-- Tyler Lutz; July 26, 2011; 
-- Height of Pulse Peak calculator;
--Input->digital signal from ASIC, time from onboard clock;
--Output->height in volts of peak (optionally also time of peak);

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

library ieee;
use ieee.std_logic_1164.all;

entity fitting_etc_peak 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;
	 OPEAK: out std_logic_vector (0 to 11);        --Dedicated output for peak of pulse
	end fitting_etc_peak;  

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

architecture Herjolfssen7 of fitting_etc_peak 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 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 letop: integer:=0;
   variable peak: integer:=0;                -- height of the peak
    variable peaktime: integer:=0;            --time at which peak occurs


    
-- ==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;
	

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):=14;           --specify desired threshold values for multithreshold claculations
			multithreshold(1):=15;
			multithreshold(2):=17;
			
			
			if (pulsar<multithreshold(0) and pulsarsave(0)/=pulsar)then     --shut up output (supposing there is some) if pulse changes
          	for s in 0 to 11 loop
		           OPEAK(s)<='0';
		       end loop;                 
	     end if;
			

				for k in savescope+2 downto 1 loop      	--pulse saver, for use in averaging and delaying pulse

					pulsarsave(k):=pulsarsave(k-1);            --shift data over one bin in pulsarsave
				end loop;
 
				 pulsarsave(0):=pulsar;								              --stick new incoming data in bin 0
				 
---- 
					
--	-->>))]|[((<< (([|])) >>))]|[((<< (([|]) >>))]|[((<< (([|])) >>))]|[((<< (([|])) >>))]|[((<< (([|])) >>))]|[((<<--

	
	if pulsar>=multithreshold(0) then								--PEAK FINDER
		
		if pulsar>=peak then                   --find largest pulsar
			peak:=pulsar;                       --and store it in "peak"
			peaktime:=accsec;
		end if;
	end if;
	
		if pulsar<multithreshold(0) and pulsarsave(1)>=multithreshold(0) and peak/=0 then       --when pulse goes below 1st threshold
		  for y in 7 downto 0 loop                              --readout in parallel
		      		if peak>=(2**y) then
		         			OPEAK(y)<='1'; 
		        				peak:=peak-2**y;			    --automatically reinitializes 'peak' to zero!!!
		      		else
		      	  	  OPEAK(y)<='0';
						if y=0 then
							peak:=0;
						end if;
						
	     		  	end if;	
	     		  		
	     	end loop;
		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--<< --

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