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DSS data lines not working

Andrew Poole
Intellectual 570 points
Other Parts Discussed in Thread: OMAP3530

Hi,

I have a problem whereby I am not seeing activity on all DSS data pins. I am seeing activity on DSS_DATA[21..16] and DSS_DATA[9..6] but the other 18 lines remain stuck low. I have noticed from the data sheet that the non-working pins appear to be in a different area of the chip than the working ones. All the non-working pins are in the area AA22 to AH24 whereas the working pins are in the area E26 to J26.

Is there any specific set up required to enable power to a specific area? or indeed a reason why some of the pins should work and some don't? I should add that due to I2C problems on the hardware, I have had to remove the enabling of the power regulator in 'drivers/video/omap2/dss.dpi.c':

 

int omapdss_dpi_display_enable(struct omap_dss_device *dssdev)
{
    ...

    // if (cpu_is_omap34xx()) {
    //      r = regulator_enable(dpi.vdds_dsi_reg);
    //      if (r)
    //           goto err1;
    // }

    ...
} 

Could this be having any affect on why I am not seeing many of the DSS_DATAn pins functioning correctly?

Thanks,

 

 

Andy

  • 0
    Intellectual 570 points

    Further to my last post, I have discovered that the failing DSS_DATA lines are multiplexed to balls with an IO CELL type of LVDS/CMOS. I can confirm that, from reading the DSI_VCn_CTRL registers, the mode speed is correctly set to CMOS.

    I cannot find any useful documentation on this set up. Is the Power Chip required for a ball with an IO CELL type of CMOS (instead of LVCMOS).

    Any help would be appreciated.

     

    Andy

  • 0 in reply to Andrew Poole
    Prodigy 30 points

    Hi,

    I have the same problem. We use the OMAP3530-EVM board as a reference design.

    I draw a full blue rectangle R=0x00,G=0x00 and B=0xFF.  and the bit DSS_D0   =0 whereas it should be equal to 1. We think about config problem but we don't find the solution.

    Our problem is critical as we work with an FPGA and use this bit to enable Alpha we other video from FPGA.

    any help would be appreciated.

    Regards,

  • 0 in reply to thibaut desbrugeres
    Prodigy 30 points

    Hello Again,

    we have found the soulution for our problem (maybe it's the same for you).

    This is a parameter in the bootargs command line :

    omapfb.video_mode="800x600MR-24@50"

    whereas before, we had :

    omapfb.video_mode="800x600MR-16@50"

    regards,


  • 0 in reply to thibaut desbrugeres
    Intellectual 570 points

    Hi,

    Glad you sorted out your problem, sadly my problem was not a case of configuring the DSS to read 24bit pixels instead of 16 (as in your case).

    After much digging around on Google, I have found a/the reason why certain data lines were not being enabled. When looking at the Pad Configuration registers (CONTROL_PADCONF_DSS_DATAn), some of the parallel LCD outputs are shared with DSI and SDI pads, which seem to require the power from a IC Power chip. Even though I am not using the SDI or DSI protocols, the IC Chip still appears to be needed to power the pads. Hopefully TI can confirm this?

    Regards,

     

    Andy

  • 0 in reply to Andrew Poole
    TI__Genius 16690 points

    Hello Andy,

    Could you tell me Which device and package you are using ?

  • 0 in reply to kshin
    Intellectual 570 points

    Hi Kazunobu,

    I am using an OMAP3530, CBB package.

     

    Andy

  • 0 in reply to Andrew Poole
    TI__Mastermind 43875 points

    Andy,

    Can you please let me know what value you have in hardware register 0x48050440 ?

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Intellectual 570 points

    Hi Steve,

    The hardware register DISPC_CONTROL 0x48050440 has a value of 0x00018309:

    • LCDENABLE = 0x01
    • STNTFT = 0x01
    • TFTDATALINES = 0x03
    • GPOUT0 = 0x01
    • GPOUT1 = 0x01

    Is there a register setting that will give power to all DSS_DATA pads without the need for the IC power chip then?

     

    Andy

  • 0 in reply to Andrew Poole
    TI__Mastermind 43875 points

    Ady,

    Thanks.

    I just wanted to do a sanity check on the DSS configuration.

    I don't know about the power side of things unfortunately.

    BR,

    Steve

  • 0 in reply to Andrew Poole
    TI__Genius 16690 points

    Hello,

    All VDDS (IO power plane) power supply signals listed in Table 2-25. Power Supplies Signals Description in the OMAP3530 data manual have to be powered by the same power source. Please confirm below signals are connected to the same power supply.

    AD3 / AD4 / W4 / AF8 / AE8 / AF16 / AE16 / AF23 / AE23 / F25 / F26 / AG27/ AE27/ AG20/ H28/ AG21

  • 0 in reply to kshin
    Intellectual 570 points

    Hi Kazunobu,

    I am not completely familiar with the hardware but I believe that that the TI OMAP3530 EVM has been used as a model and our layout is based on that. Looking as the schematic, the signals you mention are not all connected to the same supply; AE27 and AG20 are supplied by the IC Power chip - the same as the TI EVM (and in fact the Beagleboard). Is this incorrect?

  • 0 in reply to Andrew Poole
    TI__Genius 16690 points

    Hi Andrew,

    AG21 and AE27 need to be powered up with 1.8 V power supply to use all DSS data lines. Please turn on the power supply connected to these pads if it's off.

  • 0 in reply to kshin
    Prodigy 30 points

    Hi,

    may be  it's the same problem.

    I have the same problem with D_8 (Green bit 0). When I drawn a rectangle with 0x01 in this bit, there is some time a mismatch.

    at the middle of a line (acbias says this line is valid) the bit goes down during  about 27 pixels in 800x600@ 50Hz configuration,

    and I don't know why.

    when we receive the OMAP3530 evm board, the board was in 16 bits 600x480.

    Could you tell me if we can use the DSS in 24 bits with OMAP-EVM board. The AG21 and AE27 is powered by VDD_PLL2 (PMIC) ?

    If yes how we can do ?

     

    Regards

  • 0 in reply to thibaut desbrugeres
    TI__Genius 16690 points

    The 24 bits DSS data is used for the DVI interface however only 18 bits data are connected to the LCD panel interface in the OMAP3EVM.