module i2c_ctrl(
    input   wire sys_clk    ,
    input   wire sys_rst_n  ,
    
    output  wire scl        ,
    inout   wire sda

);
parameter I2C_CLK_DIV = 5'd24,
          MAX = 10'd1000,
          SLAVE_ID = 7'h73;
//状态机参数定义
parameter IDLE      = 3'd0,
          START     = 3'd1,
          SLAVE_ADDR= 3'd2,
          WAIT      = 3'd3,
          STOP      = 3'd4;
reg [2: 0] state_c;
reg [2: 0] state_n;
////

//i2c时钟计数器
reg [4: 0] cnt_clk;
reg        i2c_clk;
/////

//中间信号定义
reg [9: 0]  cnt_wait    ;//1000us
reg         skip_en_1   ;//跳转信号
reg [2: 0]  step        ;//步骤
reg [1: 0]  cnt_i2c_clk ;//
reg [2: 0]  cnt_bit     ;//bit计数器
reg         i2c_end     ;//i2c结束信号
wire        sda_en      ;
wire        sda_in      ;
reg         i2c_sda     ;
reg         i2c_scl     ;
reg [7: 0]  slave_addr  ;
reg [7: 0]  device_addr ;
reg [7: 0]  wr_data     ;
//三态门
assign sda_en  = 1'b1;//主机控制从机
assign sda_in  = sda;
assign sda     = (sda_en == 1'b1)? i2c_sda : 1'bz;
//i2c驱动时钟设计
always @(posedge sys_clk or negedge sys_rst_n) begin
    if(!sys_rst_n)begin
        cnt_clk <= 5'd0;
    end 
    else if(cnt_clk == I2C_CLK_DIV)begin
        cnt_clk <= 5'd0;
    end 
    else begin
        cnt_clk <= cnt_clk + 1;
    end
end

always @(posedge sys_clk or negedge sys_rst_n) begin
    if(!sys_rst_n)begin
        i2c_clk <= 1'b1;
    end 
    else if(cnt_clk == I2C_CLK_DIV)begin
        i2c_clk <= ~i2c_clk;
    end
    else begin
        i2c_clk <= i2c_clk;
    end 
end
/////////
//状态机，第一段
always @(posedge sys_clk or negedge sys_rst_n) begin
    if(!sys_rst_n)begin
        state_c <= IDLE;
    end 
    else begin
        state_c <= state_n;
    end
end
//状态机第二段
always @(*)begin
    case(state_c)
        IDLE:       if(skip_en_1 == 1'b1)begin
                        state_n = START;
                    end
                    else begin
                        state_n = IDLE;
                    end 
        START:      if(skip_en_1 == 1'b1)begin
                        state_n = SLAVE_ADDR;
                    end 
                    else begin
                        state_n = START;
                    end
        SLAVE_ADDR: if(skip_en_1 == 1'b1)begin
                        state_n = WAIT;
                    end 
                    else begin
                        state_n = SLAVE_ADDR;
                    end 
        WAIT:       if(skip_en_1 == 1'b1)begin
                        state_n = STOP;
                    end 
                    else begin
                        state_n = WAIT;
                    end 
        STOP:       if(skip_en_1 == 1'b1)begin
                        state_n = IDLE;
                    end 
                    else begin
                        state_n = STOP;
                    end 
        default:    begin
                        state_n = IDLE;
                    end
    endcase
end 
//状态机第三段
always @(posedge i2c_clk or negedge sys_rst_n)begin
    if(!sys_rst_n)begin
        cnt_wait    <= 10'd0;
        skip_en_1   <= 1'b0;
        step        <= 3'd0;
        cnt_i2c_clk <= 2'd0;
        cnt_bit     <= 3'd0;
        i2c_end     <= 1'b0;
    end 
    else begin
        case(state_c)
            IDLE:       begin
                            if(cnt_wait == MAX - 1)begin
                                cnt_wait <= 10'd0;
                            end
                            else begin
                                cnt_wait <= cnt_wait + 1;
                            end 
                            if((cnt_wait == MAX - 2'd2) && (step == 3'd0))begin
                                skip_en_1 <= 1'b1;
                            end 
                            else begin
                                skip_en_1 <= 1'b0;
                            end 
                        end 
            START:      begin
                            cnt_i2c_clk <= cnt_i2c_clk + 1'd1;
                            if((cnt_i2c_clk == 2'd2) && (step == 3'd0))begin
                                skip_en_1 <= 1'b1;
                            end 
                            else begin
                                skip_en_1 <= 1'b0;
                            end 
                        end
            SLAVE_ADDR: begin
                            cnt_i2c_clk <= cnt_i2c_clk + 1'd1;
                            if((cnt_i2c_clk == 2'd2) && (cnt_bit == 3'd7) && (step == 3'd0))begin
                                skip_en_1 <= 1'b1;
                            end 
                            else begin
                                skip_en_1 <= 1'b0;
                            end 
                            if((cnt_bit == 3'd7) && (cnt_i2c_clk == 2'd3))begin
                                cnt_bit <= 3'd0;
                            end 
                            else if(cnt_i2c_clk == 2'd3)begin
                                cnt_bit <= cnt_bit + 1'd1;
                            end
                            else begin
                                cnt_bit <= cnt_bit;
                            end 
                        end
            WAIT:       begin
                            if(cnt_wait == MAX - 1'd1)begin
                                cnt_wait = 10'd0;
                            end 
                            else begin
                                cnt_wait <= cnt_wait + 1'd1;
                            end 
                            if((cnt_wait == MAX - 2'd2) && (step == 3'd0))begin
                                skip_en_1 <= 1'b1;
                            end 
                            else begin
                                skip_en_1 <= 1'b0;
                            end
                        end
            STOP:       begin
                            cnt_i2c_clk <= cnt_i2c_clk + 1'd1;
                            if((cnt_i2c_clk == 2'd2) && (step == 3'd0))begin
                                skip_en_1 <= 1'b1;
                            end 
                            else begin
                                skip_en_1 <= 1'b0;
                            end 
                            if(cnt_i2c_clk == 2'd2)begin
                                i2c_end <= 1'b1;
                            end 
                            else begin
                                i2c_end <= 1'b0;
                            end 
                            if(i2c_end == 1'b1)begin
                                step <= step + 1'd1;
                            end 
                            else begin
                                step <= step;                                    
                            end 
                        end 
            default:    begin
                            cnt_wait    <= 10'd0;
                            skip_en_1   <= 1'b0;
                            step        <= step;
                            cnt_i2c_clk <= 2'd0;
                            cnt_bit     <= 3'd0;
                            i2c_end     <= 1'b0;
                        end 
        endcase
    end 
end 
//step
always @(*)begin
    case(step)
        3'd0:   begin
                    slave_addr = {SLAVE_ID, 1'b0};
                    device_addr = 8'h0;
                    wr_data     = 8'h0;
                end
        default:begin
                    slave_addr  = 8'h0;
                    device_addr = 8'h0;
                    wr_data     = 8'h0;
                end
    endcase
end 
//i2c_scl
always @(*)begin
    case(state_c)
        IDLE:       i2c_scl = 1'b1;
        START:      i2c_scl = (cnt_i2c_clk >= 2'd2) ? 1'b1 : 1'b0;
        SLAVE_ADDR: i2c_scl = ((cnt_i2c_clk == 2'd1) || (cnt_i2c_clk == 2'd2)) ? 1'b1 : 1'b0; 
        WAIT:       i2c_scl = 1'b0;
        STOP:       i2c_scl = (cnt_i2c_clk >= 2'd1) ? 1'b1 : 1'b0;    
    endcase
end 
//i2c_sda
always @(*)begin
    case(state_c)
        IDLE:       i2c_sda = 1'b1;
        START:      i2c_sda = (cnt_i2c_clk >= 2'd1) ? 1'b0 : 1'b1;
        SLAVE_ADDR: i2c_sda = slave_addr[7 - cnt_bit];
        WAIT:       i2c_sda = 1'b0;
        STOP:       i2c_sda = (cnt_i2c_clk >= 2'd2) ? 1'b1 : 1'b0;
        default:    i2c_sda = 1'b1;
    endcase
end 
assign scl = i2c_scl;
endmodule