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DLPC910: what is going to happen when DLPC is in idle

Part Number: DLPC910
  • Hi 

    I am concerned the content in 8.5.3 of DLPC910 datasheet as shown below

    "Disabling the watchdog is not recommended unless the user
    ensures that a mirror clocking pulse to the entire DMD occurs within 10 seconds.

    During the time when the DLPC910 is in idle mode or is not operating, it is recommended to exercise the DMD mirrors by continuously loading
    an alternating all on all off patterns."

    if watchdog is enable but our FPGA (Xilinx Kintex Ultra) doesn't "exercise the DMD mirrors by continuously loading an alternating all on all off patterns."  

    then what is going to happen in DLPC910 or DMD module after DLPC910 being in idle for certain time ?

     

    Why I ask this question is because I observed image overlap constantly on DMD when I do bitmap display as following sequence.

    execute dmd reset and wait for done of dmd training 

    display bitmap A on DMD            <- everything is OK (repeat bitmap display quickly)

    display bitmap A on DMD            <- everything is OK (repeat bitmap display quickly)

    .........

    display bitmap A on DMD            <- everything is OK (repeat bitmap display quickly)

    wait about 1 min                          <- DLPC910 is in idle, FPGA does not exercise the DMD mirrors 

    display bitmap B on DMD            <- Here, I observe image overlap

    Looks like image overlay on DMD is related to DLPC910's idle....

    "exercise the DMD mirrors by continuously loading an alternating all on all off patterns." is a MUST to do by FPGA?

    Thank you very much!

    Zan

  • Hello Zan,

    If you have the watchdog timer enabled it will periodically (about every 6-8 seconds) will send a Global Micromirror Clocking Pulse [MCP] (micromirror reset) to the DMD.  This will not cause the micromirrors to change state if no new data has been loaded, but will cause them to come up from their landed position but return to the same state.  This keeps the micromirrors exercised.

    The reason it is recommended to alternate between all on / off is that this is the most robust method of exercising the mirrors to ensure reliable operation of the micromirrors. 

    Can you explain further what you mean when you say "wait about 1 min  <- DLPC910 is in idle"? 

    • Do you mean that the image is on the DMD but no new data is being loaded?
    • Or do you mean that a mirror float has been applied?

    Then after that you display bitmap B on the DMD.  Please verify that this means you are loading new data and then sending a request for an MCP.  

    Please try sending a request for an MCP just before loading the bitmap B data and then request another MCP.  If you are waiting a minute before loading the data, it is possible that you are sending data in the middle of a Watchdog MCP.  Requesting an MCP just before loading bitmap B data will reset the Watchdog timer so that you do not risk loading data in the middle of a Watchdog triggered MCP.

    If you are actively using patterning, then this is not what we refer to as "idle".  Even if it is the same pattern.  However, I would recommend sending an MCP request every second or so rather than rely on the Watchdog timer to trigger an MCP request.

    Please let me know the result.

    Fizix

  • Hi Fizix,

    About your question "Then after that you display bitmap B on the DMD. Please verify that this means you are loading new data and then sending a request for an MCP. "

    Yes. we always send a request for an MCP after finish new data loading.


    About your question "Can you explain further what you mean when you say "wait about 1 min <- DLPC910 is in idle"? "

    "wait about 1 min" means, after we finish previous image load with MCP, no new data is being loaded and no other action like mirror float or MCP is being applied?


    I agree with your hypothesis that it is possible "send data in the middle of a Watchdog MCP".

    Next, I am going to try to send a MCP request before loading bitmap B.

    Thank you very much for your replying.

    Best,
    Zan