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Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

simple question

Hi there,

I'm trying to increment a row of leds by one but pressing a pushbutton that is normally high until it is pressed. I have this code, but for some reason, the led's just light randomly. I'm using a DE2-70 board, 18 LEDs, 1 pushbutton to reset, and 1 to increment.

module button_led(iKEY, oLEDR, iCLK_28);

output [17:0]oLEDR;

input [0:3]iKEY;

input iCLK_28;

reg [17:0]j;

assign oLEDR = j;

always @(posedge iCLK_28)

begin

if(!iKEY[0])

j <= 0;

else if (!iKEY[1])

j <= j + 1;

end

endmodule

Thanks!!

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Your code is exactly doing what you have written: increment the counter while the key is pressed. You apparently intended to increment it by one for each falling edge of the key signal.

    The key inputs are said to have debouncing circuits in the DE2-70 manual. If this is correct, the below code (synchronous edge detection) should work. 

    reg k1;
reg k2;
always @(posedge iCLK_28)
begin
k1 <= KEY;
k2 <= k1;
if(!iKEY)
j <= 0;
else if (!k1 && k2)
j <= j + 1;
end
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Thanks for the reply!

    I'll try your code tomorrow when i get the chance. I realize that i was incrementing awkwardly like that, but i also tried:

    always @ (negedge iKEY[1])

    j <= j+1;

    but that didn't give any sort of response..
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    I'm sorry, i forgot to import the assignments -_-. it works perfectly thanks!