Creating a 3 second latch for BASYS3 Button

[rb251415]

I have created a soundbox with different sounds connect to different buttons and switches. The switches work fine. High '1' is on, and low '0' is off. 

I would like my buttons to latch for 3 seconds. I would like to press the button, release it, and have the sound play for 3 seconds. Some call this a one-shot, where a single press latches the bit until unlatched.

My code is VHDL in Vivado 2016.4. My board is a BASYS3.

 

I tried using a wait statement, but others have suggested that wait statements do not synthesize. Here is what I have. All help is appreciated. Thanks!

 

period - constance set to 1000ms

tempdata - signal std_logic

squareout - signal for tone 1

integerout - signal for tone 2

ipcoreout - signal for tone 3

dataout - output from system

section of code....

D1: process
    begin  
    if btn_a = '1' then
     tempdata <= squareout;
     wait for 3 * period;
    elsif btn_b = '1' then
     tempdata <= integerout;
     wait for 3 * period;
    elsif btn_c = '1' then
     tempdata <= ipcoreout;
     wait for 3 * period;
    elsif swt_a = '1' then
     tempdata <= squareout;
     wait until swt_a = '0';
    elsif swt_b = '1' then
     tempdata <= integerout;
     wait until swt_b = '0';
    elsif swt_c = '1' then
     tempdata <= ipcoreout;
     wait until swt_c = '0';
    end if;
end process;

dataout <= tempdata; 

 

 

[D@n]

@rb251415,

Yeah, wait statements don't synthesize.

Try using a counter instead.   You can initialize it to zero (or your max value) when you come into a wait state, increment (or decrement) it while you are waiting, and then leaving when the counter reaches your maximum (or zero) value.

Dan

[rb251415]

@D@n,

As usual, you are a genius. It took a few tries, but I got it.

Thanks

Royal

Here is the code if anyone is interested...

P1: process(clk, rst, btn_a, on_a)
    begin  
    if rst = '1' and btn_a = '0' then
      on_a <= '0';
    elsif rst = '0' and btn_a = '1' then
      cntra <= (others => '0');
      on_a <= '1';
    elsif (rising_edge(clk) and on_a = '1') then
       cntra <= cntra +1;
       if cntra < 200000000 then
         on_a <= '1';
       else 
         on_a <= '0';
       end if;
    end if;
end process;

[D@n]

@rb251415,

Just a warning, though ... that asynchronous reset is going to bite you, as will asynchronously checking for the button (for the same reason).  I highly recommend you make *everything* in your design dependent upon the positive edge of the clock.

Dan

[rb251415]

@D@n,

Thank you. I will check back through my program and correct them all.