用fpga驱动mfrc522

MFRC522是一种高频RFID读写器，可以通过SPI接口与FPGA进行通信。以下是使用Verilog HDL编写的MFRC522驱动程序的示例代码：

module mfrc522 (
    input wire clk,
    input wire reset,
    output wire sda, // SPI数据线
    output wire sck, // SPI时钟线
    input wire cs,   // 片选信号
    input wire irq,  // 中断信号
    input wire rst,  // 复位信号
    input wire mosi, // SPI主机输出从机输入
    output wire miso // SPI主机输入从机输出
);

// 定义MFRC522的命令
localparam CMD_IDLE = 0;
localparam CMD_TRANSCEIVE = 0x0C;
localparam CMD_MFAUTHENT = 0x0E;

reg [7:0] cmd;
reg [7:0] tx_data;
reg [7:0] rx_data;
reg [7:0] rx_len;

// MFRC522的状态机
reg [7:0] state;
localparam STATE_IDLE = 0;
localparam STATE_WAIT_IRQ = 1;
localparam STATE_SEND_CMD = 2;
localparam STATE_SEND_DATA = 3;
localparam STATE_RECV_DATA = 4;

// SPI的状态机
reg [3:0] spi_state;
localparam SPI_IDLE = 0;
localparam SPI_SEND = 1;
localparam SPI_RECV = 2;
localparam SPI_WAIT = 3;

// 初始化MFRC522
initial begin
    cmd <= CMD_IDLE;
    state <= STATE_IDLE;
    spi_state <= SPI_IDLE;
end

// MFRC522的状态转换
always @(posedge clk) begin
    case (state)
        STATE_IDLE: begin
            if (cs == 0) begin
                state <= STATE_WAIT_IRQ;
            end
        end
        STATE_WAIT_IRQ: begin
            if (irq == 0) begin
                cmd <= CMD_TRANSCEIVE;
                tx_data <= 8'h26; // 发送命令：请求天线
                rx_len <= 2;      // 接收数据：ATQA
                state <= STATE_SEND_CMD;
            end
        end
        STATE_SEND_CMD: begin
            if (spi_state == SPI_IDLE) begin
                spi_state <= SPI_SEND;
            end
            if (spi_state == SPI_WAIT) begin
                spi_state <= SPI_RECV;
                state <= STATE_SEND_DATA;
            end
        end
        STATE_SEND_DATA: begin
            if (spi_state == SPI_IDLE) begin
                spi_state <= SPI_SEND;
            end
            if (spi_state == SPI_WAIT) begin
                spi_state <= SPI_RECV;
                state <= STATE_RECV_DATA;
            end
        end
        STATE_RECV_DATA: begin
            if (spi_state == SPI_IDLE) begin
                spi_state <= SPI_SEND;
            end
            if (spi_state == SPI_WAIT) begin
                spi_state <= SPI_RECV;
                state <= STATE_IDLE;
            end
        end
    endcase
end

// SPI的状态转换
always @(posedge clk) begin
    case (spi_state)
        SPI_IDLE: begin
            sck <= 1;
            sda <= 1;
            miso <= 1;
            if (cs == 0) begin
                spi_state <= SPI_SEND;
            end
        end
        SPI_SEND: begin
            sck <= 0;
            if (cmd != CMD_IDLE) begin
                sda <= tx_data[7];
                tx_data <= {tx_data[6:0], 1'b0};
            end
            spi_state <= SPI_RECV;
        end
        SPI_RECV: begin
            sck <= 1;
            rx_data <= {miso, rx_data[7:1]};
            spi_state <= SPI_WAIT;
        end
        SPI_WAIT: begin
            sck <= 0;
            if (rx_len == 0) begin
                cmd <= CMD_IDLE;
                spi_state <= SPI_IDLE;
            end else begin
                rx_len <= rx_len - 1;
                spi_state <= SPI_RECV;
            end
        end
    endcase
end

endmodule

在这个示例中，MFRC522的状态机分为了五个阶段：空闲状态、等待中断信号、发送命令、发送数据、接收数据。SPI的状态机分为了四个阶段：空闲状态、发送数据、接收数据、等待。当FPGA选择MFRC522进行通信时，会进入空闲状态，等待片选信号（cs）变为低电平。然后进入等待中断信号阶段，等待MFRC522请求天线，并接收ATQA信息。发送命令和发送数据阶段是通过SPI接口来完成的，发送命令时将命令放入SPI的数据线，发送数据时将数据放入SPI的数据线，然后通过等待机制等待MFRC522的回应。接收数据阶段则是将数据从SPI接口中读取出来。在每个时钟周期中，状态机会根据当前状态和输入信号来判断是否需要进行状态转换。