Interfacing Buzzer with DE0 Nano FPGA

Introduction

A common experiment in Verilog and FPGA programming is implementing a buzzing sound using a buzzer connected to an FPGA board like the DE0 Nano. This project serves as an excellent starting point for beginners to understand key concepts of digital design and interfacing with external devices. The buzzer experiment involves learning the basics of Verilog module structure, designing a simple timing mechanism such as a counter or a state machine, and mapping the output signals to the appropriate I/O pin connected to the buzzer. By completing this experiment, learners gain hands-on experience in controlling an external audio device and gain a foundational understanding of FPGA programming and digital signal processing.

Problem statement

Using a buzzer with FPGA DE0 Nano.

Requirements

1. FPGA DE0 Nano
2. Buzzer
3. Jumper wires

Working

To buzz a buzzer using an FPGA DE0 Nano board, you will first define the I/O pin on the FPGA that will be connected to the buzzer as an output port in the Verilog module. Next, you will create a counter that increments at a specific clock frequency, generating a timing delay for the buzzer sound. When the counter reaches a certain value, the buzzer signal is toggled, producing the buzzing effect. The Verilog code includes an always @(posedge clk) block, which triggers the counter and toggles the buzzer signal whenever a positive clock edge is detected. Finally, the output of the module, the out signal, is assigned to the buzzer signal, allowing it to drive the appropriate I/O pin on the DE0 Nano board and produce the buzzing sound. Once the Verilog code is synthesized and implemented using the DE0 Nano's FPGA design tools, the generated bitstream can be loaded onto the FPGA board. When the bitstream is loaded, the FPGA executes the Verilog code, resulting in the buzzer connected to the specified I/O pin producing the desired buzzing sound according to the defined timing and toggle logic.

Code

Copy and paste the following code into buzzer.v or download it from here:

module buzzer (input  clk,output out);
  reg [31:0] counter;
  reg buzzer_signal;

  initial begin
    buzzer_signal = 1'b0;
    counter = 32'b0;
  end

  always @(posedge clk) begin
    if (counter < 25000000) counter <= counter + 1'b1;
    else begin
      buzzer_signal <= ~buzzer_signal;
      counter <= 32'b0;
    end
  end
  assign out = buzzer_signal;

endmodule

Processing-Pin Planner

Open pin-planner and make the following assignment:

1. clk assigned to PIN_R8.
2. out assigned to PIN_C3.

For Hardware Setup refer DE0 Nano Manual.

Upload the code on board and check the output.

Output

This code implements a basic buzzer functionality on an FPGA board. The buzzer produces a buzzing sound based on the clock signal and the counter value. The counter increments with each clock cycle, determining the timing of the buzzing effect. The buzzer signal is toggled based on the counter reaching a specific value, producing the desired buzzing sound. The output of the module is connected to the appropriate I/O pin on the FPGA board, allowing the buzzer to generate the buzzing sound according to the defined timing and toggle logic.

Conclusion

From this Verilog code for interfacing a buzzer in the DE0 Nano FPGA, we learned several key concepts. Firstly, we saw how to initialize and control signals using Verilog syntax, including the input (clk) and output (out) ports. We observed the use of a clock signal to synchronize the buzzing of the buzzer. The counter was used to determine the timing of the buzzing effect, allowing for a specific frequency. We also witnessed the usage of if-else conditions to handle the toggle action of the buzzer signal. Lastly, we gained insights into assigning the buzzer output value to the designated output port using the assign statement. Overall, this code demonstrated the fundamentals of interfacing a buzzer with an FPGA using Verilog, showcasing how to control the buzzing behavior based on the clock signal.