Program Your Own FPGA Video Game -- Episode 353

Hi!

I'm new to FPGAs, Digital systems and Verilog.

I have a question.

Does the game use any type of register? If that is the case, how does it use it?

Thank you very much!

This certainly didn't seem like your first Verilog. I'm even more impressed. Even if (worst case) the screen is shifted over by a pixel I'm not sure it would matter. The horizontal porch should prevent any weird wraparound effects.

I'm currently looking at my own VGA game - inspired by your post and some others I've found online that take a different approach for some of it. I like the way you've broken out the components. Once I feel I know a little more I might feel I'm in a better position to contribute.

Thanks for your question! Yes, you're probably right about the delay. Please note that this was the first Verilog code I ever wrote, right after blinking an LED, so I'd be surprised if there weren't a few bugs. Fortunately it was "good enough" to produce a stable display.

The code is under the MIT License so you're welcome to modify and share it freely. Some day if I have the time I'll go back over it with a fine-tooth comb.

Firstly, thanks for a great project which was well explained. I know this is a few months old have a question and I'm hoping somebody might have a gem of wisdom. Vga.v and Renderer.v are both clocked. The screen position is output from Vga and fed to rendered. The pixel colour is output from Renderer and fed to Vga. The relevant bit of the code are summarized below. I know Verilog isn't the same as sequential code, but wouldn't this give a one clock cycle delay calculating the colour for the position?

module Vga(
     input pixelClock,
     input [2:0] activePixel,
     output reg [15:0] screenX,
     output reg [15:0] screenY
);

always @(posedge pixelClock)
begin
     screenX <= [calculated];
     screenY <= [calculated];
end
endmodule

module Renderer(
     input pixelClock,
     input [15:0] screenX,
     input [15:0] screenY,
     output reg [2:0] screenPixel
);

always @(posedge pixelClock)
begin
  screenPixel <= [calculated from various inputs including screenX and screenY]
end
endmodule

HELLO,

I am trying to do the same thing but with the DE10-NANO board, I tried to change the corresponding PINS but still no sound when I press the KEY 0 and KEY1.

all your advices are welcome

Thanks in advance

Hey, gsharpe! It's always great to hear from people trying the project themselves. Thanks for sharing your experience using an unofficial NES controller. I also used a "replacement" controller. I wonder if anyone has tried an original, 30-year-old gamepad? Anyway, glad to hear you enjoyed the video and thanks again for sharing these workarounds with the community!

Great video!  I learned quite a bit while recreating the project on my board and, as luck would have it, ran into a problem when trying to make use of a cheap knockoff version of the NES controller.  I found that when pressing the right arrow button, it would register both the right arrow (last bit of the shift register) AND the 'a' button (first bit of the shift register).  With the original project timing for the controller, I tried to investigate the knockoff's strange behavior.  When pressing the 'a' button, it appeared to asynchronously latch properly as would be done with the CD4021 shift register of the original controller, but if the right arrow was pressed, the output remained low through the next latch pulse and the output would not change until the first clock pulse rising edge when the 'b' button value shifted out.  I still don't know why it behaves this way, but I found two methods for a workaround.  The first and simplest is by setting the 'CONTROLLER_PULSE <= 1;' in the idle state of the NesController.v file's state machine, so that the clock signal is normally high.  The other way that worked was to add another state which added an extra clock pulse.  Either way just meant there were eight rising edges instead of seven for each readout and this works for both the original and knockoff versions.  I hope this helps anyone who encounters this issue!

That's great! Enjoy your new FPGA board and let us know what cool things you create.

Thanks for the information. I'm up and running

Very well done!  This was a great project and your results are great.  You did a very good job walking the viewers through the steps, introducing concepts and demonstrating the results.

Thanks!

Gene