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PWM and Shutters

Jim Mahaney
Prodigy 110 points
Other Parts Discussed in Thread: DLPC300, SN74AVC4T245

I put a probe on the TP12, TP13 and TP14 points, expecting to see a PWM signal, but instead just got 3.1V on TP12/TP14 and nothing on TP13.  Is this correct?  Also, does the light engine use shutters in front of the LED's and if so, is there a way to control them?

 

 

  • 0
    TI__Genius 9935 points

    Jim,

    The test points which you mention -- TP12, TP13, TP14 -- are JTAG pins. I don't know what you are trying to probe.

    The light engine does not use physical shutters in front of the LEDs. The LEDs are turned on/off, and current set, by the LED drivers. The LightCrafter GUI, and the API, provide software control of the LEDs (current, LED selection), although the operation of the LEDs during various video and pattern modes is controlled by the low-level sequence control provided by the DLPC300 to the LED drivers.

  • 0 in reply to Pascal DLP
    TI__Mastermind 30875 points

    Hi Jim,

    We had a bit confusion on the TPx point because both exisits on System and Driver board. I believe you are referring to Driver Board test points.

    Let us know how you are testing? With or without load connected... i.e., is the LED connected Also check the LED current settings, try changing them and let us know if it having any effect in the voltage reading at these TP s.

    Regards,

    Sanjeev

     

  • 0 in reply to Sanjeev
    Prodigy 110 points

    That may be the issue.  I did not realize they were on both boards.  I was trying to test the output of chip SN74AVC4T245 at location U6 which is part of the LED driver interface.  I did not see TP12, TP13 or TP14 on that card, where are they located?  I was testing with an analog scope while the projector was displaying a checkerboard pattern.

     

    Thanks,

    -Jim

  • 0 in reply to Jim Mahaney
    TI__Mastermind 30875 points

    Jim,

    You can refer to System Board schematics for TPx. It is shown on the pg #9 FPGA Interface.

    Did you try changing the LED current setting  and monitor the increase/decrease in the analog voltages at these points?

    Regards,

    Sanjeev