Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State Resolved
  • Locked Locked
  • Replies 11 replies
  • Subscribers 28 subscribers
  • Views 2679 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Pattern Exposure Time and Frame Period

Nobuyoshi Arai44
Expert 2575 points
Other Parts Discussed in Thread: DLPC350

Hello ALC team,

 

I have a question about the Pattern Exposure Time and Frame Period(Pattern Period).

 

Our customer is considering to use Pattern sequence mode with video port. Color depth is 8bt and output frame rate is 120 fps.

In this case, we would like to know what is the minimum value of Pattern Exposure Time and Frame Period.

 

If we set Pattern exposure is 8102 us and Pattern period is 8333 us, we can send the pattern sequence but validate sequence command is failed.

 

It seems the specification is the Pattern Exposure = Pattern period or Pattern Exposure - Pattern period > 230us.

So, we think the above settings meet the specification. Would you please tell us the reason why the validate command is failed?

 

If we set 8333us for both Pattern Exposure Time and Frame Period, it seems working correctly.

Is this the minimum settings for 120fps?  If same values are set, is there any restriction or limitation for the working?

 

It would be helpful if you can give any comment on this.

 

Best Regards,

Nobu Arai

  • 0
    TI__Mastermind 30875 points
    Hi Nobu Arai,

    For the Pattern Mode with Video Port ; it is mandatory to set both Pattern Exposure and Frame Period equal; for 120Hz it is 8333us. And the actual VYSNC period must be set >= the Pattern Exposure period.

    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Expert 2575 points
    Hello Sanjeev-san,

    Thank you for the answer.

    Please let me confirm your answer.

    >> For the Pattern Mode with Video Port ; it is mandatory to set both Pattern Exposure and Frame Period equal; for 120Hz it is 8333us.

    Q1:
    For the pattern sequence mode with Video port, do they have to set same values for both Pattern Exposure and Frame Period?
    It seems the specification is the Pattern Exposure = Pattern period or Pattern Exposure - Pattern period > 230us.
    Do you mean that they cannot use the value of “Pattern Exposure - Pattern period > 230us” ?
    In our experiment of LightCrafter4500, it seems we can validate the working like below.
    Exposure time : Frame Period = 8333 : 8564 > 230
    　　　　　　　　　　 8334 : 8564 > 230
    Please tell us which is correct, they have to set same values or they can set interval more than 231us.


    Q2:
    I also would like to know the minimum value of exposure and frame period in the case of 120Hz.
    In our experiment of LightCrafter4500, it seems we can validate the working like below.

    Exposure time : Frame Period = 8333 : 8333 -> Good
    　　　　　　　　　　8330 : 8330 -> Good
    　　　　　　　　　　8300 : 8300 -> Good
    　　　　　　　　　　8200 : 8200 -> Fail (Exposure/Period OOR in Validate command)

    It seems 8300us of exposure and frame period can work in LightCrafter4500.
    Would you please tell us what is the specification of minimum value of Exposure time of DLPC350?

    Best Regards,
    Arai
  • 0 in reply to Nobuyoshi Arai44
    TI__Mastermind 30875 points

    Q1: For Trigger Mode 0, yes, you must always keep the Pattern Exposure = Pattern period. Keeping the Pattern Exposure - Pattern period > 230us doesn't work. Please set the same values

    Q2: As per the datasheet specification 8333us is minimum for 8-bit display; there is slight margin the absolute minimum is 8265us.

    Regards,
    Sanjeev

  • 0 in reply to Sanjeev
    Expert 2575 points

    Hello Sanjeev-san,

    Thank you for the answer. I understood we must set the same values. 

    Please let me ask you an additional question about the specification.

     

     

    When we set 8333us to both Exposure time and Frame period in case of Trigger mode0, what is the value of the period that TRIG_OUT_1 is low?

     

    As I checked it with the Lightcrafter4500, it looks it is about 20 us. But our customer wants to the specification of this period.

     

    It would be helpful if you can give this information.

     

    Best Regards,

    Nobu Arai

  • 0 in reply to Nobuyoshi Arai44
    TI__Mastermind 30875 points
    Hi Nobu-san,

    I don't follow your question properly.

    TRIG_OUT_1 precisely follows the pattern exposure time. User has option to set delay for the signal between -20.05 us to +2.787us also to adjust the polarity to Active LOW or Active High.

    Can you show in the timing diagram which 20us you are referring to ?

    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Expert 2575 points
    Hello Sanjeev-san,

    I am sorry for making you confused.
    Please let me explain again.

    Our customer is using the pattern sequence mode with video port input from external MPU (Trigger mode0).
    The image is input to Video port with 60Hz and a pattern sequence is just one that 8bit Green and 8bit red are exposure in order by 120hz, then it is repeated.
    So, they are setting 8333us to the exposure time and frame period.

    In this case, we want to know the period of LOW state of TRIG_OUT1 between 1st exposure time and 2nd exposure time.
    I checked it with LCr4500 and it was 20us. I would like to know the actual specification of the LOW state period between 1st and 2nd exposure in the case of 8333us frame and exposure period settings. They want to use this trigger signal and want to know the minimum period of time so that they can catch this trigger signal.

    Please let me know if you still do not understand my question.

    Best Regards,
    Nobu Arai
  • 0 in reply to Nobuyoshi Arai44
    TI__Mastermind 30875 points
    Hi Nobu-san,

    20us is the minimum time.

    Incase you need more time, you can simply select 'Clear DMD after exposure' i.e., refer to Programmer's guide Table 2-68. Pattern Display LUT Data - Pattern Definition Command; BYTE#2 BIT1 = '1' Insert black-fill pattern. This will add 230us gap from 20us gap.

    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Expert 2575 points

    Sanjeev-san,

     

    I am sorry again but please let me confirm one more question.

     

    If the pattern sequence is just one that Red 8bits and Green 8bits are exposure at 8333us period like the attached file.

    In this case, what is the actual LED ON/OFF period?

    Would you please tell us which case is correct or other?

     

    1）LED ON：8333uS -> LED OFF 20uS -> LED ON：8333uS

    2）LED ON：8333uS -> LED OFF 20uS -> LED ON：8333uS -> LED OFF：20uS

    3）LED ON：8313uS -> LED OFF 20uS -> LED ON：8313uS

    4）LED ON：8313uS -> LED OFF 20uS -> LED ON：8313uS -> LED OFF：20uS

     

    Best Regards,

    Nobu Arai

  • 0 in reply to Nobuyoshi Arai44
    TI__Mastermind 30875 points
    Option #1. We recommend selecting the 'Clear DMD after exposure' for the last pattern; this will make sure after displaying the G0-G7 the LED enable signals are disabled and the data on the DMD is cleared after the exposure time.

    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Expert 2575 points
    Sanjeev-san,

    Thank you for the answer.

    I understood that the 'Clear DMD after exposure' setting is recommended.
    But we would like to know the actual period of LED (exposure) ON/OFF in this setting.
    Is it possible to tell us the expected timing?

    It looks the TRIG_OUT_1 signal is like below as I checked on the LCr4500;
    TRIG_OUT_1 High：8313us -> Lo 20us -> High：8313us -> Lo：20us

    Is LED (Exposure) ON/OFF timing same or not?
    LED ON：8313us -> LED OFF 20us -> LED ON：8313us -> LED OFF：20us
    or
    LED ON：8313us -> LED OFF 20us -> LED ON：8103us -> LED OFF：230us

    It would be appreciated your comment.

    Best Regards,
    Nobu Arai
  • 0 in reply to Nobuyoshi Arai44
    TI__Mastermind 30875 points
    Hi Nobu-san,

    After looking into the actual display sequence behavior.

    first, 20us gap b/w the patterns is expected.

    This is expected output LED ON：8313us -> LED OFF 20us -> LED ON：8313us -> LED OFF：20us

    Regards,
    Sanjeev