Hello everyone, 

Going forward on my study about VGA signal, now I could generate the sync signals (horizontal and vertical), and also play with the RGB ones. Now I can generate vertical color bars and rectangles. :)

I am still facing some problems, like to fill the entire screen area (it still shows an empty bar on the right), but I think I can solve this with a better adjust on horizontal timing.

Besides, not all kind of monitors can recognize my signal, some LCDs are not ok (no problem for CRT). I believe the solution is a better adjust on timing and/or impedance coupling.

Take a look what I got so far:

This was the first step: generate a solid stable rectangle on screen. It is white because I put all the RGB bits to HIGH, but the important was the sync signals worked very well (I think). 

The ugly/terrible picture above (the camera and my photographic skills didn't help), shows the colored vertical bars I could get from my Arduino UNO, changing the RGB bits. Actually, it would be possible to generate many more colors using some tricks or simply changing the analog levels of the RGB bits (0 to 0.7V), but I think Arduino wouldn't have speed enough on DAC. Well, for me, there is A LOT to learn yet.  

Below you can check the code, which I am not very proud of, but i works!!! :)). I think it can be useful for somebody: 

#define NOP asm("nop")
#define BLACK PORTB = B00000000;
#define BLUE PORTB = B00000001;
#define GREEN PORTB = B00000010;
#define CYAN PORTB = B00000011;
#define RED PORTB = B00000100;
#define MAGENTA PORTB = B00000101;
#define YELLOW PORTB = B00000110;
#define WHITE PORTB = B00000111;

unsigned int linecount = 1;

void setup()
{
//Set pins 5, 6 e 7 as output
// 7 - HSYNC
// 6 - VSYNC
// 10 - R
// 9 - G
// 8 - B

DDRD |= B11100000;

DDRB |= B11100111;
PORTD |= B11000000;

//set timer
TCCR2A = 0x02; // WGM22=0 + WGM21=1 + WGM20=0 = Mode2 (CTC)
TCCR2B |= (1 CS20); //
TCCR2B |= (1 CS21); // Set prescaler
TCCR2B &= ~(1 CS22); //

TCNT2 = 0; // clear counter
OCR2A = 0x0f; // set counter for comparison

TIMSK2 |= (1OCIE2A); // set interrupt by comparison
}

 

void loop()
{
do{
}while(1);

}

 

ISR(TIMER2_COMPA_vect){
PORTD &= ~(1 7);
if (++linecount == 525){ //525 lines
linecount = 1;
}
PORTD |= (1 7);

NOP;NOP;NOP;NOP;NOP;NOP;
if (linecount == 492){
PORTD &= ~(1 6);
} else {
PORTD |= (1 6);


if ((linecount >= 2) && (linecount <= 480)){

//Print a vertical rainbow on screen 
for (int j=0; j<6; j++){
BLACK;NOP;
BLUE;
BLACK;NOP;
GREEN;
BLACK;NOP;
CYAN;
BLACK;NOP;
RED;
BLACK;NOP;
MAGENTA;
BLACK;NOP;
YELLOW;
BLACK;NOP;
WHITE;
BLACK;NOP;
}
}

}

NOP; //small time adjust, it may or may not be necessary depending on your board

}

 

That's it! This was the first step for understand the basics about VGA, specially the SYNC signals. Now it's time for a better understanding about sizes and times. Also, the impedance coupling must be adjusted between the Arduino and the monitor (it could be the reason for some LCDs not understand my signal).

And more precision on timing is still possible.

Then, I will try to create some time windows for data acquiring, allowing the Arduino to get info to plot.

If, everything goes fine, maybe we can create a library for everyone use with any Arduino and any monitor, including TFTs. Too much maybe?? :)) 

Let's see what we gonna get! 

I will post every step, maybe they can help our friends here in GarageLab...

Thanks for reading this post! :)

Views: 2267

Comment by Ryadh on April 2, 2012 at 4:10pm

Great hope that will work on my board i will try it tomorrow thanks a lot !!

Comment

You need to be a member of GarageLab (arduino, electronics, robotics, hacking) to add comments!

Join GarageLab (arduino, electronics, robotics, hacking)

Latest Activity

Profile Iconks kr, mashkoor and Mert joined GarageLab (arduino, electronics, robotics, hacking)
yesterday
Profile IconSastri Yanamandra and Omar Stanley joined GarageLab (arduino, electronics, robotics, hacking)
Aug 17
Roosevelt Sebial is now a member of GarageLab (arduino, electronics, robotics, hacking)
Aug 16
Profile IconKristoffer Thorpe and ANKUSH ARJUN DHEKWAR joined GarageLab (arduino, electronics, robotics, hacking)
Aug 12
Marcelo Rodrigues commented on Dmitry Slepov's blog post Tibbo Project System (TPS) from Tibbo Technology
"Cool!"
Aug 11
Dmitry Slepov posted a blog post

Tibbo Project System (TPS) from Tibbo Technology

Tibbo Project System (TPS) is a highly configurable, affordable, and innovative automation…See More
Aug 11
Ghenam houssam joined Jordan Weller's group
Thumbnail

Technology Concepts & Ideas

New devices and methods of constructing things, Old and recent inventions. Scientific theory.…See More
Aug 11
Dmitry Slepov is now a member of GarageLab (arduino, electronics, robotics, hacking)
Aug 10
Profile Iconxiao1236, Tilda Anne Mclauren, Brian Edward Bailey and 1 more joined GarageLab (arduino, electronics, robotics, hacking)
Aug 9
GURUR FURKAN SARILMAZ is now a member of GarageLab (arduino, electronics, robotics, hacking)
Aug 5
Lev Artishchev is now a member of GarageLab (arduino, electronics, robotics, hacking)
Aug 2
Marcelo Rodrigues posted a blog post
Aug 2
Norman Raspin updated their profile
Aug 1
Profile Iconvirgan yusuf, Norman Raspin and Mitja joined GarageLab (arduino, electronics, robotics, hacking)
Aug 1
M.Hess updated their profile
Jul 28
Profile IconVignesh Ravindran, xgwwei, James B McCabe and 6 more joined GarageLab (arduino, electronics, robotics, hacking)
Jul 27
vivid posted a blog post
Jul 26
liuyi is now a member of GarageLab (arduino, electronics, robotics, hacking)
Jul 20
yanfan li posted a discussion

Last Chance to Grab the New Robot Starter Kit --- Fireduino

Only a week left to grab the New Smart Robot Kit --- Fireduino. Only available on Kickstarter for…See More
Jul 19
Profile Iconvivid, lihua, JorgeLuisMolinaPrudot and 2 more joined GarageLab (arduino, electronics, robotics, hacking)
Jul 19

© 2016   Created by Marcelo Rodrigues.   Powered by

Badges  |  Report an Issue  |  Terms of Service