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: 1512

Tags: arduino, generator, signal, vga

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

james gage replied to Devin Moss's discussion Free-spinning high torque DC motor
"My suggestion is to investigate electromagnetic clutches. You can engage any motor with a logic…"
1 hour ago
GarageLab posted blog posts
yesterday
Rey Canedo is now a member of GarageLab (arduino, electronics, robotics, hacking)
Monday
Devin Moss posted a discussion

Free-spinning high torque DC motor

I'm looking for a high-torque DC motor (able to lift 20 pounds) which, when turned off, will spin…See More
Saturday
Marcelo Rodrigues posted a blog post
Saturday
Profile IconJack Gromek, pratik and KEKELI LOGAH joined GarageLab (arduino, electronics, robotics, hacking)
Friday
GarageLab posted a blog post

Stanford’s cheap nanomaterial filter could solve the air pollution problem

The rapidly increasing industrialization in many parts of the world comes with economic benefits,…See More
Friday
GarageLab posted a blog post

Blub Uno Clock Displays Time with One Nixie Tube

We’ve seen our share of Nixie tube clocks, but the Blub Uno is different. This is a clock that…See More
Feb 26
GarageLab's blog post was featured

LEGO X Converts Creations into 3D Models in Real Time: Body and Soul

Created by Gravity Research Club, LEGO X creates a 3D model of whatever you’re building while…See More
Feb 25
sathiyakumar is now a member of GarageLab (arduino, electronics, robotics, hacking)
Feb 24
GarageLab posted blog posts
Feb 24
Profile Iconaymen hleli, gunawan eko, Dean Sanders and 1 more joined GarageLab (arduino, electronics, robotics, hacking)
Feb 23
GarageLab posted a blog post

Street Fighter Played with Pianos: Sound Fighter

Back in 2014 we saw an piano that was turned into…See More
Feb 23
GarageLab posted blog posts
Feb 20
Profile IconRobert Choi and Pierre Gelinas joined GarageLab (arduino, electronics, robotics, hacking)
Feb 20
David Wachter commented on GarageLab's blog post DARPA is developing a sensing bionic hand
"This would be nice for all of the military amputees that have been 'produced' since the…"
Feb 18
GarageLab's blog post was featured

AirBoard: The Flying Segway

Currently up for funding on…See More
Feb 18
GarageLab posted a blog post

DARPA is developing a sensing bionic hand

Not content just to chip in creating better mind-controlled bionic limbs, DARPA is focusing on…See More
Feb 18
Profile IconAmr Anwar and recca joined GarageLab (arduino, electronics, robotics, hacking)
Feb 18
GarageLab posted a blog post

Voltera V1 Circuit Board Printer: Print-A-Sketch

The latest in the growing niche of circuit board printers, the Voltera V1 can print up to two…See More
Feb 16

© 2015   Created by Marcelo Rodrigues.

Badges  |  Report an Issue  |  Terms of Service