📶 第27课：WiFi模块(AT指令)

// AT指令控制器 - 通过UART控制ESP8266
module at_command_ctrl (
    input  wire        clk,
    input  wire        rst,
    // UART接口
    output wire [7:0]  uart_tx_data,
    output wire        uart_tx_start,
    input  wire        uart_tx_busy,
    input  wire [7:0]  uart_rx_data,
    input  wire        uart_rx_valid,
    // 命令接口
    input  wire        cmd_start,     // 启动命令序列
    input  wire [3:0]  cmd_select,    // 选择命令
    output reg         cmd_done,
    output reg         cmd_error,
    // ESP8266状态
    output reg         wifi_connected
);
    // AT命令ROM - 存储命令字符串
    reg [7:0] cmd_rom [0:127];
    reg [6:0] cmd_addr;
    reg [3:0] current_cmd;
    reg       sending;

    initial begin
        // CMD0: "AT
" - 测试
        cmd_rom[0]  = 8'h41; // A
        cmd_rom[1]  = 8'h54; // T
        cmd_rom[2]  = 8'h0D; // 
        cmd_rom[3]  = 8'h0A; // 

        cmd_rom[4]  = 8'h00; // 结束
        // CMD1: "AT+CWMODE=1
" - Station模式
        cmd_rom[16] = 8'h41; cmd_rom[17] = 8'h54; // AT
        cmd_rom[18] = 8'h2B; // +
        cmd_rom[19] = 8'h43; cmd_rom[20] = 8'h57; // CW
        cmd_rom[21] = 8'h4D; cmd_rom[22] = 8'h4F; // MO
        cmd_rom[23] = 8'h44; cmd_rom[24] = 8'h45; // DE
        cmd_rom[25] = 8'h3D; // =
        cmd_rom[26] = 8'h31; // 1
        cmd_rom[27] = 8'h0D; cmd_rom[28] = 8'h0A;
        cmd_rom[29] = 8'h00;
        // CMD2: "AT+CIFSR
" - 查询IP
        cmd_rom[32] = 8'h41; cmd_rom[33] = 8'h54;
        cmd_rom[34] = 8'h2B; cmd_rom[35] = 8'h43;
        cmd_rom[36] = 8'h49; cmd_rom[37] = 8'h46;
        cmd_rom[38] = 8'h53; cmd_rom[39] = 8'h52;
        cmd_rom[40] = 8'h0D; cmd_rom[41] = 8'h0A;
        cmd_rom[42] = 8'h00;
    end

    // 发送状态机
    localparam IDLE=0, SEND_CHAR=1, WAIT_TX=2, NEXT_CHAR=3, WAIT_RESP=4;
    reg [2:0] state;
    reg [19:0] timeout;

    always @(posedge clk) begin
        if (rst) begin
            state <= IDLE; sending <= 0;
            cmd_done <= 0; cmd_error <= 0;
            wifi_connected <= 0;
        end else begin
            cmd_done <= 0;
            case(state)
                IDLE: begin
                    if (cmd_start) begin
                        current_cmd <= cmd_select;
                        cmd_addr <= {cmd_select, 3'b000};
                        state <= SEND_CHAR;
                        sending <= 1;
                        timeout <= 0;
                    end
                end
                SEND_CHAR: begin
                    if (cmd_rom[cmd_addr] == 8'h00) begin
                        state <= WAIT_RESP;
                        sending <= 0;
                        timeout <= 0;
                    end else begin
                        state <= WAIT_TX;
                    end
                end
                WAIT_TX: begin
                    if (!uart_tx_busy) begin
                        state <= NEXT_CHAR;
                    end
                end
                NEXT_CHAR: begin
                    cmd_addr <= cmd_addr + 1;
                    state <= SEND_CHAR;
                end
                WAIT_RESP: begin
                    // 检测"OK"响应(简化)
                    if (uart_rx_valid) begin
                        if (uart_rx_data == 8'h4F) // 'O'
                            wifi_connected <= 1;
                        cmd_done <= 1;
                        state <= IDLE;
                    end else if (timeout >= 5000000) begin
                        cmd_error <= 1;
                        state <= IDLE;
                    end else timeout <= timeout + 1;
                end
            endcase
        end
    end

    assign uart_tx_data = cmd_rom[cmd_addr];
    assign uart_tx_start = (state == SEND_CHAR) &&
                           (cmd_rom[cmd_addr] != 8'h00);
endmodule

module at_command_ctrl_tb;
    logic clk=0, rst=1;
    logic [7:0] uart_tx_data;
    logic uart_tx_start, uart_tx_busy=0;
    logic [7:0] uart_rx_data;
    logic uart_rx_valid=0;
    logic cmd_start, cmd_done, cmd_error;
    logic [3:0] cmd_select;
    logic wifi_connected;

    at_command_ctrl uut(.*);
    always #10 clk = ~clk;

    initial begin
        rst=1; #50; rst=0;
        $display("--- AT指令控制器测试 ---");
        // 发送CMD0: AT测试
        cmd_select=0; cmd_start=1; #20; cmd_start=0;
        // 模拟ESP8266回复"OK"
        wait(uart_tx_start); // 等待发送
        wait(cmd_start == 0);
        #1000;
        uart_rx_data=8'h4F; uart_rx_valid=1; #20; uart_rx_valid=0;
        wait(cmd_done);
        $display("  AT命令完成, connected=%b %s",
                 wifi_connected, wifi_connected?"✓":"FAIL");
        $display("AT指令控制器测试完成 ✓");
        #100; $finish;
    end
endmodule