lin协议 自同步技术verilog代码

以下是一个简单的 Lin 帧发送器的 Verilog 代码，其中包含自同步技术：

module lin_tx(
  input clk,
  input reset,
  input [7:0] data_in,
  output tx_pin
);

  // 定义状态机
  typedef enum logic [3:0] {
    IDLE,
    BREAK,
    SYNC,
    SEND_PID,
    SEND_DATA
  } state_t;
  state_t state, next_state;

  // 定义计数器和计时器
  reg [1:0] count;
  reg [15:0] timer;

  // 定义 Lin 帧结构
  localparam BREAK_FIELD = 0x00;
  localparam SYNC_FIELD = 0x55;
  localparam HEADER_FIELD = 0x80;
  localparam DATA_FIELD = 0x00;

  // 定义 PID 和校验和
  reg [5:0] pid;
  reg [7:0] chksum;

  // 定义发送缓冲区
  reg [9:0] tx_buffer;

  always_ff @(posedge clk) begin
    if (reset) begin
      state <= IDLE;
      count <= 0;
      timer <= 0;
      pid <= 0;
      chksum <= 0;
      tx_buffer <= {BREAK_FIELD, SYNC_FIELD, HEADER_FIELD, pid, DATA_FIELD, DATA_FIELD, DATA_FIELD, DATA_FIELD, DATA_FIELD, DATA_FIELD, chksum};
    end else begin
      state <= next_state;
      count <= count + 1;
      timer <= timer + 1;
      if (count == 2'b11) begin
        count <= 0;
      end
      if (timer == 16'd5000) begin
        timer <= 0;
      end
    end
  end

  always_comb begin
    case (state)
      IDLE: begin
        next_state = BREAK;
        tx_pin = 1'b1;
      end
      BREAK: begin
        next_state = SYNC;
        tx_pin = 1'b0;
      end
      SYNC: begin
        next_state = SEND_PID;
        tx_pin = 1'b1;
      end
      SEND_PID: begin
        next_state = SEND_DATA;
        tx_pin = tx_buffer[9];
        pid = tx_buffer[8:3];
        chksum = chksum + pid;
      end
      SEND_DATA: begin
        next_state = SEND_DATA;
        tx_pin = tx_buffer[count];
        chksum = chksum + tx_buffer[count];
        if (count == 2'b01) begin
          next_state = IDLE;
          chksum = ~chksum;
          tx_buffer[9] = chksum;
        end
      end
      default: begin
        next_state = IDLE;
        tx_pin = 1'b1;
      end
    endcase
  end

endmodule

该代码使用了一个简单的状态机实现 Lin 帧发送器。在每个时钟周期中，通过计数器和计时器控制状态转移和数据发送。在发送数据时，还计算了 PID 和校验和，并将它们添加到发送缓冲区中。最后，将发送缓冲区中的数据逐位发送到 tx_pin 输出端口上，从而实现了 Lin 帧发送。