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Altera_Forum
Honored Contributor I
778 Views

DE1 to DE2-115, VGA module errors

Greetings everyone, I've been a reader of these forums for a few years now and am starting to get a bit more active in the community. I'm a first year graduate student who purchased a DE1 development board shortly after finishing undergrad (we used a DE2 in the curriculum). 

 

When possible, I like to write my own modules and, when I was primarily using the DE1, I wrote a VGA driver in Verilog. I used the driver in some small projects (like pong and flashing screens), and, at the time, was proud of myself and happy it worked. 

 

Now, I have my DE2-115 which brings with it many more LE and some more "modern" I/O for me to learn to use. When I went to try out my new system, however, I found out my VGA module no longer works! 

 

I've found a new pin that was not present on the DE1: VGA_CLK. I'm really at a loss as to why nothing works. I've gone back to basics and tried just getting the screen to turn red via the switches with no other components but it still does not work.  

 

My module expects a 50MHz clock into that goes into a PLL (internally) in order to create the ~25MHz clock for the module. Looking at Altera's demo for their TV project, I see they use the TD_CLK27 for the input to their module and just forward ~TD_CLK27 to VGA_CLK.  

 

Anyway, does anyone know what I need to do to port my DE1 VGA module to the DE2-115? If anyone wants to see code I can post some or all of it but didn't want to flood the board right away. Thanks everyone.
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Altera_Forum
Honored Contributor I
62 Views

 

--- Quote Start ---  

Now, I have my DE2-115 which brings with it many more LE and some more "modern" I/O for me to learn to use. When I went to try out my new system, however, I found out my VGA module no longer works! 

 

I've found a new pin that was not present on the DE1: VGA_CLK. 

--- Quote End ---  

 

 

The DE1 has a simple VGA interface. The DAC, that convert the color output from digital to analog, is just a resistor ladder. 

 

DE2 boards don't use a resistor ladder anymore. They include instead a dedicated DAC chip manufactured by AD. This chip requires the new VGA_CLK signal. 

 

There a few extra signals involved that you need to take care, such as VGA_BLANK, VGA_SYNC, and the color bit depth was also increased. Check the DAC datasheet and the schematics.
Altera_Forum
Honored Contributor I
62 Views

Thanks for the response! I did take care of the VGA_BLANK_N and VGA_SYNC_N signals already and went back to my DE1 and started from scratch. So far the projects works on the DE1. So, I'm going to start a more formal port instead of just throwing code in expecting it to work.  

 

Previously, I did take a look at the data sheet for the VGA chip but brushed it off not thinking it would make my module not functional. This was a mistake on my part and I should have know hardware isn't as forgiving as I'd like it to be sometimes. 

 

I'll take a deeper look at the difference between the boards and figure out any new signal propagation I may need to implement. Thanks for the advice!
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