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6-bit color output

Dean Wedel
Intellectual 760 points

I am using the Starterware LCD code on a Beaglebone-Black for driving "24-bit" raster output and it works very well. However, I am changing my LCD hardware to a HannStar model HSD070PWW1-B which is "18-bit" color (i.e. 6-bit per RGB pixel).

Can someone tell me what register settings need to be changed in the Starterware code in order to properly drive "18-bit" rather than the currently configured "24-bit"? I'm guessing something inside the Starterware function "RasterModeConfig()" but I'm needing help. . .

Thanks in advance!

Dean

  • 0
    TI__Intellectual 870 points

    Hi Dean,

    The AM335x LCD controller will not support direct configuration of 18 BPP mode.  This controller supports only 1, 2, 4, 8, 12, 16, 24 BPP Modes.

    To support 18 bit mode, the controller still needs to be configured in 24BPP mode only and based on the hardware connections, six bits in each of the pixel(2 bits each for R,G,B) will become don't care values. That is frame buffer will contain 24 BPP data, out of which 6 bits in each pixel are don't care bits.

    Please refer the following section "13.3.5.2 Frame Buffer" in AM335x TRM to get more information on frame buffers.

    Regards,

    M.Jyothi Kiran

     

     

  • 0 in reply to Madana Jyothi Kiran
    Intellectual 760 points

    Madana:

    Thanks for your reply. Through experimentation I had arrived at the conclusion that I need to use the "24-bit" mode and that the lower 2-bits where discarded by the hardware level. The coloring started out looking pretty "unusual" to start out with.

    So for now I'm simple RIGHT-SHIFTING each of the 3 color channels (red, green, blue). However, I wish there was a way to do a "compression" rather than simply truncating those color-bits. I get banding in areas where there is suppose to be color-gradient-blending. Any suggestions for that?

    Sincerely,

    Dean

  • 0 in reply to Dean Wedel
    TI__Intellectual 870 points
    Hi Dean,
    No compression techniques are supported in AM335x LCD controller. Only way to support 18 bit output is discarding 6 bits in each pixel.
    Regards,M.Jyothi Kiran