四线电阻屏verilog驱动程序，基于ADS7843

//本人出入FPGA，可能程序写的不好，请指正。
  1 module touch(
    CLK,RSTn,

    TOUCH_CS,
    TOUCH_IRQ,
    TOUCH_BY,
    TOUCH_CLK,
    TOUCH_MISO,
    TOUCH_MOSI,
    
    test
    );
    input         CLK;
    input         RSTn;
    
    input         TOUCH_BY;
    output         TOUCH_CS;
    //input        TOUCH_IRQ;
    inout        TOUCH_IRQ;
    output         TOUCH_CLK;
    input         TOUCH_MISO;
    output        TOUCH_MOSI;
    
    output [3:0]test;
    reg            TOUCH_CSr;
    reg            TOUCH_CLKr;
    reg            TOUCH_MOSIr;
    
    //check the errer
    reg [7:0]    count_irq;
    reg            irq_flag;
    always @(posedge CLK or negedge RSTn)
    if(!RSTn)begin
        count_irq <= 8'd0;
        irq_flag <= 1'b0;end
    else if(count_irq == 8'd20)
        begin
            count_irq <= 8'd0;
            irq_flag <= 1'b1;
        end
    else 
        count_irq <= count_irq + 1'b1;
        
    assign TOUCH_IRQ = (irq_flag)? 1'bz:1'b0;
    //
    reg [7:0]    count_500ns;
    
    parameter    T500ns = 8'd24;//25*20ns = 500ns = 0.5us
    reg            spi_clk_flag;
    //***************************************************
    `define    spi_clk_open    1'b1
    `define spi_clk_close     1'b0
    //***************************************************
    always @(posedge CLK or negedge RSTn)
    if(!RSTn)
        count_500ns <= 8'd0;
    else if(count_500ns == T500ns || (!spi_clk_flag))
        count_500ns <= 8'd0;
    else if(spi_clk_flag)
        count_500ns <= count_500ns + 1'b1;
        
    reg [7:0]    count_2us;    
    reg            count_2us_flag;
    //*************************************************
    `define    count_2us_open 1'd1
    `define count_2us_close 1'd0
    //*************************************************
    always @(posedge CLK or negedge RSTn)
    if(!RSTn)
        count_2us <= 8'd0;
    else if(count_2us == 8'd99 || (!count_2us_flag))
        count_2us <= 8'd0;
    else if(count_2us_flag)
        count_2us <= count_2us + 1'b1;
    else 
        count_2us <= count_2us;
        
    //**************************************************************
    `define touch_clk_pos    8'd2
    `define touch_clk_neg    T500ns/2
    `define high            1'b1
    `define low             1'b0
    //**************************************************************
    
    parameter touch_cmd_x = 8'b1001_0000;// x_pos
    parameter touch_cmd_y = 8'b1101_0000;// y_pos
    reg [7:0]    state_touch;
    reg [7:0]    count_cmd_bit;
    reg [7:0]    count_dat_bit;
    reg    [11:0]    touch_x1data;
    reg [11:0]    touch_x2data;
    reg [7:0]    count_sample;
    always @(posedge CLK or negedge RSTn)
    if(!RSTn)
        begin
            state_touch <= 8'd0;
            spi_clk_flag <= `spi_clk_close;
            count_cmd_bit <= 8'd0;
            count_sample <= 8'd0;
        end
    else 
        case (state_touch)    
        8'd0:
            if(!TOUCH_IRQ )
                begin
                        state_touch <= 8'd1;
                        count_sample <= 8'd0;
                        TOUCH_CSr <= `low;
                        spi_clk_flag <= `spi_clk_close;
                        count_2us_flag <= `count_2us_close;
                        TOUCH_CLKr <= `low;
                    end
                else
                    begin
                        state_touch <= 8'd0;
                        TOUCH_CSr <= `high;
                        TOUCH_CLKr <= `low;
                    end
            8'd1:
                begin
                    state_touch <= 8'd2;
                    spi_clk_flag <= `spi_clk_open;
                    TOUCH_CSr <= `low;
                    count_cmd_bit <= 8'd9;
                    count_dat_bit <= 8'd16;
                end    
            8'd2://write cmd
                if(count_500ns == `touch_clk_pos)//wait posedge clk
                    begin
                        state_touch <= 8'd3;
                        TOUCH_CLKr <= `low;
                        TOUCH_MOSIr <= touch_cmd_x[count_cmd_bit-2'b10];
                        count_cmd_bit <= count_cmd_bit - 1'b1;
                    end
                else
                    state_touch <= 8'd2;
            8'd3:
                if(count_cmd_bit == 8'd0)
                    begin
                        TOUCH_MOSIr <= 1'd0;
                        TOUCH_CLKr <= `low;
                        if(count_2us == 8'd99)
                            begin 
                                state_touch <= 8'd4;
                                count_2us_flag <= `count_2us_close;
                                count_dat_bit <= 8'd16;
                                spi_clk_flag <= `spi_clk_open;
                                
                            end
                        else 
                            begin 
                                state_touch <= 8'd3;
                                count_2us_flag <= `count_2us_open;
                                spi_clk_flag <= `spi_clk_close;
                            end
                    end
                else if(count_500ns == `touch_clk_neg)
                    begin 
                        state_touch <= 8'd2;
                        TOUCH_CLKr <= `high;
                    end
                else state_touch <= 8'd3;
            8'd4://read data
                if(count_500ns == `touch_clk_neg)//wait negedge clk
                    begin
                        state_touch <= 8'd5;
                        TOUCH_CLKr <= `high;
                        touch_x1data[count_dat_bit-1'b1] <= TOUCH_MISO;
                    end
                else
                    state_touch <= 8'd4;
            8'd5:
                begin
                    state_touch <= 8'd6;
                    count_dat_bit <= count_dat_bit - 1'b1;
                end
            8'd6:
                if(count_dat_bit == 8'd0)
                    begin
                        state_touch <= 8'd7;
                        TOUCH_CLKr <= `low;
                    end
                else if(count_500ns == `touch_clk_pos)
                    begin
                        TOUCH_CLKr <= `low;
                        state_touch <= 8'd4;
                    end
                else 
                    state_touch <= 8'd6;
            
            8'd7:    
                begin
                    state_touch <= 8'd8;
                    spi_clk_flag <= `spi_clk_close;    //close the spi clock
                    TOUCH_CSr <= `high;
                end
            8'd8:
                if(count_2us == 8'd99)
                    begin 
                        state_touch <= 8'd0;
                        count_2us_flag <= `count_2us_close;
                    end
                else 
                    begin 
                        state_touch <= 8'd8;
                        count_2us_flag <= `count_2us_open;
                    end
            
        endcase
    assign TOUCH_CLK  = TOUCH_CLKr;
    assign TOUCH_CS = TOUCH_CSr;
    assign TOUCH_MOSI = TOUCH_MOSIr;    
    assign test = touch_x1data[3:0];//显示采集的第四位数据 
endmodule