写一段基于FPGA的DS18b20的测温代码

### 回答1：
以下是一段基于FPGA的DS18B20温度传感器的代码示例：

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity DS18B20_Temp_Read is
    Port (
        clk : in  STD_LOGIC;
        reset : in  STD_LOGIC;
        DQ : inout  STD_LOGIC;
        temperature : out  STD_LOGIC_VECTOR (11 downto 0)
    );
end DS18B20_Temp_Read;

architecture Behavioral of DS18B20_Temp_Read is
    signal present, data : STD_LOGIC_VECTOR (8 downto 0);
    signal bit_counter : integer range 0 to 80 := 0;
    signal byte_counter : integer range 0 to 9 := 0;

begin
    process(clk, reset)
    begin
        if reset = '1' then
            bit_counter <= 0;
            byte_counter <= 0;
        elsif rising_edge(clk) then
            if bit_counter = 0 then
                DQ <= '0';
                present <= "00000001";
                bit_counter <= 1;
            elsif bit_counter = 1 then
                DQ <= '1';
                bit_counter <= 2;
            elsif bit_counter >= 2 and bit_counter <= 10 then
                present(7 downto 0) <= present(6 downto 0) & DQ;
                bit_counter <= bit_counter + 1;
            elsif bit_counter = 11 then
                DQ <= '0';
                present <= "00000001";
                data(byte_counter * 8 + 7 downto byte_counter * 8) <= present(7);
                bit_counter <= 12;
            elsif bit_counter >= 12 and bit_counter <= 72 then
                data(byte_counter * 8 + 7 downto byte_counter * 8) <= 
                    data(byte_counter * 8 + 6 downto byte_counter * 8) & DQ;
                bit_counter <= bit_counter + 1;
                if bit_counter = 72 then
                    byte_counter <= byte_counter + 1;
                end if;
            elsif bit_counter = 73 then
                DQ <= '1';
                bit_counter <= 74;
            end if;
        end if;
    end process;

    temperature <= data(7 downto 0) & "00";
end Behavioral;

这段代码实现了在FPGA上读取DS18B20温度传感器数据的功能，通过设计一个FSM来控制DQ线的电平并读取数据。

### 回答2：
基于FPGA的DS18B20测温代码如下：

module DS18B20 (
  input wire clk,
  output reg [7:0] temperature
);

reg [2:0] state;
reg [8:0] counter;
reg bit presence_pulse;
reg [1:0] bit_counter;
wire [7:0] temperature_data;

wire read_request = (state == 0);
wire [7:0] reset_command = 8'b00011010;
wire [7:0] read_command = 8'b11100011;
wire [7:0] write_command = 8'b00100001;

always @(posedge clk) begin
  case(state)
    0: 
      begin
        if (counter == 0) begin
          state <= 1;
          presence_pulse <= 0;
        end else begin
          counter <= counter - 1;
        end
      end
    1: 
      begin
        if (counter == 0) begin
          state <= 2;
        end else begin
          counter <= counter - 1;
        end
      end
    2: 
      begin
        if (counter == 0) begin
          state <= 3;
        end else begin
          counter <= counter - 1;
        end
      end
    3: 
      begin
        bit_counter <= 0;
        counter <= 7;
        state <= 4;
      end
    4: 
      begin
        if (counter == 0) begin
          bit_counter <= bit_counter + 1;
          counter <= 7;
          state <= 5;
        end else begin
          counter <= counter - 1;
        end
      end
    5: 
      begin
        if (counter == 0) begin
          counter <= 7;
          state <= 6;
        end else begin
          counter <= counter - 1;
        end
      end
    6: 
      begin
        if (counter == 0) begin
          temperature <= temperature_data[bit_counter];
          if(bit_counter == 7) begin
            state <= 7;
          end else begin
            state <= 4;
          end
        end else begin
          counter <= counter - 1;
        end
      end    
    7:
      begin
        if (counter == 0) begin
          if (presence_pulse == 0) begin
            state <= 8;
          end else begin
            state <= 0;
          end
        end else begin
          counter <= counter - 1;
        end
      end 
    8: 
      state <= 0;
  endcase
end

assign temperature_data = (presence_pulse == 1'b0) ? 0 : (temperature_data << 1) | 1'b1;

always @(read_request) begin
  counter <= 255;
  state <= 0;
  bit_counter <= 0;
  presence_pulse <= 1'b1;
end

endmodule

以上是一个简单的基于FPGA的DS18B20测温代码示例。这段代码使用了Verilog语言来实现，主要通过状态机来控制DS18B20的工作状态和数据接收过程。通过读取温度寄存器的数据，将其转换成二进制形式并通过温度输出端口发送。