VGA on ATmega128
      

         
Although I've done VGA signals from micro controllers many times before, I've been pondering lately on introducing a 74LS165 PISO shift register into the circuit. This would increase the resolution from the controller based on the memory available. I'm aiming for 40x25, but I wouldn't be surprised if it were capable of more.
         
I didn't finish it last night, but I'll show you the progress so far. Here's the breadboard with the shift register attached, and a crystal to it. I also decided to do all, if not most of it, in pure C.
         

         
Here's a quick VGA adapter board I made. Who said vero boards are passe?
         

         
Here's the graphics being produced by the ATmega. Not much to show, really, but I was able to verify that the timing was spot-on and the voltage levels were acceptable.
         

         
It's at a very experimental stage right now, I'm only setting the background color, playing with a few on/off's horizontally. The image is perfectly stable, no flickering or shivering.
         

         
Here's proof the signal is fine. For some reason I expected 60Hz but ended up with 59... not quite sure why, but we'll see if it's worth digging into. As of now, I don't really care.
         

         
All right, that's as far as I got last night. Next time I'll have some text on the screen! Oh, and the schematics and sources will obviously be released when I'm done.
         
Edit: Success. See here.
         
      

         
Tagged: atmega
         
      

   
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…A on the ATmega, and fought some timing issues. This is a followup on the test I did earlier ("VGA on ATmega128"), but today, I got a small breakthrough and a proof-of-concept up and running:It's based on a…
               
VGA text driver - jmp.no/blog
               
            
      
2 Comments
      

            

               
hei.. it's cool...
how about the update of this experiment? can u share the link of new progress ?..
               
            
#317 | Comment by delius on Jul 26, 2012 04:41am
               

               
            
         

            

               
Hi! Sure, see here: http://jmp.no/blog/vga-text-driver, although this is a version without the 74HC165. It's based on a 16MHz ATmega128 alone.
               
The version I'm currently working on supports text and bitmap graphics.
               
            
#318 | Comment by admin on Jul 26, 2012 07:11am
            
         
   


http://jmp.no/blog/vga-on-atmega128







   
vgavr
   

      
About
VGAVR is a simple program for generating text on a VGA monitor using a 16MHz ATmega MCU.
      
The source is written in 100% C and was developed on an ATmega128 using AVR Studio 4. It is believed to run just fine on other ATmegas at the same speed.
      
It has been tested on two monitors, and should comply to the 640x480@60Hz industry standard. However, do note that it is currently at a beta stage, so some tweaking may be required.
      
License
VGAVR is released under the GNU General Public License, see this page for details.
      
Download
The source can be downloaded here: vgavr-0.3b.zip (dated 2012-08-27)
      
Hook it up
R, G and B has a voltage level of max 0.7v, so the graphics output pin (MOSI, PB2 on ATmega128) must be via a divider to obtain the correct voltage level. VSYNC and HSYNC are TTL levels and does not require a divider.
      

      
Screenshots

      

      
   
http://www.jmp.no/blog/vgavr/