• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 47 subscribers
  • Views 649 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.

Rare issue with THS8200

Ronak Desai
Intellectual 545 points
Other Parts Discussed in Thread: THS8200

Hi,

We have used THS8200 in our custom board design and we are facing a strange and very rare issue. In our design DM8148 DVO2 output is provided to THS8200. We are using standard driver provided with DVR-RDK-4.1 to configure THS8200. We are successfully able to configure it for almost 15 resolutions and everything works.


We have developed 250 board but on 9-10 board we are facing strange issue. With same binaries we are observing that on these boards no output comes from THS8200. We don't see any activity on R, G and B lines also we are not seeing Vertical Sync signal and only Horizontal Sync signal is available but with wrong frequency.

We have measured the sync frequencies and pixel clock frequency at the input side of THS8200 which is output of DM8148 and all these signals are OK with respective frequencies.

We are puzzled that where is the problem because on ~240 board everything is working. Chip assembly seems OK as per our observation.

Can anyone suggest where we should look into to solve this problem?

Thanks,

Ronak

  • 0
    TI__Mastermind 43875 points

    Are you passing the H & V syncs through the THS8200 or bypassing the THS8200?

    Check that all the signals going to the THS8200 are wiggling as expected, i.e. PClk is at the correct frequency, H & V from the processor are good, all data lines are wiggling.

    Check the signal integrity of the I2C signals going to the THS8200 (measure then at the THS8200)

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Intellectual 545 points

    Hi Steve,


    Thanks for the reply.


    We are providing H & V syncs through THS8200. Also, we have checked output signals of processor  i.e. Pclk, H & V sync on oscilloscope and everything are accurate and having proper frequency.

    We could read-write the THS8200 registers via i2c all the time so registers are also configured properly.


    -Ronak

  • 0 in reply to Ronak Desai
    TI__Mastermind 43875 points

    Check all your power supplies are at the correct levels and clean.

    Power supplies should be measured with both the ground and tip connections on the THS8200 pins and preferably with a differential probe. Enable persistence on the scope and monitor the noise levels over a few 10s of seconds to make sure you are capturing the worst case noise. Make sure that the noise levels are within specification (i.e. typically 10%)

    Make sure there is no noise on the reset line and that it is pulsed low then a solid high for the correct period once the power supplies are stable.

    If possible do an I2C read back of all the registers you write to to make sure there is no corruption and that the correct values are being written.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Prodigy 250 points

    Hi Steve,

    I am also working on this issue with Ronak here.  We have checked an confirm that noise level is withing 10% only.


    We are able to to read and write entire I2C space of THs8200 without any problem.  When we change THS8200 into Master mode by I2C register write then we can see the color bar pattern on the display as well which ensures that assembly of the THS8200 and output circuitry up to Display connector looks okay.

    Is there any possibility that any of the R,G or B lines are not toggling perfectly and hence THS8200 is not able to generate output VS signals?

    BR,

    Kartik Gandhi

  • 0 in reply to kartik gandhi
    TI__Mastermind 43875 points

    The digital RGB lines will have no effect on H/V sync outputs unless you are using embedded sync mode.

    If master mode works then it does imply that the THS is not receiving the H, V and/or FID correctly. It is also possible that some registers are not correct but this is less likely.

    Can you please check VDD_IO is at the correct level and that the digital inputs (H/V/RGB etc...) are swinging to within 5% of the upper and lower levels of VDD_IO?

    BR,

    Steve