syncbox16ch_fpga/source/src/spi_reg_reader.v

module spi_reg_reader (
    input clk,   //clock input
    input rst_n, //asynchronous reset input, low active

    //regbus interface
    output reg  [31:0] addr,
    output reg  [31:0] wr_data,
    output reg         wr_en,
    input  wire [31:0] rd_data,      //received serial data 
    //
    input  wire        spi_cs_pin,   //
    input  wire        spi_clk_pin,  //
    input  wire        spi_rx_pin,   //
    output reg         spi_tx_pin
);

  parameter STATE_IDLE = 0;
  parameter STATE_RECEIVE_ADD = 1;
  parameter STATE_READ_REG = 2;
  parameter STATE_TRANSMIT_DATA = 3;
  parameter STATE_RECEIVE_DATA = 4;
  parameter STATE_WRITE_REG = 5;
  parameter ADDRESS_WIDTH_BYTE_NUM = 2;

  zutils_signal_filter #(
      .FILTER_COUNT(5)
  ) cs_filter (
      .clk(clk),
      .rst_n(rst_n),
      .in(spi_cs_pin),
      .out(spi_cs_pin_after_filter)
  );

  zutils_signal_filter #(
      .FILTER_COUNT(2)
  ) clk_filter (
      .clk(clk),
      .rst_n(rst_n),
      .in(spi_clk_pin),
      .out(spi_clk_pin_after_filter)
  );

  zutils_signal_filter #(
      .FILTER_COUNT(2)
  ) spi_rx_filter (
      .clk(clk),
      .rst_n(rst_n),
      .in(spi_rx_pin),
      .out(spi_rx_pin_after_filter)
  );

  //
  // 捕获SPI_CS的下降沿 和 SPI_CLK的上升沿
  // detect:
  //     spi_cs_negedge_tri 
  //     spi_clk_posedge_tri
  //

  zutils_edge_detecter cs_edge_detecter (
      .clk(clk),
      .rst_n(rst_n),
      .in_signal(spi_cs_pin_after_filter),
      .in_signal_falling_edge(spi_cs_negedge_tri)

  );

  zutils_edge_detecter clk_edge_detecter (
      .clk(clk),
      .rst_n(rst_n),
      .in_signal(spi_clk_pin_after_filter),
      .in_signal_rising_edge(spi_clk_posedge_tri),
      .in_signal_falling_edge(spi_clk_negedge_tri)
  );


  /*******************************************************************************
 *                        SPI数据解析，及其部分状态更新                           *
 *******************************************************************************/

  //
  // 
  //
  // cs      : ----______________________________________________
  // clk     : ----------____----____----____----____----____----
  // bitcnt  :           0      1       2      ...      7        0
  // rx      :               .       .       .       .       .
  // tx      :           <======><======><======><======><======>
  // valid   :                                                   .
  // byte_cnt:           0                                       1
  //

  wire [31:0] spi_clk_cnt;
  wire [31:0] spi_byte_cnt;
  wire [ 7:0] bit_cnt;

  zutils_clk_parser clk_parser (
      .clk  (clk),
      .rst_n(rst_n),

      .cs_signal_in (spi_cs_pin_after_filter),
      .clk_signal_in(spi_clk_pin_after_filter),

      .clk_start_signal(spi_clk_start_signal),
      .clk_mid_signal(spi_clk_mid_signal),
      .clk_end_signal(spi_clk_end_signal),
      .clk_cnt(spi_clk_cnt),  //[31:0]
      .byte_cnt(spi_byte_cnt),  //[31:0]
      .clk_bit_cnt(bit_cnt)  //[7:0]
  );


  //
  //  spi_tx_1byte_data 发送
  //
  reg [7:0] spi_tx_1byte_data = 0;
  always @(*) begin
    spi_tx_pin <= spi_tx_1byte_data[bit_cnt];
  end


  //
  //   spi_rx_1byte_data
  //   spi_rx_1byte_data_valid
  //   
  //   当 上升沿触发时,接收1bit数据
  //   当 bit_cnt == 7时 接收完一byte数据
  //
  reg [7:0] spi_rx_1byte_data = 0;
  reg spi_rx_1byte_data_valid = 0;
  always @(posedge clk or negedge rst_n) begin
    if (!rst_n || spi_cs_pin_after_filter) begin
      spi_rx_1byte_data <= 0;
      spi_rx_1byte_data_valid <= 0;
    end else begin
      if (spi_clk_mid_signal) begin
        spi_rx_1byte_data[bit_cnt] <= spi_rx_pin_after_filter;
        if (bit_cnt == 7) spi_rx_1byte_data_valid <= 1;
      end else begin
        spi_rx_1byte_data_valid <= 0;
      end
    end
  end

  /*******************************************************************************
 *                              缓存接收到的数据                               *
 *******************************************************************************/
  reg [7:0] spi_rx_data_cache[0:7];
  genvar i;
  always @(posedge clk or negedge rst_n) begin
    if (!rst_n || spi_cs_pin_after_filter) begin
      spi_rx_data_cache[0] <= 0;
      spi_rx_data_cache[1] <= 0;
      spi_rx_data_cache[2] <= 0;
      spi_rx_data_cache[3] <= 0;
      spi_rx_data_cache[4] <= 0;
      spi_rx_data_cache[5] <= 0;
      spi_rx_data_cache[6] <= 0;
      spi_rx_data_cache[7] <= 0;
    end else begin
      // 选中状态
      if (spi_rx_1byte_data_valid && spi_byte_cnt <= 7) begin
        spi_rx_data_cache[spi_byte_cnt] <= spi_rx_1byte_data;
      end
    end
  end



  /*******************************************************************************
 *                 自动设置SPI需要发送的数据 spi_tx_1byte_data                 *
 *******************************************************************************/
  always @(*) begin
    case (spi_byte_cnt)
      ADDRESS_WIDTH_BYTE_NUM + 0: spi_tx_1byte_data <= rd_data[7:0];
      ADDRESS_WIDTH_BYTE_NUM + 1: spi_tx_1byte_data <= rd_data[15:8];
      ADDRESS_WIDTH_BYTE_NUM + 2: spi_tx_1byte_data <= rd_data[23:16];
      ADDRESS_WIDTH_BYTE_NUM + 3: spi_tx_1byte_data <= rd_data[31:24];
      default: spi_tx_1byte_data <= 0;
    endcase
  end

  /*******************************************************************************
     *                              自动设置addr数值                               *
     *******************************************************************************/
  always @(*) begin
    case (ADDRESS_WIDTH_BYTE_NUM)
      0: begin
        addr[7:0]   <= 0;
        addr[15:8]  <= 0;
        addr[23:16] <= 0;
        addr[31:24] <= 0;
      end
      1: begin
        addr[7:0]   <= {1'b0, spi_rx_data_cache[0][6:0]};
        addr[15:8]  <= 0;
        addr[23:16] <= 0;
        addr[31:24] <= 0;
      end
      2: begin
        addr[7:0]   <= spi_rx_data_cache[0][7:0];
        addr[15:8]  <= {1'b0, spi_rx_data_cache[1][6:0]};
        addr[23:16] <= 0;
        addr[31:24] <= 0;
      end
      3: begin
        addr[7:0]   <= spi_rx_data_cache[0][7:0];
        addr[15:8]  <= spi_rx_data_cache[1][7:0];
        addr[23:16] <= {1'b0, spi_rx_data_cache[2][6:0]};
        addr[31:24] <= 0;
      end
      4: begin
        addr[7:0]   <= spi_rx_data_cache[0][7:0];
        addr[15:8]  <= spi_rx_data_cache[1][7:0];
        addr[23:16] <= spi_rx_data_cache[2][7:0];
        addr[31:24] <= {1'b0, spi_rx_data_cache[3][6:0]};
      end
    endcase
  end

  /*******************************************************************************
   *                                   wr_data                                   *
   *******************************************************************************/
  always @(*) begin
    wr_data[7:0]   <= spi_rx_data_cache[ADDRESS_WIDTH_BYTE_NUM];
    wr_data[15:8]  <= spi_rx_data_cache[ADDRESS_WIDTH_BYTE_NUM+1];
    wr_data[23:16] <= spi_rx_data_cache[ADDRESS_WIDTH_BYTE_NUM+2];
    wr_data[31:24] <= spi_rx_data_cache[ADDRESS_WIDTH_BYTE_NUM+3];
  end

  /*******************************************************************************
   *                                    wr_en                                    *
   *******************************************************************************/
  reg has_trigger_wr_en = 0;
  always @(posedge clk or negedge rst_n) begin
    if (!rst_n || spi_cs_pin_after_filter) begin
      wr_en <= 0;
      has_trigger_wr_en <= 0;
    end else begin
      if (!has_trigger_wr_en &&  //
          spi_byte_cnt == ADDRESS_WIDTH_BYTE_NUM + 4 &&  //
          spi_rx_data_cache[ADDRESS_WIDTH_BYTE_NUM-1][7]) begin
        wr_en <= 1;
        has_trigger_wr_en <= 1;
      end else begin
        wr_en <= 0;
      end
    end
  end



endmodule