Question

我一直试图通过SPI与LTC2426 DAC进行通信，而且我已经失败了。现在我正在寻求帮助。有人能告诉我为什么我的代码不起作用。 CSDAC正常工作，生成SCLK并发送32位，但我仍然可能搞砸了时序。我会非常感谢有人帮我修复代码。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity DAC is
    port
        (
            CLK : in STD_LOGIC;         
            SCLK : out STD_LOGIC;
            MOSI : out STD_LOGIC;
            CSDAC : out STD_LOGIC := '1'        
        );  
end DAC;

architecture Behavioral of DAC is
Signal Counter : Integer range 0 to 32 := 0;
Signal CurrentBit : Integer range 0 to 32 := 0;
Signal DataSent : STD_LOGIC := '1';
Constant Data : STD_LOGIC_VECTOR(31 downto 0) := X"0030FFF0";
Signal Slope : STD_LOGIC := '0';
begin
Prescaler : process(CLK) 
begin
    if rising_edge(CLK) then
        if Counter = 5 then
            Slope <= not(Slope);
            Counter <= 0;
        else
            Counter <= Counter + 1;
        end if;
    end if; 
end process;
SCLK <= SLOPE;
WriteDac : process(CLK) 
begin
    if rising_edge(CLK) then
         if DataSent = '1' then
            if CurrentBit <= 31 then
                CSDAC <= '0';
                MOSI <= Data(CurrentBit);
                CurrentBit <= CurrentBit +1;
            else
                CSDAC <= '1';       
                DataSent <= '0';                
            end if;
         end if;
    end if;
end process;
end Behavioral;

编辑：新代码

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity DAC is
    port
        (
            CLK : in STD_LOGIC;         
            SCLK : out STD_LOGIC;
            MOSI : out STD_LOGIC;
            DEBUG : out STD_LOGIC := '1';
            CSDAC : out STD_LOGIC := '1'        
        );  
end DAC;

architecture Behavioral of DAC is
Signal Counter : Integer range 0 to 6 := 0;
Signal Counter2 : Integer range 0 to 33 := 0;
Signal CurrentBit : Integer range 0 to 33 := 0;
Signal Fixed : STD_LOGIC := '0';
Signal DataSent : STD_LOGIC := '0';
Constant Data : STD_LOGIC_VECTOR(31 downto 0) := X"0FFF0C00";
Signal Slope_last : STD_LOGIC := '0'; 
Signal Slope : STD_LOGIC := '0';
Signal MSS : STD_LOGIC := '0';
begin

WriteDac : process(CLK) 
begin
    if rising_edge(CLK) then
        if Counter = 5 then
            Slope_last <= Slope;
            Slope <= not(Slope);
           if Slope_last = '1' and Slope = '0' then
                if Fixed = '1' then
                    if DataSent = '0' then
                        if CurrentBit <= 31 then
                            CSDAC <= '0';
                            DEBUG <= '0';
                            MOSI <= Data(CurrentBit);
                            CurrentBit <= CurrentBit +1;
                         else
                            MOSI <= '0';
                            CSDAC <= '1';
                            DEBUG <= '1';
                            DataSent <= '1';
                        end if;
                    end if;
                else
                  if Counter2 <= 31 then
                        CSDAC <= '1';
                        DEBUG <= '1';
                        Counter2 <= Counter2 + 1;
                        MSS <= not(MSS);
                        MOSI <= MSS;
                  else  
                        Fixed <= '1';
                        MOSI <= '0';
                  end if;
                end if;
            end if;
        else
            Counter <= Counter + 1;
        end if;
    end if;
end process;
SCLK <= SLOPE;

end Behavioral;

我正在脉冲MOSI，因为当我发送几个比特时，SCLK恢复了。第一次SCLK运行时大约1.4 mhz当我脉冲mosi时它恢复到4.167MHZ注意1.4mhz左右它可以是1.5mhz我不记得太好了。

Answer 1

可能是你的第二个过程应该对SCLK（或斜率）i.s.o敏感。 CLK？您可以查看opencores.org以获取SPI模块的一些示例。即使用Verilog编写，这也不是一个很好的例子。

Answer 2

您必须更新与SCK相关的位计数器（CurrentBit）。 e.g：

...
WriteDac : process(CLK) 
begin
   if rising_edge(CLK) then
      slope_last<=slope;

      if slope_last='1' and slope='0' then -- e.g. falling edge!
          if DataSent = '1' then
 ...

试图在vhdl中实现spi总线

2 个答案: