module keyboardInput_test(
input ps2_clk,                  // PS/2 clock, ~12kHz
input ps2_in,                   // PS/2 serial data
input G_CLK,                    // global clock, 100kHz
input reset,                    // reset used for clock debounce.
output reg debounced_ps2_clk,   // debounced PS/2 clock.
output reg [0:6] sevenSeg       // 7 segment display.
);

/*
 * [0][LSB]xxxxxx[MSB][P][1] <-- Serial data as it is received.
 *
 * [1][P][MSB]xxxxxx[LSB][0] <-- Data after it is stored in the shift-right register.
 *
 * SCAN_DATA[8:1] signifies the 8-bit scan code for a key that is pressed.
 */

reg [10:0] SCAN_DATA;            /* 8-bit scancode from keyboard in addition
                                    to the start, parity, and stop bit.*/
reg [10:0] temp_data;            // temporary holder of incoming PS/2 data.
reg [3:0]  counter;              // counts negative clock edges.
reg busy;                        // indicates incoming data from the PS/2 module.

/**--Clk debouncing declarations--**/
parameter NDELAY = 524287;
parameter NBITS = 19;
reg [NBITS-1:0] deb_count;
reg xnew;
/**-------------------------------**/

always @(posedge G_CLK) begin    // debounce the PS/2 clock.
    if (reset) begin
         xnew <= ps2_clk;
         debounced_ps2_clk <= ps2_clk;
         deb_count <= 0;
    end
    else if (ps2_clk != xnew) begin
         xnew <= ps2_clk;
         deb_count <= 0;
    end
    else if (deb_count == NDELAY)
         debounced_ps2_clk <= xnew;
    else
         deb_count <= deb_count + 1;
end // done with debounce.

integer k;
always @(negedge debounced_ps2_clk) begin
    for (k=0; k!=10; k=k+1)     // shift-right register for incoming data.
        temp_data[k] <= temp_data[k+1];
    temp_data[10] <= ps2_in;
end

always @(negedge debounced_ps2_clk) begin
    if (counter == 10)          // counts 11 clock edges.
        counter <= 0;
    else
    counter <= counter + 1;
end

always @(posedge G_CLK) begin   // busy goes LOW on the 11th clock edge.
    if (counter == 0 && (ps2_clk))
        busy <= 0;
    else
    busy <= 1;
end

always@ (negedge busy)         // data transfer is considered to be complete
    SCAN_DATA <= temp_data;    // on the falling edge of the "busy" signal.

always@ (SCAN_DATA) begin      // display the numbers pressed on the keyboard.
    case(SCAN_DATA[8:1]) //7'bABCDEFG
        8'h16: sevenSeg <= 7'b0110000; // '1' code
        8'h1E: sevenSeg <= 7'b1101101; // '2'
    8'h26: sevenSeg <= 7'b1111001; // '3'
    8'h25: sevenSeg <= 7'b0110011; // '4'
    8'h2E: sevenSeg <= 7'b1011011; // '5'
    8'h36: sevenSeg <= 7'b1011111; // '6'
    8'h3D: sevenSeg <= 7'b1110000; // '7'
    8'h3E: sevenSeg <= 7'b1111111; // '8'
    8'h46: sevenSeg <= 7'b1111011; // '9'
    8'h45: sevenSeg <= 7'b1111110; // '0'
    8'hF0: sevenSeg <= 7'bx; // "key released" code
    default: sevenSeg <= 7'bx;
    endcase
end
endmodule