`timescale 1ps/1ps

/* verilator lint_off DECLFILENAME */
/* verilator lint_off MULTITOP */
/* verilator lint_off STMTDLY */
/* verilator lint_off INFINITELOOP */
/* verilator lint_off INITIALDLY */

module i2c_io_output_tb;
    logic clock = 1'b0;
    logic reset = 1'b1;

    /* Master clock 100MHz (10ns period) */
    always #(10ns/2) clock = ~clock;

    parameter SCL_PERIOD = 364793; // ~300ns
    logic scl_async;
    logic sda_async;

    event scl_low_ev;
    event scl_high_ev;

    initial begin
        scl_async = 1'b1;

        forever begin
            #(SCL_PERIOD/4) scl_async = 1'b1;
            #(SCL_PERIOD/4) -> scl_high_ev;
            #(SCL_PERIOD/4) scl_async = 1'b0;
            #(SCL_PERIOD/4) -> scl_low_ev;
        end
    end

    parameter IO_BYTES_COUNT = 2;
    parameter [6:0] I2C_ADDRESS = 7'h5a;
    localparam DATA_WIDTH = IO_BYTES_COUNT * 8;

    logic i_scl;
    logic i_sdi;
    logic o_sdo;
    logic [DATA_WIDTH-1:0] o_data;

    i2c_io_output #(.I2C_ADDR(I2C_ADDRESS),
                    .IO_BYTES_COUNT(IO_BYTES_COUNT))
    DUT (.*);

    logic [1:0] scl_sync;
    logic [1:0] sda_sync;

    always_ff @(posedge clock)
      if (reset) begin
          scl_sync <= '1;
          sda_sync <= '1;
      end
      else begin
          scl_sync <= {scl_sync[0], scl_async};
          sda_sync <= {sda_sync[0], sda_async};
      end

    assign i_scl = scl_sync[1];
    assign i_sdi = sda_sync[1];

    task send_start;
        wait(scl_async == 1'b0);
        sda_async = 1'b1;
        @(scl_high_ev);
        sda_async = 1'b0;
    endtask

    task send_stop;
        wait(scl_async == 1'b0);
        sda_async = 1'b0;
        @(scl_high_ev);
        sda_async = 1'b1;
    endtask

    task send_byte(logic [7:0] b);
        for (int n = 7; n >= 0; n -= 1) begin
            @(scl_low_ev);
            sda_async = b[n];
        end

        @(scl_low_ev);
        wait(scl_async == 1'b1);
    endtask

    initial begin
        reset = 1'b1;
        repeat(2) @(posedge clock) #1;
        reset = 1'b0;
        repeat(2) @(posedge clock) #1;

        send_start;
        send_byte(8'hb4);
        send_byte(8'ha5);
        send_byte(8'h38);
        send_byte(8'h42);
        send_stop;

        repeat(1000) @(posedge clock) #1;
        $finish;
    end

`ifdef DUMP
    initial begin
        $dumpfile("i2c_io_output_tb.fst");
        $dumpvars(0, i2c_io_output_tb);
    end
`endif

endmodule // i2c_io_output_tb