Add testbench for top_ultrasonic_led module

- Created a new testbench file `top_ultrasonic_led_tb.vvp` to simulate the `top_ultrasonic_led` module.
- Defined the necessary signals and events for testing the ultrasonic sensor functionality.
- Implemented the main test sequence including triggering the ultrasonic sensor and monitoring the output LEDs based on distance measurements.
- Included timing and state management for accurate simulation of the ultrasonic sensor behavior.

Semaine 1/Capteur_recule/Ultrasonic/ultrasonic_fpga.v

@@ -0,0 +1,71 @@
+module ultrasonic_fpga #(
+    parameter integer CLK_FREQ = 27_000_000  // frequence de clk en Hz
+)(
+    input wire clk,
+    input wire rst,
+    input wire start,           // signal de declenchement 
+    input wire echo,            // retour du capteur
+    output reg trig_out,        // signal envoye au capteur
+    output reg [8:0] distance  // distance mesuree
+);
+
+    reg [2:0] state;
+    reg [8:0] trig_counter;
+    reg [15:0] echo_counter;
+
+    localparam IDLE = 0, TRIG = 1, WAIT_ECHO = 2, MEASURE_ECHO = 3, DONE = 4;
+
+    // Constantes dépendantes de CLK_FREQ
+    localparam integer TRIG_DURATION_CYCLES = CLK_FREQ / 100_000; // 10us
+    localparam integer DIST_DIVISOR = (58 * CLK_FREQ) / 1_000_000; // pour conversion µs -> cm
+
+    always @(posedge clk or posedge rst) begin
+        if (rst) begin
+            state <= IDLE;
+            trig_out <= 0;
+            trig_counter <= 0;
+            echo_counter <= 0;
+            distance <= 0;
+        end else begin
+            case (state)
+                IDLE: begin
+                    if (start) begin
+                        state <= TRIG;
+                    end
+                end
+
+                TRIG: begin
+                    if (trig_counter < TRIG_DURATION_CYCLES) begin
+                        trig_out <= 1;
+                        trig_counter <= trig_counter + 1;
+                    end else begin
+                        trig_out <= 0;
+                        trig_counter <= 0;
+                        state <= WAIT_ECHO;
+                    end
+                end
+
+                WAIT_ECHO: begin
+                    if (echo) begin
+                        echo_counter <= 0;
+                        state <= MEASURE_ECHO;
+                    end
+                end
+
+                MEASURE_ECHO: begin
+                    if (echo) begin
+                        echo_counter <= echo_counter + 1;
+                    end else begin
+                        distance <= (echo_counter*1000) / DIST_DIVISOR;
+                        state <= DONE;
+                    end
+                end
+
+                DONE: begin
+                    state <= IDLE;
+                end
+            endcase
+        end
+    end
+
+endmodule