Open-Source LDAT (Latency Analyser)

Measuring the delay between a physical mouse click and the resulting pixel change on a screen—often called “click-to-photon” latency—is a critical task for competitive gamers, hardware reviewers, and developers. Open-Source LDAT provides a powerful, DIY solution for this measurement, rivaling commercial tools like NVIDIA’s LDAT through the use of high-performance microcontrollers and custom software optimizations.

At the heart of the project is the Teensy 4.1, chosen for its high-speed I/O capabilities and powerful ARM Cortex-M7 processor. By pairing this with a TEMT6000 ambient light sensor and an SSD1306 OLED display, the system creates a standalone device capable of capturing real-time latency statistics without requiring complex external logging software.

The 8kHz Polling Advantage

One of the most significant features of this firmware is its true 8000 Hz USB polling rate. Standard USB HID devices typically poll at 1000 Hz, which introduces up to 1ms of random jitter into any measurement. This project includes a custom PlatformIO build script that temporarily patches the Teensy core files to enable a 125µs polling interval. This ensures that when the device is used in “Direct Mode” (emulating a mouse), the input delivery is as precise as the highest-end gaming peripherals on the market.

Comprehensive Measurement Modes

The firmware is designed to be versatile, offering several modes to isolate different parts of the latency pipeline:

• Automatic Mode: This mode uses a physical mouse wired into the Teensy. It triggers the mouse’s internal hardware switch, measuring the full pipeline including the mouse’s internal firmware delay, debouncing, the PC’s processing time, and the display’s scanout.
• Direct Mode: The Teensy acts as the USB mouse itself. This removes the physical mouse hardware from the equation, allowing users to isolate the latency contributed specifically by the Operating System, GPU drivers, and the display.
• UE4 Aperture Modes: Optimized for use with specialized benchmarking software like Aperture Grille’s “Black to White,” these modes provide a controlled environment for A/B testing monitor overdrive settings or BIOS configurations.

Understanding the Latency Pipeline

Open-Source LDAT is built on the philosophy that latency is not a single, static number but a sum of several independent cycles. A click must wait for the next USB poll, the game engine must sample that input during its next frame update, and the GPU must render the result in time for the monitor’s next scanout.

Because these cycles (USB, Game Engine, Display) are rarely synchronized, latency naturally varies from click to click. The device’s OLED screen addresses this by displaying not just the last measurement, but a live average, minimum, and maximum. This statistical approach helps users identify the “consistency” of their system, which is often more important for a smooth gaming experience than the raw average speed.

Hardware Diagnostics and Calibration

To ensure accurate results across different environments, the firmware includes a comprehensive hardware diagnostic suite. On boot, the device verifies the connection of the light sensor, display, and host mouse.

Calibration is handled through a dedicated debug menu. Because an OLED monitor has a different “black level” than an LCD or LED panel, users can use the live sensor debug mode to find the perfect light thresholds for their specific screen. This calibration allows the device to work with dedicated software markers (like the NVIDIA Reflex Flash Indicator) or even standard in-game effects like muzzle flashes.

Data Logging and Extensibility

For users performing long-term testing or deep-dive analysis, the project supports SD card data logging. When enabled, every individual measurement is saved to a .csv file on the Teensy 4.1’s onboard microSD slot. This allows for the generation of detailed latency distribution graphs and reports.

With its combination of high-speed hardware, clever software patching, and a simple one-button user interface, Open-Source LDAT stands as a professional-grade tool for anyone looking to quantify and optimize their PC’s responsiveness.