用verilog写一个iic通讯协议

好的，以下是基于Verilog的I2C通讯协议实现示例：

module i2c_master(
  input clk,
  input rstn,
  input sda_i,
  output reg sda_o,
  output reg scl_o
);

// 定义I2C状态机
typedef enum logic [2:0] {
  IDLE = 3'b000,
  START = 3'b001,
  ADDR = 3'b010,
  DATA = 3'b011,
  STOP = 3'b100
} i2c_state_t;

// 定义I2C数据包结构体
typedef struct packed {
  logic [6:0] addr; // I2C设备地址
  logic [7:0] data; // 数据
  logic [7:0] ack;  // ACK标志
} i2c_packet_t;

// 定义I2C状态和数据包
i2c_state_t state;
i2c_packet_t packet;

// 定义定时器计数器和比较值
reg [15:0] counter;
localparam [15:0] clock_cycles = 50; // 时钟周期计数值

// 初始化状态机
always_comb begin
  case(state)
    IDLE: begin // 空闲状态
      sda_o <= 1;
      scl_o <= 1;
      if(packet.addr != 0) begin
        state <= START;
        counter <= 0;
      end
    end
    START: begin // 发送START信号
      sda_o <= 0;
      scl_o <= 0;
      if(counter == clock_cycles) begin
        state <= ADDR;
        counter <= 0;
      end else begin
        counter <= counter + 1;
      end
    end
    ADDR: begin // 发送设备地址
      sda_o <= packet.addr[6];
      scl_o <= 1;
      if(counter == clock_cycles) begin
        state <= DATA;
        counter <= 0;
      end else begin
        counter <= counter + 1;
      end
    end
    DATA: begin // 发送数据
      sda_o <= packet.data[7];
      scl_o <= 1;
      if(counter == clock_cycles) begin
        packet.data <= {packet.data[6:0], sda_i};
        counter <= 0;
        if(packet.ack == 1) begin
          state <= STOP;
        end
      end else begin
        counter <= counter + 1;
      end
    end
    STOP: begin // 发送STOP信号
      sda_o <= 0;
      scl_o <= 1;
      if(counter == clock_cycles) begin
        sda_o <= 1;
        state <= IDLE;
        packet.addr <= 0;
        packet.data <= 0;
        packet.ack <= 0;
        counter <= 0;
      end else begin
        counter <= counter + 1;
      end
    end
  endcase
end

// 监听SDA线
always @(posedge clk) begin
  if(!rstn) begin
    packet.addr <= 0;
    packet.data <= 0;
    packet.ack <= 0;
  end else begin
    case(state)
      ADDR: begin
        packet.addr <= {packet.addr[5:0], sda_i};
      end
      DATA: begin
        packet.data <= {packet.data[6:0], sda_i};
        if(counter == clock_cycles) begin
          packet.ack <= ~sda_i;
        end
      end
    endcase
  end
end

endmodule

这是一个简单的I2C主设备实现，包含一个状态机和一个数据包结构体。状态机包括五个状态：空闲、发送START信号、发送设备地址、发送数据和发送STOP信号。I2C数据包结构体包括设备地址、数据和ACK标志。在每个时钟周期内，根据状态机的当前状态和计数器的值，输出对应的SDA和SCL信号，同时更新数据包内容。在监听SDA线的过程中，根据当前状态和SDA线的值，更新数据包内容和ACK标志。