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Observer
Observer
5,145 Views
Registered: ‎11-14-2009

Help with VGA on Digilent Nexys2: Monitor displays blank

Hi,

 

Problem: Monitor displays blank state

 

      I am trying to display images on a monitor. I am using the VGA controller code provided by Digilent that uses a 25Mhz from a DCM and outputs HS and VS signals (which I tested for correct timing). The controller also provides two 11bit horizontal (vecHcount_640_60) and vertical (vecVcount_640_60) pixel address counter buses. I have instantiated this controller in a main VHDL module that communicates with the Microblaze and also provides a 6336 (88 x 72) 8bit byte array which I intend to use as Video ram. The board has termination resistors for 8-bit RGB data. Digilent's built in test code works and displays some psychedelic stuff. 

 

 

    type ram_type is array (0 to 2** 13) of std_logic_vector( 0 to 7) ;
    signal video_ram : ram_type;

 

-----  I use  the following code bit to map the 11 bit buses to the video ram.

 

    RGB_OUT_temp <= video_ram(conv_integer(conv_integer(vecHcount_640_60)+(88*conv_integer(vecVcount_640_60))))   
                            when ((vecHcount_640_60 < 88) AND (vecVcount_640_60 < 72)) else (others => '0');
   
    --RGB_OUT <= RGB_OUT_temp when bitBlank640_60 = '1' else (others => '0');
    RGB_OUT <= "10100100";
    

 

  As you can see, I even tried setting RGB_OUT to some random color and the monitor is still blank. Monitor seems to recognize HS and VS which I already verified on an oscilloscope. 

 

  Is there something fundamental I am missing here? I looked into a couple of other example codes but did not notice anything odd. 

 

 

 

Regards,

 

Karthik

 

 

 

    

Message Edited by karvi_in on 12-15-2009 01:23 AM
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Visitor
Visitor
5,136 Views
Registered: ‎11-02-2008

Re: Help with VGA on Digilent Nexys2: Monitor displays blank

try to use XPS_TFT controller which is available since EDK 10.1.03.

 

Tom

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Observer
Observer
5,105 Views
Registered: ‎11-14-2009

Re: Help with VGA on Digilent Nexys2: Monitor displays blank

It works now. Turns out the monitor I tested my code on was broken.
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