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Improved documentation of all vhd modules except testbenches and lcd driver

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This commit is contained in:
T-moe
2016-06-19 15:58:29 +02:00
parent 78ea176aac
commit f5f862c044
4 changed files with 163 additions and 142 deletions
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159
controller.vhd
View File

@@ -25,44 +25,47 @@ entity controller is
end controller;
architecture Behavioral of controller is
type states is(S_WAIT,
-- FSM with the following states:
type states is(S_WAIT, -- wait till the lcd is no longer busy, and returns in a specific state afterwards
S_FORM_PREF, -- prints the form prefix ("Form:")
S_FREQ_PREF, -- frequenz prefix ("Freq: 00000 Hz")
S_FORM_CONT, -- form content ("Rechteck, Sinus...")
S_FREQ_CONT, -- frequenz content ("-----")
S_IDLE );
S_IDLE ); -- controller is idle and waits on user input
signal state_reg, state_next : states := S_WAIT;
signal ret_state_reg, ret_state_next: states := S_FORM_PREF;
signal state_reg, state_next : states := S_WAIT; -- Current State
signal ret_state_reg, ret_state_next: states := S_FORM_PREF; -- State to return to, after S_WAIT
----- Edge detection registers -----
signal btn_old_reg, btn_old_next : std_logic := '0';
signal enc_old_reg, enc_old_next: std_logic :='0';
signal busy_old_reg, busy_old_next : std_logic := '0';
signal form_old_reg, form_old_next : unsigned (1 downto 0) := (others => '0');
--digitnr which is currently edited 0-4
signal digpos_reg, digpos_next : unsigned(2 downto 0) := (others => '0');
signal charcnt_reg, charcnt_next : unsigned(3 downto 0) := (others => '0');
-- array 5x 4bit(0-9)
signal digpos_reg, digpos_next : unsigned(2 downto 0) := (others => '0'); -- digitnr which is currently edited 0-4
signal charcnt_reg, charcnt_next : unsigned(3 downto 0) := (others => '0'); -- character number which is currently being written out
-- Decimal value (0-9) of the sigle frequency digits (array 5x 4bit)
type storage_digit is array (0 to 7) of unsigned (3 downto 0);
signal digit_reg, digit_next : storage_digit := (others => (others => '0'));
signal lcd_newchar_reg,lcd_newchar_next : std_logic := '0';
signal lcd_newpos_reg,lcd_newpos_next : std_logic := '0';
signal lcd_data_reg, lcd_data_next: unsigned(7 downto 0) :=(others => '0');
signal lcd_newchar_reg,lcd_newchar_next : std_logic := '0'; -- Register for the LCD Newchar signal
signal lcd_newpos_reg,lcd_newpos_next : std_logic := '0'; -- Register for the LCD Newpos signal
signal lcd_data_reg, lcd_data_next: unsigned(7 downto 0) :=(others => '0'); -- Register for the LCD Databus signal
signal freq_out_reg, freq_out_next : unsigned (16 downto 0) := (others => '0');
signal freq_out_reg, freq_out_next : unsigned (16 downto 0) := (others => '0'); -- Register for the frequency ouput (in hz)
----------------Constants---------------------------------
-- Signal Form Prefix:
type character_array_short is array (0 to 7) of character;
constant str_form_pref : character_array_short := ( 'F', 'o', 'r','m',':', others => ' ' );
-- Signal Frequency Prefix/Postfix:
type character_array_long is array (0 to 15) of character;
constant str_freq_pref : character_array_long := ( 'F', 'r', 'e','q',':',' ','0','0','0','0','0',' ','H','z', others => ' ' );
-- Signal Form names:
type character_form_array is array (0 to 3, 0 to 7) of character;
constant str_form : character_form_array := (
('S','q','u','a','r','e',' ',' '),
@@ -71,9 +74,11 @@ architecture Behavioral of controller is
('S','i','n','e',' ',' ',' ',' ')
);
-- Possible improvement: Write a helper function which initializes those character arrays from a string
begin
-- State register process (sequential)
proc1: process(clk,rst)
begin
if(rst='1') then
@@ -82,7 +87,6 @@ begin
btn_old_reg <= '0';
enc_old_reg <='0';
busy_old_reg <= '0';
form_old_reg <= "00";
charcnt_reg <= (others => '0');
@@ -92,6 +96,7 @@ begin
freq_out_reg <=(others => '0');
-- On reset: wait on display startup and then start with S_FORM_PREF state
state_reg <= S_WAIT;
ret_state_reg <= S_FORM_PREF;
@@ -101,7 +106,6 @@ begin
btn_old_reg <= btn_old_next;
enc_old_reg <= enc_old_next;
busy_old_reg <= busy_old_next;
form_old_reg <= form_old_next;
charcnt_reg <= charcnt_next;
@@ -117,143 +121,142 @@ begin
end if;
end process proc1;
freq_out <= freq_out_reg;
lcd_data <= lcd_data_reg;
lcd_newchar <= lcd_newchar_reg;
lcd_newpos <= lcd_newpos_reg;
NSL: process(digit_reg,enc_right,enc_ce,enc_btn,digpos_reg,btn_old_reg, charcnt_reg, lcd_busy, lcd_data_reg, busy_old_reg, state_reg, ret_state_reg, enc_ce,enc_old_reg, form_old_reg, form)
-- Next State logic process (combinational)
NSL: process(digit_reg,enc_right,enc_ce,enc_btn,digpos_reg,btn_old_reg, charcnt_reg, lcd_busy, lcd_data_reg, state_reg, ret_state_reg, enc_ce,enc_old_reg, form_old_reg, form)
begin
-- To avoid latches the most signals are assigned with their previous value (Exceptions marked)
digit_next <= digit_reg;
digpos_next <= digpos_reg;
busy_old_next <= lcd_busy;
btn_old_next <= btn_old_reg;
enc_old_next <= enc_old_reg;
form_old_next <= form_old_reg;
charcnt_next <= charcnt_reg;
lcd_newchar_next <= '0';
lcd_newpos_next <= '0';
lcd_newchar_next <= '0'; -- next newchar is always 0, becasue normally we dont want to send anything
lcd_newpos_next <= '0'; -- same for newpos
lcd_data_next <= lcd_data_reg;
state_next <= state_reg;
ret_state_next <= ret_state_reg;
-- The next statement produces two warnings which can be safely ignored:
-- xst:643 - The result of a <...>-bit multiplication is partially used...
freq_out_next <= resize(
resize(digit_reg(0), 4)
-- Put together the frequency as a 17 bit vector (in hz) out of the single decimal places
freq_out_next <= resize( resize(digit_reg(0), 4)
+ resize(digit_reg(1) ,4)* 10
+ resize(digit_reg(2) ,7)* 100
+ resize(digit_reg(3) ,10) * 1000
+ resize(digit_reg(4) ,14) * 10000
, 17);
,17);
case state_reg is
when S_WAIT => -- switch on current state
if(lcd_busy = '0' and busy_old_reg ='1' ) then
state_next<= ret_state_reg;
case state_reg is -- switch on current state
when S_WAIT => -- lcd is currently busy
if(lcd_busy = '0') then --lcd is no longer busy
state_next<= ret_state_reg; -- return to state given by ret_state
end if;
when S_FORM_PREF =>
state_next <= S_WAIT;
if(charcnt_reg < 7 ) then
charcnt_next <= charcnt_reg + 1;
ret_state_next <= S_FORM_PREF;
when S_FORM_PREF => -- print the form prefix
state_next <= S_WAIT; -- always wait for lcd_busy=0 after this state
if(charcnt_reg < 7 ) then -- not 8 characters written yet: Send characters
charcnt_next <= charcnt_reg + 1; -- increase character position
ret_state_next <= S_FORM_PREF; -- return into this state after wait
-- Output current character (Multiplexer). Implemented as an array lookup with cast from character to ascii value
lcd_data_next <= to_unsigned(character'pos(str_form_pref(to_integer(resize(charcnt_reg,3)))),8);
lcd_newchar_next <= '1';
else
charcnt_next <= (others => '0');
lcd_data_next <= x"40"; --Start adress for line 2
lcd_newpos_next <= '1';
ret_state_next <= S_FREQ_PREF;
lcd_newchar_next <= '1'; -- signal the lcd driver that a new character is ready for writing
else -- all 8 characters written: Change adress to line 2 (as preparation for S_FREQ_PREF)
charcnt_next <= (others => '0'); -- reset charcnt
lcd_data_next <= x"40"; -- Start adress for line 2
lcd_newpos_next <= '1'; -- signal the lcd driver that a new position is available
ret_state_next <= S_FREQ_PREF; -- continue with S_FREQ_PREF state
end if;
when S_FREQ_PREF =>
if(charcnt_reg < 15 ) then
when S_FREQ_PREF => -- print the frequency prefix/postfix
if(charcnt_reg < 15 ) then -- not all 16 characters written yet
charcnt_next <= charcnt_reg + 1;
state_next <= S_WAIT;
ret_state_next <= S_FREQ_PREF;
lcd_data_next <= to_unsigned(character'pos(str_freq_pref(to_integer(charcnt_reg))),8);
lcd_newchar_next <= '1';
else
else -- all charcters written
charcnt_next <= (others => '0');
state_next <= S_FORM_CONT;
state_next <= S_FORM_CONT; -- print the Form content now
end if;
when S_FORM_CONT =>
when S_FORM_CONT => -- print the form content
state_next <= S_WAIT;
ret_state_next <= S_FORM_CONT;
charcnt_next <= charcnt_reg + 1;
if(charcnt_reg < 1 ) then
lcd_data_next <= x"06"; --adress character 7 on line 1
if(charcnt_reg < 1 ) then -- Step 1: Set address
lcd_data_next <= x"06"; -- adress character 7 on line 1
lcd_newpos_next <= '1';
elsif(charcnt_reg < 9) then
elsif(charcnt_reg < 9) then -- Step 2 (8x): Print a character of the form
lcd_data_next <= to_unsigned(character'pos(str_form(to_integer(form),to_integer(resize(charcnt_reg-1,3)))),8);
lcd_newchar_next <= '1';
else
else -- Step 3: Set adress/cursor back to current digit
charcnt_next <= (others => '0');
lcd_data_next <= x"4A" - digpos_reg; -- adress character 11 on line 2 - digit position
lcd_newpos_next <= '1';
ret_state_next <= S_IDLE;
end if;
when S_FREQ_CONT =>
when S_FREQ_CONT => -- print the frequency content
state_next <= S_WAIT;
if(charcnt_reg < 1 ) then
if(charcnt_reg < 1 ) then -- Step 1: Set address for current digit
charcnt_next <= charcnt_reg + 1;
ret_state_next <= S_FREQ_CONT;
lcd_data_next <= x"4A" - digpos_reg; -- adress character 11 on line 2 - digit position
lcd_newpos_next <= '1';
elsif(charcnt_reg = 1) then
elsif(charcnt_reg = 1) then -- Step 2: Print current digit
charcnt_next <= charcnt_reg + 1;
ret_state_next <= S_FREQ_CONT;
lcd_data_next <= to_unsigned(character'pos('0'),8) + digit_reg(to_integer(digpos_reg));
lcd_newchar_next <= '1';
else
else -- Step 3: Reset adress/cursor back to current digit (auto increment of display cannot be disabled)
ret_state_next <= S_IDLE;
charcnt_next <= (others => '0');
lcd_data_next <= x"4A" - digpos_reg; -- adress character 11 on line 2 - digit position
lcd_newpos_next <= '1';
end if;
when S_IDLE =>
when S_IDLE => -- Controller is idle and wait on user input
-- Update edge dectection helper registers:
btn_old_next <= enc_btn;
enc_old_next <= enc_ce;
form_old_next <= form;
if(form /= form_old_reg) then
state_next <= S_FORM_CONT;
elsif(enc_ce='1' and enc_old_reg ='0') then
if(enc_right='1') then
if(digit_reg(to_integer(digpos_reg)) = to_unsigned(9,4)) then
digit_next(to_integer(digpos_reg)) <= to_unsigned(0,4);
else
digit_next(to_integer(digpos_reg)) <= digit_reg(to_integer(digpos_reg)) + 1;
if(form /= form_old_reg) then -- form changed
state_next <= S_FORM_CONT; -- print form
elsif(enc_ce='1' and enc_old_reg ='0') then -- positive egde on encoder clock enable
if(enc_right='1') then -- encoder was turned right
if(digit_reg(to_integer(digpos_reg)) = to_unsigned(9,4)) then -- digit value = 9
digit_next(to_integer(digpos_reg)) <= to_unsigned(0,4); -- set digit value to 0
else -- digit value < 9
digit_next(to_integer(digpos_reg)) <= digit_reg(to_integer(digpos_reg)) + 1; -- increase digit value
end if;
else
if(digit_reg(to_integer(digpos_reg)) = to_unsigned(0,4)) then
digit_next(to_integer(digpos_reg)) <= to_unsigned(9,4);
else
digit_next(to_integer(digpos_reg)) <= digit_reg(to_integer(digpos_reg)) -1;
else -- encoder was turned left
if(digit_reg(to_integer(digpos_reg)) = to_unsigned(0,4)) then -- digit value = 0
digit_next(to_integer(digpos_reg)) <= to_unsigned(9,4); -- set digit value to 9
else -- digit value > 0
digit_next(to_integer(digpos_reg)) <= digit_reg(to_integer(digpos_reg)) -1; -- decrease digit value
end if;
end if;
state_next <= S_FREQ_CONT;
elsif(enc_btn ='1' and btn_old_reg='0') then
if(digpos_reg = to_unsigned(4,3)) then
digpos_next <= to_unsigned(0,3);
else
digpos_next <= digpos_reg + 1;
state_next <= S_FREQ_CONT; -- print frequency
elsif(enc_btn ='1' and btn_old_reg='0') then -- positive edge on push button
if(digpos_reg = to_unsigned(4,3)) then -- digit_pos = 4
digpos_next <= to_unsigned(0,3); -- set digit pos = 0
else -- digit pos < 4
digpos_next <= digpos_reg + 1; -- increase digit pos
end if;
state_next <= S_FREQ_CONT;
state_next <= S_FREQ_CONT; -- print frequency (also updates the cursor position)
end if;
when others => null; -- do nothing, if we are in a different state
end case;

46
dds.vhd
View File

@@ -25,66 +25,72 @@ entity dds is
end dds;
architecture Behavioral of dds is
signal m, idx : unsigned(acc_res -1 downto 0):= (others => '0');
signal idx_phase : unsigned(phase_res-1 downto 0) := (others => '0');
signal amp_rect, amp_saw, amp_tria, amp_sin : unsigned (adc_res-1 downto 0);
signal m, idx : unsigned(acc_res -1 downto 0):= (others => '0'); -- phase jump size and accumulator (see Fundamentals of Direct Digital Synthesis for details about their function)
signal idx_phase : unsigned(phase_res-1 downto 0) := (others => '0'); -- relevant (=leftmost) bits of the phase acccumulator
signal amp_rect, amp_saw, amp_tria, amp_sin : unsigned (adc_res-1 downto 0); -- the current amplitudes of all 4 signal forms
-- Function to genenerate and store the sine wave in the rom.
-- Current code: Only store 1/4 of a sine wave and use symmetries.
-- Uncommented code: Store the entire sine wave (decrease adc_width to 8)
type storage is array (((2**phase_res)/4)-1 downto 0) of unsigned (adc_res-2 downto 0);
--type storage is array (((2**phase_res))-1 downto 0) of unsigned (adc_res-1 downto 0);
function gen_sin_wave return storage is
variable temp : storage;
begin
forLoop: for i in 0 to temp'high loop
forLoop: for i in 0 to temp'high loop -- for each element in the array
temp(i) := to_unsigned(integer(real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI/2.0)/real(temp'high))),adc_res-1);
--temp(i) := to_unsigned(integer(real(2**(adc_res-1) -1) + real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI*2.0)/real(temp'high))),adc_res);
end loop;
return temp;
end function gen_sin_wave;
constant sin_wave : storage := gen_sin_wave;
constant sin_wave : storage := gen_sin_wave; -- rom for sin wave
begin
-- Calculate jump size according to input frequency
-- m = fout*(2^n)/fclk = fout*((2^n)*(2^k)/fclk)/(2^k) with k=ceil(log2(fclk)), n=acc_res
m <= resize( (resize(freq,64)
*
(shift_left(to_unsigned(1,64),acc_res + log2_int(clk_freq)) / clk_freq))
/to_unsigned(2**log2_int(clk_freq),64),acc_res);
-- Amplitude of the square wave
amp_rect <= to_unsigned(0,adc_res) when idx(acc_res-1)='0' else -- 0 for half of the time
to_unsigned((2**adc_res)-1,adc_res); --1 for the rest
amp_rect <= to_unsigned(0,adc_res) when idx(acc_res-1)='0' else
to_unsigned((2**adc_res)-1,adc_res);
-- Amplitude of the sawtooth wave
amp_saw <= idx(acc_res -1 downto acc_res - adc_res); -- Exactly the value of the uppermost bits of the phase acc
amp_saw <= idx(acc_res -1 downto acc_res - adc_res);
-- Amplitude of the triangle wave
amp_tria <= idx(acc_res -2 downto acc_res - adc_res - 1) -- The value of the uppermost bits, except the uppermost one (= double the frequency)
when idx(acc_res-1)='0' else -- during half of the time
((2**adc_res)-1)- (idx(acc_res -2 downto acc_res - adc_res - 1)); -- and the complement, the rest of the time
amp_tria <= idx(acc_res -2 downto acc_res - adc_res) & "0"
when idx(acc_res-1)='0' else
((2**adc_res)-1)- (idx(acc_res -2 downto acc_res - adc_res) & "0");
idx_phase <= idx(acc_res -1 downto acc_res - phase_res); -- take only the uppermost bits for the sine lookup
idx_phase <= idx(acc_res -1 downto acc_res - phase_res);
--amp_sin <= sin_wave(to_integer(idx_phase));
-- Amplitude of the sine wave
-- Code if we had stored the whole sinewave:
-- amp_sin <= sin_wave(to_integer(idx_phase));
-- Current Code (only 1/4 of the sine wave stored)
amp_sin <= to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="00" else
to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(((2**(phase_res-2))-1) - idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="01" else
to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="10" else
to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(((2**(phase_res-2))-1) - idx_phase(phase_res-3 downto 0)));
-- Output the selected amplitue using a multiplexer (00=Rectancle, 01=Sawtooth, 10=Triangle, 11=Sine)
amp <= to_unsigned(0,adc_res) when freq = to_unsigned(0,freq_res) else
amp_rect when form = "00" else
amp_saw when form ="01" else
amp_tria when form = "10" else
amp_sin;
-- Process for the phase accumulator (sequential)
P1: process(clk)
begin
if(rising_edge(clk)) then
idx <= (idx+m);
idx <= (idx+m); -- increment phase accumulator according to jump size. overflow is wanted.
end if;
end process P1;
end Behavioral;

40
rotary.vhd
View File

@@ -23,44 +23,48 @@ end rotary_dec;
architecture Behavioral of rotary_dec is
signal a_old, b_old: std_logic := '0';
signal a_debounced_reg, a_debounced_next, b_debounced_reg, b_debounced_next : std_logic := '0';
signal btn_reg, btn_next: std_logic :='0';
signal counter_a_reg, counter_a_next,
signal a_old, b_old: std_logic := '0'; -- Registers for edge detection on debounced A, B signals
signal a_debounced_reg, a_debounced_next, -- Registers for debouncing A, B signals
b_debounced_reg, b_debounced_next : std_logic := '0';
signal btn_reg, btn_next: std_logic :='0'; -- Registers for debouncing Button Press signal
signal counter_a_reg, counter_a_next, -- Counters to smooth chittering = debounce signals
counter_b_reg, counter_b_next,
counter_btn_reg, counter_btn_next: unsigned(23 downto 0) := (others => '0');
constant count_max: unsigned(23 downto 0) := to_unsigned(500000,24); --10ms
constant count_max: unsigned(23 downto 0) := to_unsigned(500000,24); --Number of cycles during which a signal can't change it's value 50mhz*10ms= 500000 cycles
begin
-- State register process (sequential)
process(clk)
begin
if rising_edge(clk) then
counter_a_reg <= counter_a_next;
counter_b_reg <= counter_b_next;
counter_btn_reg <= counter_btn_next;
a_debounced_reg <= a_debounced_next;
b_debounced_reg <= b_debounced_next;
btn_reg <= btn_next;
a_old <= a_debounced_reg;
b_old <= b_debounced_reg;
btn_reg <= btn_next;
end if;
end process;
btn_deb <= btn_reg;
-- Debounce process (combinational)
process(A,B, a_debounced_reg, b_debounced_reg, counter_a_reg, counter_b_reg, btn_reg, btn, counter_btn_reg)
begin
-- If signal a has changed (edge detection) and enough time passed since the last change
if(A /= a_debounced_reg and counter_a_reg > count_max) then
a_debounced_next <= A;
counter_a_next <= (others => '0');
else
a_debounced_next <= a_debounced_reg;
counter_a_next <= counter_a_reg + 1;
a_debounced_next <= A; -- accept change
counter_a_next <= (others => '0'); -- reset counter
else -- singal has not changed, or not enough time has passed
a_debounced_next <= a_debounced_reg; -- keep old signal value
counter_a_next <= counter_a_reg + 1; -- increase counter by one
end if;
-- Same as above for signal B
if(B /= b_debounced_reg and counter_b_reg > count_max) then
b_debounced_next <= B;
counter_b_next <= (others => '0');
@@ -69,6 +73,7 @@ begin
counter_b_next <= counter_b_reg + 1;
end if;
-- Same as above for button press signal
if(btn /= btn_reg and counter_btn_reg > count_max) then
btn_next <= btn;
counter_btn_next <= (others => '0');
@@ -80,16 +85,19 @@ begin
end process;
-- Dekodierung der Ausgaenge
btn_deb <= btn_reg; --Output debounced btn reg
-- Ouput decode for Rotary Signals (A,B)
process(a_debounced_reg, b_debounced_reg, a_old, b_old)
variable state: std_logic_vector(3 downto 0);
begin
state := a_debounced_reg & b_debounced_reg & a_old & b_old;
state := a_debounced_reg & b_debounced_reg & a_old & b_old; -- Concat to vector
case state is
when "0001" => enc_right <= '0'; enc_ce <= '1';
when "0010" => enc_right <= '1'; enc_ce <= '1';
when others => enc_right <= '0'; enc_ce <= '0';
-- If you want a finer resolution you can simply add more cases here.
-- In our case we only have 1 case for left, and one for right, which works fine.
end case;
end process;

32
spi_driver.vhd
View File

@@ -22,11 +22,12 @@ entity spi_driver is
end spi_driver;
architecture Behavioral of spi_driver is
type states is(S_IDLE, S_WORK);
signal state_reg, state_next: states := S_IDLE;
signal counter_reg, counter_next: unsigned(5 downto 0) := (others => '0');
signal shift_reg, shift_next: unsigned(19 downto 0):= (others => '0');
type states is(S_IDLE, S_WORK); -- FSM: Idle and Work State
signal state_reg, state_next: states := S_IDLE; -- Current and next state register
signal counter_reg, counter_next: unsigned(5 downto 0) := (others => '0'); -- Counter for the bit nr
signal shift_reg, shift_next: unsigned(19 downto 0):= (others => '0'); -- Shift reg for the ouput
begin
-- State register process (combinational)
REGS: process (clk, rst) is
begin -- process start
if rst = '1' then -- asynchronous reset (active high)
@@ -40,32 +41,35 @@ begin
end if;
end process REGS;
mosi <= shift_reg(shift_reg'high) when state_reg=S_WORK else '0';
sck <= '1' when state_reg=S_WORK and counter_reg(0)='1' else '0';
cs <= '1' when state_reg =S_IDLE else '0';
mosi <= shift_reg(shift_reg'high) when state_reg=S_WORK else '0'; -- Mosi: Highest value of shift reg when in Work state, otherwise 0
sck <= '1' when state_reg=S_WORK and counter_reg(0)='1' else '0'; -- Sck: High when in work state and lowest bit 1 (shift will be performed when lowest bit = 0)
cs <= '0' when state_reg =S_WORK else '1'; -- Cs (low active): Low when in state work
-- Next State logic process (combinational)
NSL: process (state_reg, counter_reg, shift_reg, val) is
begin
state_next <= state_reg;
counter_next <= counter_reg;
shift_next <= shift_reg;
case state_reg is -- switch on current state
when S_IDLE => -- currently in idle state
state_next <= S_WORK;
counter_next <= to_unsigned(0,counter_reg'length);
shift_next(19 downto 16) <= "0011"; --Command: Write to and Update (Power Up)
shift_next(15 downto 12) <= "0000"; --Adress: DAC0
-- Initialize shift reg
shift_next(19 downto 16) <= "0011"; -- Command: Write to and Update (Power Up)
shift_next(15 downto 12) <= "0000"; -- Adress: DAC0
shift_next(11 downto 0) <= val; -- DAC Value (12bit)
--shift_next(0 downto -3) <= "XXXX"; -- 4x don't care
when S_WORK => -- currently in work state
if(counter_reg = 24*2 -1) then
state_next <= S_IDLE;
else
counter_next<= counter_reg + 1;
if(counter_reg = 24*2 -1) then -- all bits sent
state_next <= S_IDLE; -- return to idle state
else -- not all bits sent
counter_next<= counter_reg + 1; -- increase bit counter
end if;
if(counter_reg(0)='1') then
if(counter_reg(0)='1') then -- peform shift when lowest bit = 1, shift will be performed when bit = 0
shift_next <= shift_left(shift_reg,1);
end if;
when others => null; -- do nothing, if we are in a different state