library ieee;
	use ieee.std_logic_1164.all;
	use ieee.numeric_std.all;													-- Worlds longest and most stupid oled controller

entity OLED_DISPLAY is
    Port (
			reset_n			: in	std_logic;
			clk_50			: in 	std_logic;
			ascii_valid		: in	std_logic;
			v_ascii_tdata	: in	std_logic_vector(24 downto 0); 		-- 8bits of ascii code contaning temp
			v_ascii_hdata	: in	std_logic_vector(23 downto 0); 		--	8bits of ascii code contaning humidity
			RW					: out	std_logic;									--	Read/Write select signal, R/W=1: Read R/W: =0: Write
			Strobe			: out std_logic; 									--	Same as E, name used from the ARM course (Operation enable signal. Falling edge triggered.)
			RS					: out std_logic;									--	Register select signal. RS=0: Command, RS=1: Data
			Data_OLED		: out std_logic_vector(7 downto 0));
end OLED_DISPLAY;

architecture rtl of OLED_DISPLAY is

	type t_oled_init_state is (S_idle,
										S_function_set,							--	Function Set: 		001110xx
										S_display_off,								--	Display OFF:		000010xx
										S_display_clear,							--	Display Clear:		00000001
										S_entry_mode_set,							--	Entry Mode Set:	00000110
										S_home_command,							--	Home Command:		00000010
										S_display_on,								--	Display ON:			000011xx
										S_toggle_strobe);

	type t_text_print_state	is (S_idle,										-- Prints the static text
										 S_upper_colon_address,
										 S_upper_colon_data,
										 S_lower_colon_address,
										 S_lower_colon_data,
										 S_numb_celsius_sign_adress,
										 S_numb_celsius_sign_data,
										 S_numb_c_address,
										 S_numb_c_data,
										 S_numb_procent_address,
										 S_numb_procent_data,
										 S_toggle_strobe);

	type t_oled_control_state is (S_idle,									-- Updates the ascii values
											S_temp_address_tens,
											S_temp_data_tens,
											S_temp_address_ones,
											S_temp_data_ones,
											S_temp_address_fraction,
											S_temp_data_fraction,
											S_humid_address_tens,
											S_humid_data_tens,
											S_humid_address_ones,
											S_humid_data_ones,
											S_humid_address_fraction,
											S_humid_data_fraction,
											S_numb_negative_address,
											S_numb_negative_data,
											S_toggle_strobe);

	constant c_cnt_delay600us  : integer := 30000-1;
	constant c_cnt_delay2ms 	: integer := 100000-1;
	constant c_cnt_delayStrobe : integer := 43-1;						-- A bit longer E signal then needed
	constant c_cnt_delay100ms	: integer := 5000000;

	signal long_counter			: integer range 0 to c_cnt_delay100ms;
	signal counter 				: integer range 0 to c_cnt_delay2ms;
	signal flag_init_busy		: std_logic;								-- Flag for "init phase", including the static text printing phase
	signal flag_print_start		: std_logic;								-- Short flag for starting the "print phase"
	signal print_state			: t_text_print_state;
	signal next_print_state		: t_text_print_state;
	signal next_state 			: t_oled_init_state;
	signal init_state   			: t_oled_init_state;
	signal next_ctr_state		: t_oled_control_state;
	signal control_state 		: t_oled_control_state;
	signal tick600us		      : std_logic;								-- Mainly used for overview in sim
	signal tick2ms					: std_logic;								-- Mainly used for overview in sim

begin

p_oled_state :	process(clk_50)
begin

	if rising_edge(clk_50) then

		tick600us 			<= '0';
		tick2ms 				<= '0';

		case init_state is
			when S_idle	=>

				if flag_init_busy = '1' then
					if counter = c_cnt_delay2ms then
							tick2ms 		<= '1';
							counter 		<=  0;

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_function_set;
						else
							counter	<= counter + 1;
						end if;
				end if;

			when S_function_set	=>												--	Function Set: Western European font

						if counter = c_cnt_delay600us then
							counter 		<= 0;
							RS 	 		<= '0';
							RW 			<= '0';

							tick600us 	<= '1';
							counter 		<=  0;

							Strobe 		<= '1';
							Data_OLED 	<= "00111001";

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_display_off;
						else
							counter	<= counter + 1;
						end if;

			when S_display_off	=>												--	Display OFF: No cursor, no blinking

						if counter = c_cnt_delay600us then
							tick600us 	<= '1';
							counter 		<=  0;

							Strobe		<= '1';
							Data_OLED 	<= "00001000";

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_display_clear;
						else
							counter	<= counter + 1;
						end if;

			when S_display_clear =>

						if counter = c_cnt_delay600us then
							tick600us 	<= '1';
							counter 		<=  0;

							Strobe 		<= '1';
							Data_OLED 	<= "00000001";

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_entry_mode_set;
						else
							counter	<= counter + 1;
						end if;

			when S_entry_mode_set =>

						if counter = c_cnt_delay2ms then
							tick2ms 		<= '1';
							counter 		<=  0;

							Strobe 		<= '1';
							Data_OLED 	<= "00000110";

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_home_command;
						else
							counter	<= counter + 1;
						end if;

			when S_home_command =>

						if counter = c_cnt_delay600us then
							tick600us 	<= '1';
							counter 		<=  0;

							Strobe 		<= '1';
							Data_OLED 	<= "00000010";

							init_state 	<= S_toggle_strobe;
							next_state 	<= S_display_on;
						else
							counter	<= counter + 1;
						end if;

			when S_display_on =>													--	Display ON:	No cursor, no blinking

						if counter = c_cnt_delay600us then
							tick600us 			<= '1';
							counter 				<=  0;

							Strobe 				<= '1';
							Data_OLED 			<= "00001100";
							flag_print_start 	<= '1';

							init_state 			<= S_toggle_strobe;
							next_state 			<= S_idle;
						else
							counter	<= counter + 1;
						end if;

			when S_toggle_strobe =>

						if counter = c_cnt_delayStrobe then
							Strobe		<= '0';
							counter 	 	<= 0;
							init_state 	<= next_state;
						else
							counter 	<= counter + 1;
						end if;

			when others =>
				init_state <= S_idle;
		end case;

---------------------------------------------------------------------- Starts printing the "static" chars

		case print_state is
			when S_idle	=>

				if flag_print_start = '1' then
					flag_print_start 	<= '0';
					print_state 		<= S_upper_colon_address;
				end if;

			when S_upper_colon_address	=>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '0';
					Strobe 				<= '1';
					Data_OLED			<= "10000011"; --ADDRESS 03

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_upper_colon_data;
				else
					counter	<= counter + 1;
				end if;


			when S_upper_colon_data	=>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '1';
					Strobe 				<= '1';
					Data_OLED			<= "00101110"; --ASCII code for ","

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_lower_colon_address;
				else
					counter	<= counter + 1;
				end if;


			when S_lower_colon_address =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '0';
					Strobe 				<= '1';
					Data_OLED			<= "11000011"; --ADDRESS 03

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_lower_colon_data;
				else
					counter	<= counter + 1;
				end if;


			when S_lower_colon_data =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '1';
					Strobe 				<= '1';
					Data_OLED			<= "00101110"; --ASCII code for ","

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_celsius_sign_adress;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_celsius_sign_adress =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '0';
					Strobe 				<= '1';
					Data_OLED			<= "11000101"; --ADDRESS 44

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_celsius_sign_data;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_celsius_sign_data =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '1';
					Strobe 				<= '1';
					Data_OLED			<= "11010010"; --ASCII code for "*"

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_c_address;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_c_address =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '0';
					Strobe 				<= '1';
					Data_OLED			<= "10000101"; --ADDRESS 05

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_c_data;
				else
					counter	<= counter + 1;
				end if;


			when S_numb_c_data =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '1';
					Strobe 				<= '1';
					Data_OLED			<= "01000011";	--ASCII code for "C"

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_procent_address;
				else
					counter	<= counter + 1;
				end if;


			when S_numb_procent_address =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '0';
					Strobe 				<= '1';
					Data_OLED			<= "11000101"; --ADDRESS 45

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_numb_procent_data;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_procent_data =>

				if counter = c_cnt_delay600us then
					tick600us 			<= '1';
					counter 				<=  0;

					RS 					<= '1';
					Strobe 				<= '1';
					Data_OLED			<= "00100101"; --Data for "%" sign
					flag_init_busy 	<= '0';

					print_state  		<= S_toggle_strobe;
					next_print_state 	<= S_idle;
				else
					counter    	<= counter + 1;
				end if;

			when S_toggle_strobe =>

				if counter = c_cnt_delayStrobe then
					Strobe			<= '0';
					counter 			<= 0;
					print_state 	<= next_print_state;
				else
					counter 	<= counter + 1;
				end if;

			when others =>
				init_state <= S_idle;
		end case;

-------------------------------------------------------------------	Update state for the humidity and temp data
		case control_state is

			when S_idle =>
				if flag_init_busy = '0' then
					if long_counter = c_cnt_delay100ms then
						control_state <= S_temp_address_tens;
					else
						long_counter <= long_counter + 1;
					end if;
				end if;

			when S_temp_address_tens =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "10000001"; --ADDRESS 01 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_temp_data_tens;
				else
					counter	<= counter + 1;
				end if;

			when S_temp_data_tens =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_tdata(23 downto 16); --Data for the "tens" off the temp data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_temp_address_ones;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_temp_address_ones =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "10000010"; --ADDRESS 02 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_temp_data_ones;
				else
					counter	<= counter + 1;
				end if;

			when S_temp_data_ones =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<= 0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_tdata(15 downto 8); --Data for the "ones" off temp data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_temp_address_fraction;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_temp_address_fraction =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<= 0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "10000100"; --ADDRESS 04 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_temp_data_fraction;
				else
					counter	<= counter + 1;
				end if;

			when S_temp_data_fraction =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_tdata(7 downto 0); --Data for the "fraction" off the temp data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_humid_address_tens;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_address_tens =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "11000001"; --ADDRESS 41 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_humid_data_tens;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_data_tens =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_hdata(23 downto 16); --Data for the "tens" off the humidity data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_humid_address_ones;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_address_ones =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<= 0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "11000011"; --ADDRESS 43 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_humid_data_ones;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_data_ones =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_hdata(15 downto 8); --Data for the "ones" off the humidity data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_humid_address_fraction;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_address_fraction =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "11000100"; --ADDRESS 44 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_humid_data_fraction;
				else
					counter	<= counter + 1;
				end if;

			when S_humid_data_fraction =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= v_ascii_hdata(7 downto 0); --Data for the "fraction" off the humidity data

						control_state  <= S_toggle_strobe;
						next_ctr_state <= S_numb_negative_address;
					end if;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_negative_address =>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					RS 				<= '0';
					Strobe 			<= '1';
					Data_OLED		<= "10000000"; --ADDRESS 00 on the oled

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_numb_negative_data;
				else
					counter	<= counter + 1;
				end if;

			when S_numb_negative_data	=>

				if counter = c_cnt_delay600us then
					tick600us 		<= '1';
					counter 			<=  0;

					if ascii_valid = '1' then
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= "00101101"; --negative sign
					else
						RS 				<= '1';
						Strobe 			<= '1';
						Data_OLED		<= "11111110"; -- empty sign
					end if;

					control_state  <= S_toggle_strobe;
					next_ctr_state <= S_temp_address_tens;
				else
					counter	<= counter + 1;
				end if;

			when S_toggle_strobe =>

				if counter = c_cnt_delayStrobe then
					Strobe			<= '0';
					counter 			<= 0;
					control_state 	<= next_ctr_state;
				else
					counter	<= counter + 1;
				end if;

			when others =>
				control_state <= S_idle;

		end case;
	end if;

	if reset_n = '0' then
		Data_OLED <= (others => '0');
		RS 		 			<= '0';
		RW 					<= '0';
		Strobe 	 			<= '0';
		flag_print_start 	<= '0';
		flag_init_busy 	<= '1';
		print_state			<= S_idle;
		control_state 		<= S_idle;
		init_state 	  		<= S_idle;
	end if;

end process p_oled_state;
end architecture rtl;