720x576i in T20

onomatopeja · July 25, 2019, 9:59am

I have Colibri T20 with Iris
I would like to connect external glasses to my Iris over DVI->VGA signal
My glasses need composite signal
I made simple converter “RGB to NTSC/PAL Encoder” with AD724 https://www.analog.com/media/en/technical-documentation/data-sheets/AD724.pdf
Signal road: T20 → IRIS → VGA → AD724 → GLASSES

What have I done:

I add 720x576i to to drivers/video/tegra/dc/mode.c

.

{
     /* 720x576i @ 50 Hz , pixel clk @ 13.5MHz */
     "LCD-PAL", 50, 720, 576, 74074, 138, 24, 39, 4, 126, 6,
     0,
     FB_VMODE_INTERLACED,
     0,},

save in in uboot setenv vidargs video=tegrafb0:720x576-32@50 ; saveenv; reset
restart and check fbset

mode “720x576-50”
# D: 27.000 MHz, H: 31.250 kHz, V: 50.000 Hz
geometry 720 576 720 1152 32
timings 37037 68 12 39 5 64 5
rgba 8/0,8/8,8/16,8/24
endmode

Where is the problem ?
I need pixel clk 13.5MHz but i see in fbset 2x13.5MHz
Who knows how to set the resolution ? 720x576i

onomatopeja · July 26, 2019, 9:29am

Alternative approach to the problem: I used cmd

fbset -g 720 576 720 576 32 -t 74074 68 12 39 5 64 5 -laced true -hsync false -vsync false
and check result from fbset

mode "720x576-50"
    # D: 13.500 MHz, H: 15.625 kHz, V: 50.000 Hz
    geometry 720 576 720 1152 32
    timings 74074 68 12 39 5 64 5
    laced true
    rgba 8/0,8/8,8/16,8/24
endmode

D: 13.500 MHz, H: 15.625 kHz, V: 50.000 Hz All correct
But i test oscilloscope and have V: 25Hz

marcel.tx · July 26, 2019, 3:33pm

Unfortunately, using fbset for run-time configuration is not supported:

marcel.tx · July 26, 2019, 3:35pm

I doubt doing interlaced like that or at all is supported.