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Simplified SPI driver. Uses no multiplexer now, but a d-ff.

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T-moe
2016-05-24 11:32:48 +02:00
parent bc78a40708
commit 58120b0a85
1 changed files with 23 additions and 16 deletions
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39
spi_driver.vhd
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@@ -40,42 +40,49 @@ end spi_driver;
architecture Behavioral of spi_driver is architecture Behavioral of spi_driver is
type states is(S_IDLE, S_WORK); type states is(S_IDLE, S_WORK);
signal state_reg, state_next: states := S_IDLE; signal state_reg, state_next: states := S_IDLE;
signal counter, counter_next: unsigned(5 downto 0) := (others => '0'); signal counter_reg, counter_next: unsigned(5 downto 0) := (others => '0');
signal data: unsigned(23 downto 0); signal shift_reg, shift_next: unsigned(19 downto 0):= (others => '0');
begin begin
REGS: process (clk, rst) is REGS: process (clk, rst) is
begin -- process start begin -- process start
if rst = '1' then -- asynchronous reset (active high) if rst = '1' then -- asynchronous reset (active high)
state_reg <= S_IDLE; state_reg <= S_IDLE;
counter <= to_unsigned(0,counter'length); counter_reg <= to_unsigned(0,counter_reg'length);
shift_reg <= to_unsigned(0,shift_reg'length);
elsif rising_edge(clk) then -- rising clock edge elsif rising_edge(clk) then -- rising clock edge
state_reg <= state_next; state_reg <= state_next;
counter <= counter_next; counter_reg <= counter_next;
shift_reg <= shift_next;
end if; end if;
end process REGS; end process REGS;
data(23 downto 20) <= "0011"; --Command: Write to and Update (Power Up) mosi <= shift_reg(shift_reg'high) when state_reg=S_WORK else '0';
data(19 downto 16) <= "0000"; --Adress: DAC0 sck <= '1' when state_reg=S_WORK and counter_reg(0)='1' else '0';
data(15 downto 4) <= val; -- DAC Value (12bit)
data(3 downto 0) <= "0000"; -- 4x don't care
mosi <= data(23 - to_integer(counter srl 1)) when state_reg=S_WORK else '0';
sck <= '1' when state_reg=S_WORK and counter(0)='1' else '0';
cs <= '1' when state_reg =S_IDLE else '0'; cs <= '1' when state_reg =S_IDLE else '0';
NSL: process (state_reg, counter) is NSL: process (state_reg, counter_reg, shift_reg, val) is
begin begin
state_next <= state_reg; state_next <= state_reg;
counter_next <= counter; counter_next <= counter_reg;
shift_next <= shift_reg;
case state_reg is -- switch on current state case state_reg is -- switch on current state
when S_IDLE => -- currently in idle state when S_IDLE => -- currently in idle state
state_next <= S_WORK; state_next <= S_WORK;
counter_next <= to_unsigned(0,counter'length); 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
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 when S_WORK => -- currently in work state
if(counter = 24*2 -1) then if(counter_reg = 24*2 -1) then
state_next <= S_IDLE; state_next <= S_IDLE;
else else
counter_next<= counter + 1; counter_next<= counter_reg + 1;
end if;
if(counter_reg(0)='1') then
shift_next <= shift_left(shift_reg,1);
end if; end if;
when others => null; -- do nothing, if we are in a different state when others => null; -- do nothing, if we are in a different state
end case; end case;