--Editor: Robert Hood
--Group: iOS Remote Control Car
--References: Multi_PWM from www.grigaitis.eu, green_leds.vhd

library altera;
use altera.altera_europa_support_lib.all;

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity pwm is

port(
     
     csi_myclock_clk 	   : in std_logic; --clk is standard for both PWM and Avalon memory slave

     

     csi_myclock_reset	   : in std_logic; --clk reset

     
     avs_pwm_write_n 	   : in std_logic; --write
     avs_pwm_chipselect	   : in std_logic; -- chip select

     avs_pwm_address 	   : in std_logic_vector(1 downto 0); --address

     avs_pwm_readdata 	   : out std_logic_vector(15 downto 0); --Needed for the Avalon interface

     avs_pwm_writedata 	   : in std_logic_vector(15 downto 0); -- Data to be input represents the duty cycle

     coe_pwm_output_export : out std_logic-- Ouput either 1 (high) or 0 (low)	
		
);

end entity;

architecture pwm_control of pwm is

signal pwm_signal : std_logic_vector(19 downto 0); --represents the duty cycle
signal counter : std_logic_vector(19 downto 0) := (others => '0'); -- 20 bit counter
signal read_mux_out :std_logic_vector(19 downto 0);


--Following was manipulated from the green_leds.vhd generated by the SOPC builder


begin
--Create a 20 bit vector from the 16 bit input vector
read_mux_out <= A_REP(to_std_logic((((std_logic_vector'("000000000000000000000000000000") & (avs_pwm_address)) = std_logic_vector'("00000000000000000000000000000000")))), 20) AND pwm_signal;


other_proc:process(csi_myclock_clk,csi_myclock_reset)
begin
   

--if reset than set the duty cycle to '0'

	if csi_myclock_reset= '1' then
      pwm_signal <= (others => '0');
		

   --If reset is not set to '1' and chipselect, write_n and address are the correct values

   -- Then set the duty cycle to the value that was input by the user

	

	 elsif csi_myclock_clk'event and csi_myclock_clk = '1' then
		
		 if std_logic'(((avs_pwm_chipselect AND NOT avs_pwm_write_n) AND to_std_logic((((std_logic_vector'("000000000000000000000000000000") & (avs_pwm_address)) = std_logic_vector'("00000000000000000000000000000000")))))) = '1' then
        pwm_signal <= avs_pwm_writedata(15 DOWNTO 0) & "0000";
      end if;
    end if;

  end process;

--end of code manipulated from green_leds.vhd


clk_proc:process(csi_myclock_clk)
--------Increment the counter

begin



if csi_myclock_reset='1' then

counter <= (others => '0');
 

--At every rising clock edge, increment the counter 


elsif rising_edge(csi_myclock_clk) then
  	counter <= counter +1;
end if;

--Note: In order to get a frequency of 50Hz, which is what the pwm_output to our car needs to be, both for
--steering and motor control, since we use a 50MHz clock, there had to 1,000,000 clock ticks per period. 
--In order to get the required 1,000,000 clock ticks we needed to use a 20 bit counter, however a full 
--20 bit counter would count up to 2,097,152, and since we only wanted it to count to 1,000,000 that is why 
--you see "11110100001001000000" = 1,000,000 , as opposed to all "1's". This gives us

--the proper output frequency of 50Hz.
	
	if(counter = "11110100001001000000") then
	counter <= (others => '0');
	end if;
	
--For as long as the "pwm_signal" value is greater than 0, and greater than the "counter" value, 
--set the "pwm_output" to 1(high)
--Else set "pwm_output" it to 0(low)


if ((pwm_signal>counter) and (pwm_signal>0))
then		   
	coe_pwm_output_export<='1';

			  
else coe_pwm_output_export<='0'; 
end if;


end process clk_proc;


end pwm_control;

--Editor: Robert Hood
--Group: iOS Remote Control Car
--References: Multi_PWM from www.grigaitis.eu, green_leds.vhd