Distance Measurement Using Basys3

Have you ever wondered how everyday devices—like parking sensors, obstacle detection robots, or even automatic taps—measure distance so accurately? I wanted to explore the same idea but do it using an FPGA, where everything happens at the hardware logic level instead of relying on microcontrollers. That’s how this project began.

I built a distance measurement system using the Basys 3 FPGA development board and the popular HC-SR04 ultrasonic sensor. The goal was simple:Trigger the ultrasonic sensor, measure the echo time using FPGA logic, and convert it into a readable distance in real time.

But doing this on an FPGA brought interesting challenges. Unlike Arduino, there are no built-in delay functions or timers—we design the timing hardware ourselves. I implemented:

A pulse generator to send the 10 μs trigger signal

• A pulse generator to send the 10 μs trigger signal

An echo timing counter using the Basys 3’s 100 MHz clock

• An echo timing counter using the Basys 3’s 100 MHz clock

A finite state machine (FSM) to control the workflow

• A finite state machine (FSM) to control the workflow

A distance calculator that converts clock cycles into centimeters

• A distance calculator that converts clock cycles into centimeters

A 7-segment display driver to show the measured distance live

• A 7-segment display driver to show the measured distance live

The result? A fully hardware-level distance measurement system that outputs the object’s distance with impressive speed and accuracy. Watching the 7-segment display update instantly as the object moved closer or farther was the most satisfying moment.

This project helped me understand:

how ultrasonic sensors work at the signal level,

• how ultrasonic sensors work at the signal level,

how to design timing circuits in Verilog/VHDL,

• how to design timing circuits in Verilog/VHDL,

how FSMs efficiently control hardware operations,

• how FSMs efficiently control hardware operations,

and how much control and precision FPGAs offer compared to microcontrollers.

• and how much control and precision FPGAs offer compared to microcontrollers.

In future versions, I plan to add:

filtering to remove noise,

• filtering to remove noise,

a VGA graphical distance display,

• a VGA graphical distance display,

and a UART interface to stream the results to a PC.

• and a UART interface to stream the results to a PC.