Creating Energy-Efficient Wearable Interfaces Using Sparklet
Overview
In the fast-growing wearables market, user interfaces must be sleek, intuitive, and power-efficient. A leading health-tech company approached Embien Technologies to develop the user interface for their next-generation fitness-focused smartwatch powered by an STM32 microcontroller. The key challenge was to deliver rich, animated visuals on a compact screen, all while preserving battery life for multiple days of operation.
Challenge
The chosen platform, based on the STM32L4 series, offered low-power operation and a basic 2D graphics engine but came with tight constraints in terms of RAM, Flash, and processing speed. Off-the-shelf graphics libraries were either too resource-intensive or lacked the flexibility needed for wearable design. The project demanded a lightweight, customizable solution optimized for both performance and energy efficiency.
Solution
Embien’s Sparklet graphics engine proved to be the perfect fit. Specifically engineered for MCU environments like STM32, Sparklet uses fixed-point rendering, zero-floating-point arithmetic, and an ultra-compact rendering pipeline. Its smart update mechanism—based on dirty rectangle tracking and selective rendering—reduced display refresh overheads, minimizing processor activity and extending battery life significantly.
The UI was designed using Flint, Embien’s intuitive visual design tool, which enabled quick creation of interface screens featuring activity dashboards, health stats, notifications, and gesture support. These designs were directly exported into Sparklet’s runtime-ready format, streamlining integration on the STM32 firmware. Despite the limited system resources, Sparklet enabled smooth transitions, live updates of sensor values, and low-latency interactions.
Performance evaluation on the final hardware demonstrated exceptional results. The user interface consistently achieved frame rates between 25 to 30 FPS during active usage, ensuring a smooth and responsive user experience. In low-power standby modes, the system’s current consumption remained below 10 µA, attributed to Sparklet’s optimized rendering and minimal CPU wake activity. Under typical usage scenarios, the smartwatch delivered over 10 days of battery life on a single charge—significantly exceeding the original design expectations.
Conclusion
By harnessing Sparklet on STM32, Embien delivered a power-optimized, visually engaging UI ideal for wearable applications. The solution is now commercially available across multiple markets and is being adapted for additional wearable models, reaffirming Sparklet’s ability to bring advanced graphics to even the most constrained embedded systems.