-- Tyler Lutz; July 26, 2011; 
-- Baseline averager operation;
--Input->digital signal from ASIC, time from onboard clock;
--Output->zero when signal is above threshold, average of last (savescope) # of data points if else;

-------------------------------------------------------------------------
--((o))--((o))--((o))--((o))--((o))--((o))--((o))--((o))--((o))--((o))--
-------------------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;

entity fitting_etc_BLA is
port(	pulse: in std_logic_vector (0 to 11);						--assumed that ASIC readout is in parallel(?), and if not it is easy to parallelize serial input
		clk: in std_logic;
	 OBLA: out std_logic_vector (0 to 11);         --Output baseline average
end fitting_etc_BLA;  

-- ==I==I==I==I==I==I==I==I==I==I==I== --

architecture Herjolfssen7 of fitting_etc_BLA is					

	begin
  
    process(clk)
	variable accsec: integer :=0;										--"seconds" or any other arbitrary time unit, to be adjusted based on the frequency of clock used.
		type gaul is array(natural range <>) of integer;		--define unconstrained array type
	variable pulsebit: gaul (0 to 11);									--pulse is converted later to an integer for calculation purposes; this is an intermediate step
	variable multithreshold: gaul (0 to 2);							--stores our three constant threshold values for the multithresh mode
	
    variable baselineaverage: integer:=0;     -- outputs to OBLA (Output Base Line Average)
    variable pulsesum: integer :=0;                --for baseline averager, stores sum of non-important background data
		variable pulsar: integer:=0;									-- intergized value of incoming pulse
		constant savescope: integer:=100;							--scope size of CFD delay memory and base line averager (here, last 1000 data points)
   --	variable pulsarsave: gaul (0 to savescope+4);							--allows us to delay the pulse (the 10^10 is totally arbitrary)
		variable pulsarbasesave: gaul (0 to savescope+4);     --memory of last savescope non-pulse reading heights
variable letop: integer:=0;
		variable time1: integer:=0;                 --in integral calculator, time of first threshold crossing
		variable time2: integer:=0;               --"                     " time of falling below threshold
		constant delay: integer:=4;              --delay length for CFD (150-200 ps = 4 using our clock specs (see testbench))
		variable eventprint: gaul (0 to 4);							--array output, listing arrival time against event number
    variable eventprintread: gaul (0 to 3);   --"scratchpaper" variable
	  variable basecounter: integer:=0;         --numbers the initial data for early baseline averaging
    variable signalmean: integer:=0;          --for calculating number of electrons
--    variable standarddev: integer:=0;         -- standard deviation of baseline
--    variable standarddevsum: integer:=0;      -- a running sum of stored baseline data (last savescope # of points) minus baseline mean all squared
--   variable peakdeviation: integer:=0;       --largest deviation from mean of baseline
--    variable significance: integer:=0;        --largest deviation of baseline devided by its standard deviation
--    variable squirt: integer:=0;              --a dummy variable whihc facilitates square root calculation using a continued fraction algorithm

--    variable sumcounter: integer:=0;
    
-- ==I==I==I==I==I==I==I==I==I==I==I== --

	begin

	if clk'event and clk='1' then      --program loops at clock rising edge 
	
letop:=(letop+1)mod 50;--1000000;  --slow down clock to 10MHz
	
if letop=0 then

	 
	            
accsec:=(accsec+1) mod 2**12;      --our stopwatch
	
	                         --our oscilloscope data is converted to decimal stored in 'pulsar'
		for j in 0 to 11 loop				-- intigerizing the input pulse; logic vector to binary array to integer(pulsar)
				if pulse(j)='0' then
			pulsebit(j):=1;                --binary array
				elsif pulse(j)='1' then
			pulsebit(j):=0;
				end if;	
				if j=0 then	
				  pulsar:=pulsebit(0);      --a clever way to reinitialize the summand 'pulsar'
				else
				  pulsar:= pulsar+(pulsebit(j))*(2**(j));  --actual binary to integer conversion
				end if;
		end loop;


		
		  multithreshold(0):=5;           --specify desired threshold values for multithreshold claculations
			multithreshold(1):=36;
			multithreshold(2):=37;
			
		
			 
		  if pulsar<multithreshold(0) then      --SAVE DATA POINTS IN ARRAY FOR AVERAGING PURPOSES
	basecounter:=basecounter+1;                     --counts the baseline data by assigning each data point a cardinal number
  
        for m in (savescope+2) downto 1 loop        --flesh out the storage array
          pulsarbasesave(m):=pulsarbasesave(m-1);
        end loop;
  
  pulsarbasesave(0):=pulsar;								       --store baseline output in array
      end if;
				 
---- 

-- >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< --

if pulsar<multithreshold(0) then       						--BASELINE AVERAGER
  
  if sumcounter<=savescope+2 then
   pulsesum:=pulsesum+pulsar;         --running sum of all inputs
   sumcounter:=sumcounter+1;
   baselineaverage:=pulsesum/sumcounter;   --definition of running average
  elsif sumcounter>savescope+2 then       --averaging too many data points becomes untenable => only consider stored points, not all prior points
    pulsesum:= pulsesum+pulsarbasesave(0)-pulsarbasesave(savescope+1);   --include latest data point, let an old one fall out the back end
    baselineaverage:=pulsesum/savescope;      --definition of average over savescope data points
  end if;
  
   	signalmean:=baselineaverage;                             --store for later
			
else
		signalmean:=0;
		baselineaverage:=0;
end if;
  
  				for w in 11 downto 0 loop                              --readout in parallel
		      		if baselineaverage>=(2**w) then                    --...
		         			OBLA(w)<='0'; 
		        				baselineaverage:=baselineaverage-2**w;			
		      		else
		      	  	  OBLA(w)<='1';
	     		  	end if;
	     	end loop;

-- >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< >>--0--O--o--+--o--O--0--<< --


	 end if;	         
end if;	 
  end process;
end Herjolfssen7;