FPGA基于rs422协议实现与上位机实现串口数据回环代码示例

以下是一个基于 RS422 协议的 FPGA 与上位机实现串口数据回环的代码示例，仅供参考：

FPGA 端代码：

module rs422_loopback(
    input clk,          //时钟信号
    input rst,          //复位信号
    input rx_data,      //串口接收数据
    input rx_dv,        //串口数据有效标志
    output tx_data,     //串口发送数据
    output tx_en        //串口使能信号
);

// 定义状态机状态类型
typedef enum logic [2:0] {
    IDLE,
    WAIT_START,
    WAIT_DATA,
    WAIT_STOP
} state_t;

// 定义状态机的输入和输出信号
state_t state, next_state;
logic rx_data_latch, start_bit, stop_bit;
logic [7:0] data_bits;
logic tx_data_latch;

// 状态机
always_ff @(posedge clk, posedge rst) begin
    if (rst) begin
        state <= IDLE;
        rx_data_latch <= 1'b0;
        start_bit <= 1'b0;
        stop_bit <= 1'b0;
        data_bits <= 8'b0;
        tx_data_latch <= 1'b0;
    end else begin
        state <= next_state;
        rx_data_latch <= rx_data;
        start_bit <= rx_data_latch & ~rx_dv;
        stop_bit <= ~rx_data_latch & rx_dv;
    end
end

// 状态转移逻辑
always_comb begin
    next_state = state;
    tx_en = 1'b0;
    case (state)
        IDLE: begin
            if (start_bit) begin
                next_state = WAIT_DATA;
            end
        end
        WAIT_START: begin
            if (start_bit) begin
                next_state = WAIT_DATA;
            end else begin
                next_state = IDLE;
            end
        end
        WAIT_DATA: begin
            if (rx_dv) begin
                data_bits <= {rx_data_latch, data_bits[7:1]};
                if (stop_bit) begin
                    next_state = WAIT_START;
                    tx_data_latch <= 1'b1;
                end
            end else begin
                next_state = WAIT_STOP;
            end
        end
        WAIT_STOP: begin
            if (stop_bit) begin
                next_state = IDLE;
            end
        end
        default: begin
            next_state = IDLE;
        end
    endcase
end

// 串口发送数据
assign tx_data = tx_data_latch ? data_bits : 8'b11111111;

endmodule

上位机端代码：

import serial

ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)

while True:
    data = ser.read()
    if data:
        ser.write(data)

需要注意的是，以上代码仅为示例代码，具体实现需要根据您的硬件平台和通信需求进行修改和优化。另外，实现串口数据回环需要保证 FPGA 和上位机的串口通信波特率、数据位数、停止位数、校验方式等参数一致，否则将无法正常通信。