N.C. CHANDU PRASANTH ( Assistant Professor)
`timescale 1ns / 1ps
module traffic_light_tb();
reg clk;
reg reset;
wire red;
wire yellow;
wire green;
traffic_light_controller dut( .clk(clk), .reset(reset), .red(red), .yellow(yellow),
.green(green) );
always #5 clk = ~clk;
initial begin
clk = 0;
reset = 1;
#10 reset = 0;
#100 $finish;
end
always @(posedge clk) begin
$display("RED=%b YELLOW=%b GREEN=%b", red, yellow, green);
end
endmodule.
`timescale 1ns / 1ps
module traffic_light_controller(
input clk, reset,
output reg red, yellow, green );
localparam RED = 3'b001;
localparam YELLOW = 3'b010;
localparam GREEN = 3'b100;
reg [2:0] state;
always @(posedge clk)
begin
if (reset)
state <= RED;
else
case (state)
RED: begin
red <= 1'b1;
yellow <= 1'b0;
green <= 1'b0;
state <= YELLOW;
end
YELLOW: begin
red <= 1'b0;
yellow <= 1'b1;
green <= 1'b0;
state <= GREEN;
end
GREEN: begin
red <= 1'b0;
yellow <= 1'b0;
green <= 1'b1;
state <= RED;
end
endcase
end
endmodule.
`timescale 1ns / 1ps
module vending_machine_tb;
// Inputs
reg clk, reset, cancel;
reg [1:0] coin, sel;
// Outputs
wire PrA, PrB, PrC, change;
// Instantiate the vending machine module
vending_machine uut (
.clk(clk),
.reset(reset),
.cancel(cancel),
.coin(coin),
.sel(sel),
.PrA(PrA),
.PrB(PrB),
.PrC(PrC),
.change(change)
);
// Clock Generation: 10ns period (50MHz clock)
always #5 clk = ~clk;
// Test Procedure
initial begin
// Initialize Inputs
clk = 0;
reset = 1;
cancel = 0;
coin = 2'b00;
sel = 2'b00;
// Hold reset for 20 ns
#20 reset = 0;
// Test Case 1: Insert Rs. 5 and Buy Product A
#10 coin = 2'b01; // Insert Rs. 5
#10 sel = 2'b00; // Select Product A
#10 coin = 2'b00; // Stop inserting coins
#20;
// Test Case 2: Insert Rs. 10 and Buy Product B
#10 coin = 2'b10; // Insert Rs. 10
#10 sel = 2'b01; // Select Product B
#20;
// Test Case 3: Insert Rs. 5 twice (Total Rs. 10) and Buy Product A (Expect Rs. 5 change)
#10 coin = 2'b01; // Insert Rs. 5
#10 coin = 2'b01; // Insert Rs. 5 again (Total Rs. 10)
#10 sel = 2'b00; // Select Product A
#20;
// Test Case 4: Insert Rs. 20 and Buy Product C
#10 coin = 2'b10; // Insert Rs. 10
#10 coin = 2'b10; // Insert Rs. 10 again (Total Rs. 20)
#10 sel = 2'b10; // Select Product C
#20;
// Test Case 5: Insert Rs. 10 and Cancel Transaction
#10 coin = 2'b10; // Insert Rs. 10
#10 cancel = 1; // Press Cancel
#10 cancel = 0; // Release Cancel
#20;
// End Simulation
#50 $finish;
end
// Monitor the signals
initial begin
$monitor("Time = %d, Coin = %b, Sel = %b, Cancel = %b, PrA = %b, PrB = %b, PrC = %b, Change = %b",
$time, coin, sel, cancel, PrA, PrB, PrC, change);
end
endmodule
Design Code:
`timescale 1ns / 1ps
module vending_machine(
input clk, reset, cancel,
input [1:0] coin, sel,
output reg PrA, PrB, PrC, change
);
// State encoding using parameter
parameter S0 = 3'b000, S5 = 3'b001, S10 = 3'b010, S15 = 3'b011, S20 = 3'b100;
reg [2:0] current_state, next_state;
// Sequential logic for state transition
always @(posedge clk or posedge reset) begin
if (reset)
current_state <= S0; // Reset to initial state
else
current_state <= next_state;
end
// Next State Logic (Combinational)
always @(*) begin
case (current_state)
S0: begin
if (coin == 2'b01) next_state = S5;
else if (coin == 2'b10) next_state = S10;
else next_state = S0;
end
S5: begin
if (coin == 2'b01) next_state = S10;
else if (coin == 2'b10) next_state = S15;
else if (cancel) next_state = S0;
else next_state = S5;
end
S10: begin
if (coin == 2'b01) next_state = S15;
else if (coin == 2'b10) next_state = S20;
else if (cancel) next_state = S0;
else next_state = S10;
end
S15: begin
if (coin == 2'b01) next_state = S20;
else if (cancel) next_state = S0;
else next_state = S15;
end
S20: begin
if (cancel) next_state = S0;
else next_state = S20;
end
default: next_state = S0; // Default state
endcase
end
// Output Logic
always @(posedge clk or posedge reset) begin
if (reset) begin
PrA <= 0;
PrB <= 0;
PrC <= 0;
change <= 0;
end
else begin
// Default values (avoid latches)
PrA <= 0;
PrB <= 0;
PrC <= 0;
change <= 0;
case (current_state)
S5: begin
if (sel == 2'b00) begin
PrA <= 1; // Product A (Rs. 5)
change <= 0; // No change needed
end
end
S10: begin
if (sel == 2'b00) begin
PrA <= 1; // Product A (Rs. 5)
change <= 1; // Rs. 5 change
end
else if (sel == 2'b01) begin
PrB <= 1; // Product B (Rs. 10)
change <= 0; // No change needed
end
end
S15: begin
if (sel == 2'b01) begin
PrB <= 1; // Product B (Rs. 10)
change <= 1; // Rs. 5 change
end
end
S20: begin
if (sel == 2'b00) begin
PrA <= 1;
change <= 1; // Rs. 15 change
end
else if (sel == 2'b01) begin
PrB <= 1;
change <= 1; // Rs. 10 change
end
else if (sel == 2'b10) begin
PrC <= 1; // Product C (Rs. 20)
change <= 0; // No change needed
end
end
endcase
// Handle cancellation (return money)
if (cancel)
change <= 1;
end
end
endmodule
#include <ESP8266WiFi.h>
}
#include <ESP8266WiFi.h>
1. Open the Arduino IDE.
2. Go to File Preferences.
3. In the Additional Boards Manager URLs eld, add the following URL for NodeMCU support:
https://arduino.esp8266.com/stable/package_esp8266com_index.json
4. Click OK. 5. Go to Tools Board Boards Manager.
6. Search for esp8266 and install the package
CLIK HERE : IOT LAB HANDOUTS