stm32f429 Disco direct to VGA Monitor

Forum|Forum|12 years ago
October 9, 2013
7 replies
2761 views

Posted on October 09, 2013 at 15:35

Hello :)

I just remove the LCD from one of my board and made a R2R Resistor DAC connected to the LCD dedicated pin.

The only pins you need are the 3 x 6bits colors , the vsync , hsync and GND.

After some changes in one of the examples source from ST i was able to get a picture

to my VGA Monitor ;)

I just don't have the correct timing for view 640 x 480 picture , the monitor report me a 800 x 600 resolution with 31.4Khz Horizontal and 52.3Hz refresh time ... Hmmm

I probably don't understand correctly the data-sheet/app note about the timing.

Or i put wrong parameter for sync time + bach porch etc ...

For those who want try i attach the source to put in the

\Projects\Peripheral_Examples\ directory and the R2R Schematic i do for this test.

If someone get the correct timing setup for 640 x 480 resolution i will be happy to get it ;)

It's allot more comfortable to play with a big monitor , just no touch screen here , next step is to use a USB KB + Mouse ... he he he

Cheers.

PS : i compiled this with Keil..

#stm32f429-disco-vga-monitor #32f429-disco-vga-monitor-image #vga-disco-take-it #instead-of-desoldering-the-lcd

[ATT]4095.pdf

[ATT]4094.zip

This topic has been closed for replies.

warcatzAuthor

Associate III

Posted on October 09, 2013 at 17:04

Little update.

I corrected some of my mistake , now i get picture perfect fitted into the screen.

made change in :

void LCD_Init(void)
{ 
.....
/* Timing configuration */ 
/* Configure horizontal synchronization width */ 
LTDC_InitStruct.LTDC_HorizontalSync = 96;//96
/* Configure vertical synchronization height */
LTDC_InitStruct.LTDC_VerticalSync = 2;//2
/* Configure accumulated horizontal back porch */
LTDC_InitStruct.LTDC_AccumulatedHBP = 144; //HSync + HBP = 144
/* Configure accumulated vertical back porch */
LTDC_InitStruct.LTDC_AccumulatedVBP = 35; //VSync + VBP = 35
/* Configure accumulated active width */ 
LTDC_InitStruct.LTDC_AccumulatedActiveW = 784;//144 + 640 = 784
/* Configure accumulated active height */
LTDC_InitStruct.LTDC_AccumulatedActiveH = 515;//35 + 480 = 515
/* Configure total width */
LTDC_InitStruct.LTDC_TotalWidth = 800; 
/* Configure total height */
LTDC_InitStruct.LTDC_TotalHeigh = 525;
LTDC_Init(<DC_InitStruct);
}

Now i have to found why i don't get uniform colors , in the picture attached you will see

that the 'Green' background is changing

Anyway , it's a good start :)

Cheers.

________________

Attachments :

32f429_capture.jpg : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzhX&d=%2Fa%2F0X0000000bPU%2F5EeQ5o6RvWDq3k2cLTpipeWLHD0A_TTT5m75NtnjMmc&asPdf=false

warcatzAuthor

Associate III

Posted on October 09, 2013 at 21:24

I finally found why the colors was not uniform.

we use 18bits / pixels but when we do the SDRAM test , every bits are write and for some reason when we write to Video memory after this we have a 'mix' ;) The easy way to prevent it is to erase the part of the SDRAM we use for the Video. For made simple i just erase all SDRAM after the SDRAM test , it's just a copy/paste from this code :

/* Erase SDRAM memory */
for (counter = 0x00; counter < IS42S16400J_SIZE; counter++)
{
*(__IO uint16_t*) (SDRAM_BANK_ADDR + 2*counter) = (uint16_t)0x00;
}

That's it :) Now the picture is perfect and i can look deeper in the new ST beast ;) Cheers.