I am working on an FPGA board and coding in Verilog. I am trying to use the MicroJoystick installed on LogicStartMegaWing, the shield with Papilio-One 500k (my FPGA board). I have to do simple tasks like increment or decrement a reg variable on different movements of the joystick. Initially I was running the above code in an alwaya @ (SWITCH) block i.e. the block will be running whenever there is a movement in joystick (on this board joystick shares the pins with five switches). This led to complete loss of control of the cursor on the VGA display (very fast multiple increments or decrements), even on slightest movement of the joystick.
Then I ran the same code in an always @ (slowclk) block where 'slowclk' is a 1Hz clock. This led to improvement as there were finite, slower increments or decrements. However, the problem is not completely resolved i.e. on one move of the joystick there are multiple increments to the reg.
How can I remove this debounce from the input through the joystick? Need some help on this. I am also putting my code to generate the slowclk and to use the joystick.
THE COMPLETE REVISED CODE:
//This increments/decrements number and displays on seven segment display on
//up/down movement of joystick; in an array of 8 LEDS shifts the glowing LED to
//right or left on left/right movement of joystick
//joystick (i.e. [4:0] SWITCH here) by default gives all ones
// input clock is at 32 Mhz
module Display(
input clk,
input [4:0] SWITCH,
output reg [3:0] Seg7_AN,
output reg Seg7_A,
output reg Seg7_B,
output reg Seg7_C,
output reg Seg7_D,
output reg Seg7_E,
output reg Seg7_F,
output reg Seg7_G,
output Seg7_DP,
output reg [7:0] LED
);
reg [3:0] number;
wire [4:0] clean;
Debounce stable(.clk(clk), .SWITCH(SWITCH), .clean(clean));
initial
begin
LED = 8'b00000001;
end
assign Seg7_DP = 1;
always @ (clean)
begin
if(clean[0]==0)
begin
if (number==9)
number <= 0;
else
number <= number+1;
end
else if (clean[1]==0)
begin
if (number==0)
number <= 9;
else
number <= number -1;
end
else if (clean[3] == 0)
begin
if (LED == 8'b00000001)
LED <= 8'b10000000;
else
LED <= LED >> 1;
end
else if (clean[4]==0)
begin
if (LED == 8'b10000000)
LED <= 8'b00000001;
else
LED <= LED << 1;
end
end
always @ (*)
begin
Seg7_AN <= 4'b0111;
case (number)
0 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=0 ; Seg7_F<=0 ; Seg7_G<=1 ; end
1 : begin Seg7_A<=1; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=1 ; Seg7_E<=1 ; Seg7_F<=1 ; Seg7_G<=1 ; end
2 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=1 ; Seg7_D<=0 ; Seg7_E<=0 ; Seg7_F<=1 ; Seg7_G<=0 ; end
3 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=1 ; Seg7_F<=1 ; Seg7_G<=0 ; end
4 : begin Seg7_A<=1; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=1 ; Seg7_E<=1 ; Seg7_F<=0 ; Seg7_G<=0 ; end
5 : begin Seg7_A<=0; Seg7_B<=1 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=1 ; Seg7_F<=0 ; Seg7_G<=0 ; end
6 : begin Seg7_A<=0; Seg7_B<=1 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=0 ; Seg7_F<=0 ; Seg7_G<=0 ; end
7 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=1 ; Seg7_E<=1 ; Seg7_F<=1 ; Seg7_G<=1 ; end
8 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=0 ; Seg7_F<=0 ; Seg7_G<=0 ; end
9 : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=1 ; Seg7_F<=0 ; Seg7_G<=0 ; end
default : begin Seg7_A<=0; Seg7_B<=0 ; Seg7_C<=0 ; Seg7_D<=0 ; Seg7_E<=0 ; Seg7_F<=0 ; Seg7_G<=1 ; end
endcase
end
endmodule
module Debounce(
clk, SWITCH, clean
);
input wire clk;
input wire [4:0] SWITCH;
output reg [4:0] clean = 0;
reg [18:0] count = 0;
reg [4:0] new = 0;
SlowClock OneKHz (.clk(clk), .slowclk(slowclk));
always @(posedge slowclk)
begin
if (SWITCH != new)
begin
new <= SWITCH;
count <= 0;
end
else if (count == 20)
begin
clean <=new;
count <=0;
end
else
count <= count+1;
end
endmodule
module SlowClock(
input clk,
output reg slowclk
);
reg [63:0] i;
parameter delay = 32000;
initial
begin
slowclk = 0;
i = 64'd0;
end
always @ (posedge clk)
begin
if (i<delay)
begin
i= i+1;
end
else
begin
i = 64'd0;
slowclk = ~slowclk;
end
end
endmodule
