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e382092ff9
- strobe samples every 25.6us and change timer to free-run - state resets if strobe=H is held over 200us - correct 1st data (upper nibble of delta-x)
91 lines
1.9 KiB
Verilog
91 lines
1.9 KiB
Verilog
// Outputs input signals from a PS/2 mouse in the MSX mouse protocol
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// Besed on ps2mouse module in MiSTer MSX core
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module ps2mouse
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(
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input clk, // 20MHz
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input reset,
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input strobe,
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output reg [5:0] data,
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input [24:0] ps2_mouse
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);
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wire [11:0] mdx = {{4{ps2_mouse[4]}},ps2_mouse[15:8]};
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wire [11:0] mdy = {{4{ps2_mouse[5]}},ps2_mouse[23:16]};
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always @(posedge clk) begin
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reg [6:0] old_strobe;
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reg [2:0] state = 0;
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reg [8:0] timer = 0; // 20MHz / 512 = 25.6us
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reg [7:0] mx;
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reg [7:0] my;
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reg [11:0] dx;
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reg [11:0] dy;
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reg old_stb;
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old_stb <= ps2_mouse[24];
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if(reset) begin
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dx <= 0;
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dy <= 0;
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data <= 'b110000;
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state <= 0;
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old_strobe <= 7'b0000000;
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timer <= 0;
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end
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else begin
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timer <= timer + 1'b1;
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if(old_stb ^ ps2_mouse[24]) begin
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data[5:4] <= ~ps2_mouse[1:0];
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dx <= dx - mdx;
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dy <= dy + mdy;
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end
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// sampling strobe every 25.6us
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if (&timer) begin
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old_strobe[6:1] <= old_strobe[5:0];
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old_strobe[0] <= strobe;
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if ({old_strobe,strobe} == 8'h0) begin
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// reset: hold L over 200us
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state <= 0;
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end else begin
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case(state)
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0: if(~old_strobe[1] && old_strobe[0] && strobe) begin
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// first strobe: hold H over 50us
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state <= state + 1'd1;
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mx <= dx[8:1];
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my <= dy[8:1];
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dx <= 0;
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dy <= 0;
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data[3:0] <= dx[8:5];
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end
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1: if(old_strobe[0] && ~strobe) begin
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state <= state + 1'd1;
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data[3:0] <= mx[3:0];
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end
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2: if(~old_strobe[0] && strobe) begin
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state <= state + 1'd1;
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data[3:0] <= my[7:4];
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end
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3: if(old_strobe[0] && ~strobe) begin
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state <= state + 1'd1;
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data[3:0] <= my[3:0];
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end
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4: if(~old_strobe[0] && strobe) begin
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state <= 0;
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data[3:0] <= 0;
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end
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endcase
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end
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end
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end
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end
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endmodule
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