From the third last line add another case statement, so that the stepper rotates in the other direction.

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reg [3:0] secondsCounter; reg [31:0] clockCount1; reg [3:0] Q; reg led;

/////////// 4 bit/LED counter /////////////// localparam SECOND_DIVIDER = 16000000; // - suit the BX clock always @ (posedge clk) begin if(secondsCounter == 4'b1111 || rst == 0) // resets after 15 iterations secondsCounter <= 1'b0; clockCount1 = clockCount1 + 1'b1; // inc to slow down motor if(clockCount1 == SECOND_DIVIDER) begin clockCount1 <= 1'b0; secondsCounter <= secondsCounter + 1'b1; // inc to 15, the increase delay time per stage end end

/////////// Stepper Motor - half step method (using 28BYJ-48) /////////////// parameter STEPPER_DIVIDER = 16000; // every 1ms, minimum dewel time between changes - suits the 28BYJ -48

reg [31:0] clockCount3; reg [4:0] step; // 16 positions for half steps always @ (posedge clk) begin if(clockCount3 >= STEPPER_DIVIDER * (secondsCounter + 1)) //inc the delay between output update by the Case begin step <= step + 1'b1; clockCount3 <= 1'b0; end else clockCount3 <= clockCount3 + 1'b1; end always @ (step) // use blocking begin led = step[0]; // used to sample sequnce updating Hz if (dir) begin // *** case(step) // move motor clockwise, by passing these sequence's when step changes [0 . . 15] 0: Q = 4'b1000; 1: Q = 4'b1100; 2: Q = 4'b0100; 3: Q = 4'b0110; 4: Q = 4'b0010; 5: Q = 4'b0011; 6: Q = 4'b0001; 7: Q = 4'b1001; 8: Q = 4'b1000; 9: Q = 4'b1100; 10: Q = 4'b0100; 11: Q = 4'b0110; 12: Q = 4'b0010; 13: Q = 4'b0011; 14: Q = 4'b0001; 15: Q = 4'b1001; endcase end else // *** begin // Add another case statement, so that the stepper rotates in the other direction end // *** end