i.MX ProcessorsのトピックRe: How can I define the lcdif_modedb ??

How can I define the lcdif_modedb ??

호영노 — Fri, 01 Dec 2017 08:16:13 GMT

Hi,

I testing the LCD output but I cannot see a perfect and clear output yet.

My First Question was this : ADV7125 with Imx6 is not working normally

I found out DISP0_DAT16~DISP0_DAT23 was not set normally.

So I can see red color now.

But I cannot calculate the correct timing for my resolution.

I wanna set the my frame buffer to 640x480, 60Hz, RGB24, bpp=32.

I set the lcdif_modedb like this :

{
"640x480", // name
   60, // refresh
   640, // xres
   480, // yres

39721, // pixclock

16, // left margin (HBP) Back Porch
48, // right margin (HFP) Front Porch

2, // upper margin (VBP) Back Porch
25, // lower margin (VFP) Front Porch

96, // Hsync Length
2, // VSync Length

FB_SYNC_CLK_LAT_FALL, // Sync
FB_VMODE_NONINTERLACED, // Vmode
0,},

Actually, I refer from below data. from googling.

But this make shifted output.

My upper setting value makes better output. Like this :

This Image is 4 seperated color that (R 255), (G 255), (B 255), (R255G255B255).

Red and green, blue and white's boarder line looks like gradation.

My original image is this : (640 x 480)

At this time, fbset's result is

mode "640x480-62"
# D: 25.176 MHz, H: 31.469 kHz, V: 61.826 Hz
   geometry 640 480 640 480 32
   timings 39721 16 48 2 25 96 2
   rgba 8/16,8/8,8/0,8/24
endmode

PCLK and VSYNC is holded.

but HSYNC looks like jitter. (little bit.. shaking..)

I cannot understand..

So I tried another timing and resolution.

I setted

{
"1280x960", // name
60, // refresh
1280, // xres
960, // yres

9794, // pixclock

216, // left margin (HBP) Back Porch
80, // right margin (HFP) Front Porch

30, // upper margin (VBP) Back Porch
1, // lower margin (VFP) Front Porch

136, // Hsync Length
3, // VSync Length

FB_SYNC_CLK_LAT_FALL, // Sync
FB_VMODE_NONINTERLACED, // Vmode
0,},

And result is

Image size is 640x480 and resolution is 1280x960

so, I understood height is half.

but I cannot understand why width is not half..

Most of all,

Left and middle's border line looks like blur and gradation..

How can I found the exact timing for 640 480 resolution?

Re: How can I define the lcdif_modedb ??

igorpadykov — Fri, 01 Dec 2017 11:02:50 GMT

Hi 호영 노

according to example in datasheet ADV7125 on p.13 : "Dot Rate = 1024 × 1024 × 60/0.8 = 78.6 MHz"
http://www.analog.com/media/en/technical-documentation/data-sheets/ADV7125.pdf

so for pixel clock one can try: 640x480x60/0.8=23.040MHz

Best regards
igor
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Re: How can I define the lcdif_modedb ??

호영노 — Fri, 01 Dec 2017 11:59:51 GMT

Thank you for reply.

I tried, but nothing changed,

{

   "LCD-720P", // name
   60, // refresh
   640, // xres
   480, // yres

43402, // pixclock

48, // left margin (HBP) Back Porch
16, // right margin (HFP) Front Porch

2, // upper margin (VBP) Back Porch
11, // lower margin (VFP) Front Porch

96, // Hsync Length
2, // VSync Length

FB_SYNC_CLK_LAT_FALL, // Sync
FB_VMODE_NONINTERLACED, // Vmode
0,},

// fbset Data :

mode "640x480-58"
   # D: 23.040 MHz, H: 28.801 kHz, V: 58.183 Hz
   geometry 640 480 640 480 32
   timings 43402 48 16 2 11 96 2
   rgba 8/16,8/8,8/0,8/24
endmode

Could you tell me how can I determine the "Retrace Factor" ?

I think that datasheet's 0.8 is just example.

So I think that we have to find exact value.

(Should I adjust another timings value? ex) front porch, back porch etc..)

Re: How can I define the lcdif_modedb ??

igorpadykov — Fri, 01 Dec 2017 23:05:37 GMT

for linux fb_mode settings one can look at sect.2.4.1 Timing Concepts AN3974
https://www.nxp.com/docs/en/application-note/AN3974.pdf
pixel clock calculations example:
https://community.nxp.com/thread/308170#comment-422519

Best regards
igor

Re: How can I define the lcdif_modedb ??

호영노 — Tue, 05 Dec 2017 00:53:41 GMT

This problem is not caused by timing..

It was solved by remove the RGB capacitor.. lol.....

Thank you for your concern of my problem.