Argus

Optical System

The optical subsystem was highly successful, creating a visible and clear projection of the OLED in the user's view. The text on the OLED was reflected by two mirrors and directed through a convex lens, hitting a beamsplitter that brought half the light into the user's eye. A virtual image was created 256mm in front, overlaid on the rest of the field of view to create the augmented reality effect. The final design used a 25mm diameter convex lens with a 71mm focal point, two 35×15mm first-surface mirrors placed at 45° and parallel to each other, and a 50×30mm 50/50 beamsplitter. Total light path distance was 56mm, producing a virtual image at −265mm with a magnification of 4.73. A key design change — switching from a 32mm to 71mm focal length lens — was required to push the virtual image beyond 250mm, the minimum for a clear human eye focus.

Mechanical System

The enclosure and lid were designed in Fusion 360, with subsystems optimized in Onshape. The enclosure fits the STM32, OLED, IMU, and buttons. Due to soldering difficulty, not all components ended up inside the enclosure during the demo — however, with thinner flexible wires they would fit comfortably, as validated by calipers and CAD assembly. The optical distances were accurately reflected in the CAD, enabling a clear image on the first assembly attempt.

Hardware & Firmware Systems

The hardware in the final product includes an STM32F411CEU6 (STM32 Black Pill) for its small form factor. One of the five SPI peripherals, specifically SPI4, is used to communicate and display information on the DFR0934 OLED, which served as our main output device. The glasses had two main input devices. The first, using the SPI2 peripheral, is the LSM6DS0 IMU that records the step count. The second, using an ADC, is a photoresistor divider that captures the ambient light intensity, which allows the system to automatically adjust OLED brightness. Using the step count, the speed was also approximated (in MPH) and displayed onto the OLED screen. To interface with the smart glasses, four buttons were used to trigger external interrupts via GPIO pins.

To keep the firmware organized, the drivers and code for the SPI peripherals, OLED, ADC, etc. were managed in different files. The main.c file then connects these different files to manage the main GUI. The GUI consisted of five distinct screens that the user could cycle through: the welcome screen, time screen, step-count screen, countdown timer screen, and brightness control screen.

Argus successfully demonstrated a functional pair of bare-metal smart glasses built around the STM32F411CEU. Overall, this project was successful as the most important features were completed and demonstrated. The optics and OLED screen worked well as shown in the demo video — the virtual image was successfully projected and could be comfortably seen ~10 inches in front of the user's eye. The real-time clock and timer also worked accurately. There were challenges primarily due to the compact form factor: to fit all components inside the enclosure, header pins had to be desoldered, which applied excess heat to some GPIO pins and SPI peripherals. One button and the IMU's SPI peripheral were broken as a result. Another button was soldered onto a working GPIO pin, and the OLED's SPI peripheral remained fully functional. Despite these setbacks, the IMU worked during initial testing, and with another STM32 the step counter would have worked. All other features performed well.

From this experience, we learned that building a prototype involves not only just prototyping, but also integrating the final product. Ultimately, this is where we struggled the most to turn design and MVP into functional product. Working with the large Nucleo board was much easier than a STM32 Black Pill with many pins missing functionality. In the future, we would be more deliberate in choosing and assembling parts. Several of the first IMUs chosen simply could not work due to issues between STM32 and those specific I2C peripherals, and even prototyping would have been more deliberate (mostly not soldering in those jumper pins because removing those broke our board). Additionally, we would have bought at least one more board for redundancy. As a next step, we really wanted to pursue more navigational features. We think that Argus could have great application as a tool to notify you in situations where you should keep your attention ahead of yourself, so integration with maps or a compass with more intensive bio-tracking could turn this into a much more functional product.

I. Gbati, Bare-Metal Embedded C Programming: Develop High-Performance Embedded Systems with C for Arm Microcontrollers. Birmingham, UK: Packt Publishing, 2024.

Argus is a pair of augmented reality glasses that utilizes a HUD and sensor suite to collect and display movement information along with live timers that always keep the user up to date with their activities. Using a STM32 MCU and XIAO ESP32S3 processors, we can wirelessly transmit data from the glasses to our pocket. Featuring a transparent OLED for the HUD, a 9-axis IMU for spatial tracking, and capacitive touch sensors, we combine portability with performance. The ESP32s relay data wirelessly from the glasses to the STM32 in the user's pocket which serves as the compute hub.

Argus helps bridge the gap between physical activity and real-time data accessibility without sacrificing situational awareness. While commercial AR glasses often prioritize complex media ecosystems and overlays, Argus focuses on lightweight, purpose-focused architecture that offloads heavy processing to a pocket-based STM32 to minimize weight. The sensors provide a distraction-free, hands-free HUD for users. Instead of having to look at a watch or pull out a phone, users can find relevant telemetry in their line of sight. The emphasis on power efficiency and simplicity makes it perfect for tasks like checking direction of travel while running or biking — where looking down could be unsafe.