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--------------------------------------------------------------------------

-- Package

--

--

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

package signal_conditioning_pack is

-- Component declarations not provided any more.

-- With VHDL '93 and newer, component declarations are allowed,

-- but not required.

--

-- Please to try direct instantiation instead, for example:

--

--   instance_name : entity work.entity_name(beh)

--

end signal_conditioning_pack;

-------------------------------------------------------------------------------

-- Edge Detector

-------------------------------------------------------------------------------

--

-- Author: John Clayton

-- Date  : Nov.  1, 2013 Started Coding, drawing from various other sources.

--                       Created description.  Simulated it and saw that it

--                       works.

--                 

--

-- Description

-------------------------------------------------------------------------------

-- This module is a super simple edge detector, which produces is high-going

-- pulse whenever there is an edge on the input.  The type of edge is

-- selectable via generic.

--

-- The sys_clk_en affects the operation by extending the length of the pulse

-- output beyond one single sys_clk cycle, as expected.

--

-- Detecting both rising and falling edges is allowed.  Detecting neither is

-- also allowed, but not recommended.

--

-- The sys_rst_n input is an asynchronous reset.

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

  entity edge_detector is

    generic(

      DETECT_RISING  : natural := 1;

      DETECT_FALLING : natural := 0

    );

    port (

      -- System Clock and Clock Enable

      sys_rst_n   : in  std_logic;

      sys_clk     : in  std_logic;

      sys_clk_en  : in  std_logic;

      -- Input Signal

      sig_i       : in  std_logic;

      -- Output pulse

      pulse_o     : out std_logic

    );

  end edge_detector;

architecture beh of edge_detector is

  -- Constants

  -- Functions & associated types

  -- Signal Declarations

  signal sig_r1  : std_logic;

  signal pulse_r : std_logic;

  signal pulse_f : std_logic;

  signal pulse_b : std_logic;

begin

process (sys_clk, sys_rst_n)

begin

  if (sys_rst_n='0') then

    sig_r1 <= '0';

  elsif (sys_clk'event and sys_clk='1') then -- rising edge

    if (sys_clk_en='1') then

      sig_r1 <= sig_i;

    end if;

  end if;

end process;

-- The detection

pulse_r <= '1' when sig_i='1' and sig_r1='0' else '0';

pulse_f <= '1' when sig_i='0' and sig_r1='1' else '0';

pulse_b <= sig_i xor sig_r1;

-- The output

pulse_o <= pulse_b when DETECT_RISING/=0 and DETECT_FALLING/=0 else

           pulse_r when DETECT_RISING/=0 else

           pulse_f when DETECT_FALLING/=0 else

           '0'; -- Haha!  Don't go there!

end beh;

-------------------------------------------------------------------------------

-- Leaky Integrator

-------------------------------------------------------------------------------

--

-- Author: John Clayton

-- Date  : Oct. 11, 2013 Started Coding, drawing from various other sources.

--                       Created description.  Simulated it and saw that it

--                       works.

--         Sep. 20, 2017 Revised delta assignment, to eliminate custom

--                       resize function.

--

-- Description

-------------------------------------------------------------------------------

-- This module is a pretty simple digital "leaky integrator" designed to low

-- pass noisy signals by integrating them.

--

--   The first order differential equation is of the form:

--

--     dx/dt = -leak_factor*x + input

--

-- The input is discretized in both time and amplitude.  A one bit digital

-- input can be mapped to the "input" signal by using a positive value for

-- '1' and a negative value for '0'  Alternately, a signed DSP type signal

-- can be used directly.

--

-- The "leak_factor" is a feedback term, so that "DC gain" is inversely

-- proportional to the leak_factor.

--

-- Due to the presence of the feedback term, the integration's DC value, or

-- constant term, gets "leaked" to zero over time.  This is nice because

-- the threshold centers around zero.

--

-- Hysteresis can be added so that the digital output transitions an amount

-- above or below zero, depending on the current value of the output.

--

-- Clear as mud?  Well, it's similar to a low-pass filter, and the hysteresis

-- also helps remove noise on the input signal.

--

-- The sys_rst_n input is an asynchronous reset.

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

  entity leaky_integrator is

    generic(

      LEAK_FACTOR_BITS : natural := 10;

      LEAK_FACTOR      : natural := 10;

      INTEGRATOR_BITS  : natural := 16   -- Bits in the integrating accumulator

    );

    port (

      -- System Clock and Clock Enable

      sys_rst_n   : in  std_logic;

      sys_clk     : in  std_logic;

      sys_clk_en  : in  std_logic;

      -- Settings

      input       : in  signed(INTEGRATOR_BITS-1 downto 0);

      -- Integration Result

      integrator  : out signed(INTEGRATOR_BITS-1 downto 0)

    );

  end leaky_integrator;

architecture beh of leaky_integrator is

  -- Constants

  -- Functions & associated types

  -- Signal Declarations

  signal sum     : signed(INTEGRATOR_BITS-1 downto 0);

  signal delta   : signed(INTEGRATOR_BITS-1 downto 0);

  signal m_term  : signed(INTEGRATOR_BITS+LEAK_FACTOR_BITS downto 0);

begin

-- The feedback term

m_term <= sum*to_signed(LEAK_FACTOR,LEAK_FACTOR_BITS+1);

-- The difference term

delta  <= input - m_term(m_term'length-1 downto m_term'length-delta'length);

-- The leaky integrator

process (sys_clk, sys_rst_n)

begin

  if (sys_rst_n='0') then

    sum <= to_signed(0,integrator'length);

  elsif (sys_clk'event and sys_clk='1') then -- rising edge

    if (sys_clk_en='1') then

      sum <= sum + delta;

    end if;

  end if;

end process;

-- The outputs

integrator <= sum;

end beh;

-------------------------------------------------------------------------------

-- Leaky Integrator with conditioned Digital Output

-------------------------------------------------------------------------------

--

-- Author: John Clayton

-- Date  : Oct. 11, 2013 Started Coding, drawing from various other sources.

--                       Created description.  Simulated it and saw that it

--                       works.

--         Sep. 20, 2017 Revised delta assignment, to eliminate custom

--                       resize function.

--                 

--

-- Description

-------------------------------------------------------------------------------

-- This module is a pretty simple digital "leaky integrator" designed to clean

-- up noisy repetitive signals by integrating them, and applying thresholds

-- to the integrated result.

--

--   The first order differential equation is of the form:

--

--     dx/dt = -leak_factor*x + input

--

-- The input is discretized in both time and amplitude.  A one bit digital

-- input can be mapped to the "input" signal by using a positive value for

-- '1' and a negative value for '0'

--

-- The "leak_factor" is a feedback term, so that "DC gain" is inversely

-- proportional to the leak_factor.

--

-- Due to the presence of the feedback term, the integration's DC value, or

-- constant term, gets "leaked" to zero over time.  This is nice because

-- the threshold centers around zero.

--

-- Hysteresis can be added so that the digital output transitions an amount

-- above or below zero, depending on the current value of the output.

--

-- Clear as mud?  Well, it's similar to a low-pass filter, and the hysteresis

-- also helps remove noise on the input signal.

--

-- The sys_rst_n input is an asynchronous reset.

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

  entity leaky_integrator_with_digital_output is

    generic(

      FACTOR_BITS     : natural := 10;  -- Make this less than INTEGRATOR_BITS

      HYSTERESIS_BITS : natural := 10;  -- Make this less than INTEGRATOR_BITS

      INTEGRATOR_BITS : natural := 16   -- Bits in the integrating accumulator

    );

    port (

      -- System Clock and Clock Enable

      sys_rst_n   : in  std_logic;

      sys_clk     : in  std_logic;

      sys_clk_en  : in  std_logic;

      -- Settings

      input       : in  signed(INTEGRATOR_BITS-1 downto 0);

      leak_factor : in  signed(FACTOR_BITS-1 downto 0);

      hysteresis  : in  unsigned(HYSTERESIS_BITS-1 downto 0);

      -- Integration Result

      integrator  : out signed(INTEGRATOR_BITS-1 downto 0);

      -- Conditioned Digital Output Signal

      output      : out std_logic

    );

  end leaky_integrator_with_digital_output;

architecture beh of leaky_integrator_with_digital_output is

  -- Constants

  -- Functions & associated types

  -- Signal Declarations

  signal sum     : signed(INTEGRATOR_BITS-1 downto 0);

  signal delta   : signed(INTEGRATOR_BITS-1 downto 0);

  signal m_term  : signed(INTEGRATOR_BITS+FACTOR_BITS-1 downto 0);

  signal out_l   : std_logic;

  signal hp_term : signed(INTEGRATOR_BITS-1 downto 0);

  signal hn_term : signed(INTEGRATOR_BITS-1 downto 0);

begin

-- The feedback term

m_term <= sum*leak_factor;

-- The difference term

delta  <= input - m_term(m_term'length-1 downto m_term'length-delta'length);

-- The leaky integrator

process (sys_clk, sys_rst_n)

begin

  if (sys_rst_n='0') then

    sum <= to_signed(0,integrator'length);

    out_l <= '0';

  elsif (sys_clk'event and sys_clk='1') then -- rising edge

    if (sys_clk_en='1') then

      sum <= sum + delta;

      if (out_l='0') then

        if (sum>hp_term) then

          out_l <= '1';

        end if;

      else

        if (sum<hn_term) then

          out_l <= '0';

        end if;

      end if;

    end if;

  end if;

end process;

-- The hysteresis terms

hp_term <= signed(resize(hysteresis,INTEGRATOR_BITS));

hn_term <= not(hp_term)+1;

-- The outputs

integrator <= sum;

output <= out_l;

end beh;

-------------------------------------------------------------------------------

-- Multi Stage Leaky Integrator with Digital Output

-------------------------------------------------------------------------------

--

-- Author: John Clayton

-- Date  : Oct. 11, 2013 Started Coding, drawing from various other sources.

--                       Created description.

--                 

--

-- Description

-------------------------------------------------------------------------------

-- This module implements N-stages of leaky integrators.  Each stage has the

-- same leak factor, which is a value fixed by generics.  Use powers of two

-- to avoid inferring multipliers.  The smallest value of 1 is actually a

-- pretty nice choice.  The LEAK_FACTOR_BITS generic determines how small

-- the leak factor is by setting the number of bits.  The integer is converted

-- as follows:

--

--   multiplicand = to_signed(LEAK_FACTOR,LEAK_FACTOR_BITS);

--

--   It seems that the smallest signed number is 2 bits wide - one for a sign

--   bit, and the other for magnitude.  So, LEAK_FACTOR_BITS must be >=2.

--   Between stages, an arithmetic shift right operation is inserted, which is

--   intended to automatically scale the signal to fit the next integrator.

--

-- The hysteresis value is only applied at the final stage output, to derive

-- the conditioned digital output signal.

--

-- The "leak_factor" is a feedback term, so that "DC gain" is inversely

-- proportional to the leak_factor.

--

-- Due to the presence of the feedback term, the integration's DC value, or

-- constant term, gets "leaked" to zero over time.  This is nice because

-- the threshold centers around zero.

--

-- Hysteresis can be added so that the digital output transitions an amount

-- above or below zero, depending on the current value of the output.

--

-- Clear as mud?  Well, it's similar to a low-pass filter, and the hysteresis

-- also helps remove noise on the input signal.

--

-- The more stages are used, the more low-pass filtering occurs.

--

-- The sys_rst_n input is an asynchronous reset.

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

library work;

use work.signal_conditioning_pack.all;

  entity multi_stage_leaky_integrator is

    generic(

      STAGES           : natural := 2;

      LEAK_FACTOR_BITS : natural := 5;  -- Inversely related to LP corner frequency. (Min=1)

      HYSTERESIS_BITS  : natural := 8;  -- Make this less than INTEGRATOR_BITS

      INTEGRATOR_BITS  : natural := 16  -- Bits in each integrating accumulator

    );

    port (

      -- System Clock and Clock Enable

      sys_rst_n   : in  std_logic;

      sys_clk     : in  std_logic;

      sys_clk_en  : in  std_logic;

      -- Settings

      input       : in  signed(INTEGRATOR_BITS-1 downto 0);

      hysteresis  : in  unsigned(HYSTERESIS_BITS-1 downto 0);

      -- Final Stage Integration Result

      integrator  : out signed(INTEGRATOR_BITS-1 downto 0);

      -- Conditioned Digital Output Signal

      output      : out std_logic

    );

  end multi_stage_leaky_integrator;

architecture beh of multi_stage_leaky_integrator is

  -- Constants

    -- This value has been found to preserve amplitude between stages,

    -- without appreciable growth or shrinkage of sum levels.

  constant STAGE_ASR   : natural := LEAK_FACTOR_BITS+1;

  constant LEAK_FACTOR : natural := 1;

  -- Functions & associated types

  -- Signal Declarations

  type sum_type is array (natural range STAGES-1 downto 0) of signed(INTEGRATOR_BITS-1 downto 0);

  signal sum_in  : sum_type;

  signal sum_out : sum_type;

  signal out_l   : std_logic;

  signal hp_term : signed(INTEGRATOR_BITS-1 downto 0);

  signal hn_term : signed(INTEGRATOR_BITS-1 downto 0);

begin

----------------------------------------------

leaky_gen : for nvar in 0 to STAGES-1 generate

begin

  lint : entity work.leaky_integrator(beh)

    generic map(

      LEAK_FACTOR_BITS => LEAK_FACTOR_BITS,

      LEAK_FACTOR      => LEAK_FACTOR,

      INTEGRATOR_BITS  => INTEGRATOR_BITS

    )

    port map(

      -- System Clock and Clock Enable

      sys_rst_n   => sys_rst_n,

      sys_clk     => sys_clk,

      sys_clk_en  => sys_clk_en,

      -- Settings

      input       => sum_in(nvar),

      -- Integration Result

      integrator  => sum_out(nvar)

    );

end generate;

sum_in(0) <= input;

sum_gen : for nvar in 1 to STAGES-1 generate

begin

  sum_in(nvar) <= shift_right(sum_out(nvar-1),STAGE_ASR);

end generate;

-- The hysteresis and digital output

process (sys_clk, sys_rst_n)

begin

  if (sys_rst_n='0') then

    out_l <= '0';

  elsif (sys_clk'event and sys_clk='1') then -- rising edge

    if (sys_clk_en='1') then

      if (out_l='0') then

        if (sum_out(STAGES-1)>hp_term) then

          out_l <= '1';

        end if;

      else

        if (sum_out(STAGES-1)<hn_term) then

          out_l <= '0';

        end if;

      end if;

    end if;

  end if;

end process;

-- The hysteresis terms

hp_term <= signed(resize(hysteresis,INTEGRATOR_BITS));

hn_term <= not(hp_term)+1;

-- The outputs

integrator <= sum_out(STAGES-1);

output <= out_l;

end beh;

-------------------------------------------------------------------------------

-- Integrating Pulse Stretcher

-------------------------------------------------------------------------------

--

-- Author: John Clayton

-- Date  : Oct. 24, 2013 Started Coding, drawing from various other sources.

--                       Created description.  Simulated it and saw that it

--                       works.

--                 

--

-- Description

-------------------------------------------------------------------------------

-- This module is a pretty simple digital pulse stretcher.  A high input pulse

-- present for more than MIN_CLKS clock cycles causes the INITIAL_OFFSET value

-- to be loaded into an accumulator.  The accumulator is then incremented by 

-- STRETCH_FACTOR each clock cycle that the input pulse remains high, and is

-- decremented by one for each clock cycle that the input pulse is low.

--

-- The output is driven high whenever the accumulator is positive.

--

-- The output pulse width is given by:

--

--   Tpulse_o = STRETCH_FACTOR*(Tpulse_i-MIN_CLKS) + INITIAL_OFFSET

--

-- The INITIAL_OFFSET can be used to overcome the effects of minimum input

-- pulse filtering.  Also, if a negative value is used for it, then the

-- output pulse is delayed by additional clock cycles beyond the MIN_CLKS

-- of delay already present.  Another use for the INITIAL_OFFSET value is

-- to "bridge together" a train of pulses which might have some jitter.

-- The INITIAL_OFFSET value allows for some slop of jitter to be covered

-- by the extra decay time, so that no "gaps" appear in the output pulse.

--

-- During the decay time, when the output is high, the arrival of a new pulse

-- will cause further charging of the accumulator.  There is no minimum pulse

-- width for this to occur.  The MIN_CLKS only applies to starting the unit

-- from a quiescent state.

--

-- The integrator is a signed quantity, so set INTEGRATOR_BITS accordingly,

-- because the integrator can only hold positive quantities up to

-- 2^(INTEGRATOR_BITS-1)-1.

--

-- The sys_rst_n input is an asynchronous reset.

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

use IEEE.MATH_REAL.ALL;

library work;

use work.function_pack.all;

  entity integrating_pulse_stretcher is

    generic(

      MIN_CLKS        : natural :=  5; -- pulses below this many clocks are ignored

      RETRIGGERABLE   : natural :=  1; -- 1=restart on new pulses.  0=decay to zero before restarting

      STRETCH_FACTOR  : natural :=  2; -- 0=no output, 1=same size, 2=double

      INITIAL_OFFSET  : natural := 25; -- Value initially loaded into integrator

      INTEGRATOR_BITS : natural := 16  -- Bits in the integrating accumulator

    );

    port (

      -- System Clock and Clock Enable

      sys_rst_n   : in  std_logic;

      sys_clk     : in  std_logic;

      sys_clk_en  : in  std_logic;

      -- Input

      pulse_i     : in  std_logic;

      -- Output

      pulse_o     : out std_logic

    );

  end integrating_pulse_stretcher;

architecture beh of integrating_pulse_stretcher is

  -- Constants

  constant RUNT_BITS : natural := timer_width(MIN_CLKS);

  -- Functions & associated types

  -- Signal Declarations

  signal runt_count : unsigned(RUNT_BITS-1 downto 0);

  signal sum        : signed(INTEGRATOR_BITS-1 downto 0);

  signal pulse_i_r1 : std_logic;

  signal pulse_l    : std_logic;

begin

-- The integrator

process (sys_clk, sys_rst_n)

begin

  if (sys_rst_n='0') then

    runt_count <= to_unsigned(0,runt_count'length);

    sum        <= to_signed(0,sum'length);

    pulse_i_r1 <= '0';

  elsif (sys_clk'event and sys_clk='1') then -- rising edge

    if (sys_clk_en='1') then

      -- Detect rising edge of input pulse

      pulse_i_r1 <= pulse_i;

      -- When the pulse_i input is consecutively high, decrement the runt

      -- counter until it is zero.

      if (runt_count>0) then

        if (pulse_i='1') then

          runt_count <= runt_count-1;

        else

          runt_count <= to_unsigned(MIN_CLKS,runt_count'length);

        end if;

      end if;

      -- Trigger on rising edge of pulse_i

      if (pulse_i='1' and pulse_i_r1='0') then

        if (pulse_l='0' or (RETRIGGERABLE=1 and pulse_l='1')) then

          runt_count <= to_unsigned(MIN_CLKS,runt_count'length);

        end if;

      end if;

      -- Load initial offset into accumulator on final runt countdown

      if (runt_count=1) then

        sum <= to_signed(INITIAL_OFFSET,sum'length);

      end if;

      -- Either accumulate or decay, depending on input state

      if (pulse_i='1' and runt_count=0) then

        sum <= sum+STRETCH_FACTOR;

      elsif (pulse_i='0' and pulse_l='1') then

        sum <= sum-1;

      end if;

    end if;

  end if;

end process;

-- The output

pulse_l <= '1' when (sum>0) else '0';

pulse_o <= pulse_l;

end beh;