nanoseconds */
    IssAeRange analogGainRange[MAX_AE_DYN_PARAMS];
    /**< range of sensor gain, 1024 = 1x */
    IssAeRange digitalGainRange[MAX_AE_DYN_PARAMS];
    /**< range of ISP Digital gain, 256 = 1x */
    uint32_t                     numAeDynParams;
    /**< Number of Valid Entries in above arrays */
    IssAeRange targetBrightnessRange;
    /**< range of target brightness */
    uint32_t                     targetBrightness;
    /**< target brightness value */
    uint32_t                     threshold;
    /**< threshold for not using history brightness information */
    uint32_t                     exposureTimeStepSize;
    /**< step size of exposure time adjustment */
    uint32_t                     enableBlc;
    /**< TRUE enables Backlight compensation, disabled otherwise */
} IssAeDynamicPara

Could you help to confirm which exposure time unit does correct?

In define of exposureTimeRange, the unit annotation is nanoseconds.

IssAeRange exposureTimeRange[MAX_AE_DYN_PARAMS];
/**< range of exposure time in nanoseconds */

But I see the FAQ on https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1262114/faq-setting-up-auto-exposure-ae-for-your-image-sensor-with-tda4-am6xa-isp-vpac

The exposureTimeRange unit is microseconds.

Note: the exposureTimeRange use nanoseconds in iss_sensor_imx728.c on imaging\sensor_drv\src\imx728

static int32_t IMX728_GetExpPrgFxn(uint32_t chId,
                                    void *pSensorHdl,
                                    IssAeDynamicParams *p_ae_dynPrms)
{
    int32_t status = 0;
    uint8_t count = 0;

    p_ae_dynPrms->targetBrightnessRange.min = 40;
    p_ae_dynPrms->targetBrightnessRange.max = 50;
    p_ae_dynPrms->targetBrightness = 45;
    p_ae_dynPrms->threshold = 1;
    p_ae_dynPrms->enableBlc = 1;

    p_ae_dynPrms->exposureTimeStepSize         = 1000000;  // nsec
    p_ae_dynPrms->exposureTimeRange[count].min = 10000000; // nsec
    p_ae_dynPrms->exposureTimeRange[count].max = 10000000; // nsec
    p_ae_dynPrms->analogGainRange[count].min   = 1024;
    p_ae_dynPrms->analogGainRange[count].max   = 16229;
    p_ae_dynPrms->digitalGainRange[count].min  = 256;
    p_ae_dynPrms->digitalGainRange[count].max  = 256;
    count++;

    p_ae_dynPrms->numAeDynParams = count;
    return (status);
}

Thanks,

YL

Hi YL,

yl chen said:

Could you help to confirm which exposure time unit does correct?

As a convention we typically to use "us" (microsenconds) for AE settings.
But, there is no unit in the source code (just number).
So as long as the AE settings and the sensor driver are aligned, using ns (or anything else) is fine too.