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: 1543

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

GarageLab posted blog posts
7 hours ago
Profile IconOleg and Scott Runner joined GarageLab (arduino, electronics, robotics, hacking)
yesterday
GarageLab left a comment for RMullen
"Hi RMullen! I'd like to let you know that FRANK KWABENA is no longer a member of…"
Wednesday
daniel gabriel updated their profile
Wednesday
daniel gabriel left a comment for daniel gabriel
"Good Day Mr. Wabena, i dont see any interesting on my profile but i really appreciated that you…"
Wednesday
RMullen replied to Lauren Elizabeth's discussion Scammed...?
"Yes there is another one sending out the same message now.  This is the message I got: FRANK…"
Wednesday
Rick Lin is now a member of GarageLab (arduino, electronics, robotics, hacking)
Wednesday
GarageLab posted a blog post
Tuesday
Profile IconCalvin M and harsha joined GarageLab (arduino, electronics, robotics, hacking)
Tuesday
GarageLab posted a blog post

These Colorful Liquid Droplets Chase Each Other Like Living Organisms

Scientists at Stanford University were at first perplexed by the strange behavior they observed…See More
Monday
GarageLab posted blog posts
Mar 20
Profile IconJody Bowie, Kevin Kvarda, Tony Stoklosa and 2 more joined GarageLab (arduino, electronics, robotics, hacking)
Mar 19
Sergey commented on GarageLab's blog post Tutorial: How to use the Monster Moto Shield
"Good day. Can you help me? I took this sketch, but it doesn't working( "
Mar 19
Profile IconDonald Soji Adedokun, Ankur Deo and Hannu Miettinen joined GarageLab (arduino, electronics, robotics, hacking)
Mar 18
GarageLab posted a blog post
Mar 18
GarageLab posted a blog post

Iron Man Delivers Kid’s Robotic Arm: Proof that Tony Stark Has a Heart

Alex Pring now has one heck of a story to tell his friends. Not only did the 7-year old meet Iron…See More
Mar 16
Profile IconJohn Murphy and Asma Ho joined GarageLab (arduino, electronics, robotics, hacking)
Mar 16
Electronicsrus is now a member of GarageLab (arduino, electronics, robotics, hacking)
Mar 13
AnalysIR commented on GarageLab's blog post Tutorial: Arduino IR sender and receiver
"@kkukkuk this problem has been discussed receltly on the Arduino forum - why not search there. You…"
Mar 13
kkukkuk commented on GarageLab's blog post Tutorial: Arduino IR sender and receiver
"hi..there are some errors in both irsend and irreceive coding.. ir sender: sketch_mar14a.ino:17:1:…"
Mar 13

© 2015   Created by Marcelo Rodrigues.

Badges  |  Report an Issue  |  Terms of Service