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: 1646

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

Profile IconRichard Vincent, KrisWiner and tools4u joined GarageLab (arduino, electronics, robotics, hacking)
2 hours ago
GarageLab posted blog posts
Wednesday
Profile IconJ.J.J. Kuipers and Phan Minh Kha joined GarageLab (arduino, electronics, robotics, hacking)
Wednesday
GarageLab posted a blog post

Electric lawn mower converted to RC control

Not too many people like pushing a lawn mower around the yard, but unfortunately, it is a necessary…See More
Monday
Profile Iconchiran sachintha and Blun Blun joined GarageLab (arduino, electronics, robotics, hacking)
Monday
GarageLab posted a blog post

Codename Colossus: The HMC Boudicca

[Michael Sng], founder of [Machination Studio], wanted to create a toy line unlike anything the…See More
Jun 26
Fernando Rodrigues Pontes is now a member of GarageLab (arduino, electronics, robotics, hacking)
Jun 26
GarageLab posted blog posts
Jun 23
Profile IconSayed Akbar Rajaei Ramsheh, william sarte and Ahmed OUKERROUM joined GarageLab (arduino, electronics, robotics, hacking)
Jun 23
GarageLab posted a blog post

Dashboard in you simulator!

 Fans of driving simulator games not only play with steering wheels, gear shifters and pedals. Some…See More
Jun 22
Jesus M Andino commented on GarageLab's blog post Diabetes Has a New Enemy: Robo-Pancreas
"How will be the sugar regulated when there is a higher demand of it due to stress situations? "
Jun 19
GarageLab posted blog posts
Jun 19
GarageLab posted blog posts
Jun 17
AnalysIR posted a blog post

Porting AnalysIR firmware to Particle’s Photon platform

We have just finished porting our (single source) firmware from a range of other ‘Arduino’ type…See More
Jun 17
Profile Iconabin joseph, ATony and cocowei joined GarageLab (arduino, electronics, robotics, hacking)
Jun 17
Michael updated their profile
Jun 15
lovakiranvarma replied to Kringen's discussion MSP430 Launch Pad
"hi! Kringen even though Energia is promissing! But in my opinion it won't much helpful…"
Jun 14
GarageLab posted a blog post
Jun 12
AnalysIR posted a blog post

Simple Infrared PWM on Arduino, Part 2- RAW IR Signals

In Part 1 of this series, we demonstrated how to send signals using simple Infrared PWM on Arduino.…See More
Jun 12
Profile IconJesus M Andino, Aaron Armstrong and edmund joined GarageLab (arduino, electronics, robotics, hacking)
Jun 12

© 2015   Created by Marcelo Rodrigues.

Badges  |  Report an Issue  |  Terms of Service