微處理器 - Lattice LCMXO2-4000HC-4MG132C (STEP-MXO2 V2) - Verilog - UART

參考資訊：
https://ftdichip.com/wp-content/uploads/2024/09/DS_FT232H.pdf
https://wiki.stepfpga.com/uart%E4%B8%B2%E5%8F%A3%E6%A8%A1%E5%9D%97

JTAG腳位


FT232HQ腳位


JTAG腳位需要改成GPIO模式，這樣才可以透過FT232HQ傳輸，不過nextpnr-machxo2目前尚未支援JTAG_PORT設定，因此，需要先透過Lattice Diamond編譯修改JTAG腳位在燒錄到板子


下載Bit Stream時，需要先將JTAGENB接到High(JTAG腳位模式)，下載後，再將JTAGENB接到Low(GPIO模式)，這樣可以就可以透過FT232HQ傳輸資料


main.v

module uart_bus
#( parameter bps_para = 1250 )
(
    input clk_in,
    input rst_in,
    input rs232_rx,
    output rs232_tx
);        
  
wire bps_en_rx;
wire bps_clk_rx;
wire [7:0] rx_data;
  
baud
#( .bps_para (bps_para) )
baud_rx
(    
    .clk_in (clk_in),
    .rst_in (rst_in),
    .bps_en (bps_en_rx),
    .bps_clk (bps_clk_rx)
);
  
uart_rx uart_rx_uut
(
    .clk_in (clk_in),
    .rst_in (rst_in),
    .bps_en (bps_en_rx),
    .bps_clk (bps_clk_rx),
    .rs232_rx (rs232_rx),
    .rx_data (rx_data)
);
  
wire bps_en_tx;
wire bps_clk_tx;
  
baud
#( .bps_para (bps_para))
baud_tx
(
    .clk_in (clk_in),
    .rst_in (rst_in),
    .bps_en (bps_en_tx),
    .bps_clk (bps_clk_tx)
);
  
uart_tx uart_tx_uut
(
    .clk_in (clk_in),
    .rst_in (rst_in),
    .bps_en (bps_en_tx),
    .bps_clk (bps_clk_tx),
    .rx_bps_en (bps_en_rx),
    .tx_data (rx_data),
    .rs232_tx (rs232_tx)
);
  
endmodule
 
module baud
#( parameter bps_para = 1250 )
(
    input clk_in,
    input rst_in,
    input bps_en,
    output reg bps_clk
);    
  
reg [12:0] cnt;
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) 
        cnt <= 1'b0;
    else if ((cnt >= (bps_para - 1)) || (!bps_en))
        cnt <= 1'b0;
    else
        cnt <= cnt + 1'b1;
end
  
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) 
        bps_clk <= 1'b0;
    else if (cnt == (bps_para >> 1))
        bps_clk <= 1'b1;    
    else
        bps_clk <= 1'b0;
end
endmodule
 
module uart_rx
(
    input clk_in,
    input rst_in,
    output reg bps_en,
    input bps_clk,
    input rs232_rx,
    output reg [7:0] rx_data
);    
  
reg rs232_rx0;
reg rs232_rx1;
reg rs232_rx2;    
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) begin
        rs232_rx0 <= 1'b0;
        rs232_rx1 <= 1'b0;
        rs232_rx2 <= 1'b0;
    end else begin
        rs232_rx0 <= rs232_rx;
        rs232_rx1 <= rs232_rx0;
        rs232_rx2 <= rs232_rx1;
    end
end
  
wire neg_rs232_rx = rs232_rx2 & rs232_rx1 & (~rs232_rx0) & (~rs232_rx);    
  
reg [3:0] num;            
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in)
        bps_en <= 1'b0;
    else if (neg_rs232_rx && (!bps_en))
        bps_en <= 1'b1;        
    else if (num == 4'd9)
        bps_en <= 1'b0;            
end
 
reg [7:0] rx_data_r;
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) begin
        num <= 4'd0;
        rx_data <= 8'd0;
        rx_data_r <= 8'd0;
    end else if (bps_en) begin
        if (bps_clk) begin
            num <= (num + 1'b1);
            if (num <= 4'd8)
                rx_data_r[num-1] <= rs232_rx;
        end else if (num == 4'd9) begin
            num <= 4'd0;            
            rx_data <= rx_data_r;    
        end
    end
end
endmodule
 
module uart_tx
(
    input clk_in,
    input rst_in,
    output reg bps_en,
    input bps_clk,
    input rx_bps_en,
    input [7:0] tx_data,
    output reg rs232_tx
);
 
reg rx_bps_en_r;
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in)
        rx_bps_en_r <= 1'b0;
    else
        rx_bps_en_r <= rx_bps_en;
end
 
wire neg_rx_bps_en = rx_bps_en_r & (~rx_bps_en);
 
reg [3:0] num;
reg [9:0] tx_data_r;    
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) begin
        bps_en <= 1'b0;
        tx_data_r <= 8'd0;
    end else if (neg_rx_bps_en) begin   
        bps_en <= 1'b1;
        tx_data_r <= {1'b1, tx_data, 1'b0};    
    end else if (num == 4'd10) begin   
        bps_en <= 1'b0;
    end
end
 
always @ (posedge clk_in or negedge rst_in)
begin
    if (!rst_in) begin
        num <= 1'b0;
        rs232_tx <= 1'b1;
    end else if (bps_en) begin
        if (bps_clk) begin
            num <= num + 1'b1;
            rs232_tx <= tx_data_r[num];
        end else if (num >= 4'd10)
            num <= 4'd0;
    end
end
endmodule

main.lpf

LOCATE COMP "clk_in" SITE "C1";
LOCATE COMP "rst_in" SITE "L14";
LOCATE COMP "rs232_tx" SITE "B4";
LOCATE COMP "rs232_rx" SITE "B6";

連接USB就可以做UART Loopback測試(Baudrate 9600bps)