When developing embedded application software, balancing performance and power consumption is a constant challenge. Whether you’re working with microcontrollers (MCUs) or other resource-constrained hardware, efficient software design plays a critical role in maximizing battery life whilst ensuring smooth operation.
Here are three practical tips to help embedded engineers get the best of both worlds.
1. Optimize Software Architecture and Code Efficiency
Well-structured software architecture and optimized code can significantly reduce power consumption while maintaining high (or sufficient) performance.
Here’s how:
Use efficient algorithms: Choose data structures and algorithms that minimize processing time and memory accesses. For example, replacing an inefficient O(n^2) sorting algorithm with an O(n log n) alternative can reduce computational load.
Avoid busy-waiting: Implement event-driven programming instead of polling, which keeps the processor active unnecessarily. This allows the use of low-power sleep modes while waiting for events.
Reduce memory operations: Minimize unnecessary and repeated memory allocation and deallocation, as these can cause excessive CPU cycles and power drain.
Leverage hardware accelerators: Many MCUs include dedicated co-processors or DSP units for specific tasks like encryption or signal processing. Using these can offload work from the main processor, reducing power draw.
Quick Tip:
Make use of compiler optimization flags (e.g., -Os for size optimization) and profile your code with tools like EnergyTrace or ARM Cortex-M Power Debugging to find energy-hungry functions.
2. Utilize Power-Aware OS and Middleware Features
Your choice of operating system (OS) and middleware can have a major impact on energy efficiency. Here’s what to look out for:
Use an energy-efficient RTOS or OS: Lightweight real-time operating systems (RTOS) like Zephyr or FreeRTOS offer built-in power management features, such as idle task sleep modes.
Implement low-power operating modes: Many modern MCUs support multiple low-power run and sleep modes, allowing software to scale down power usage dynamically rather than relying solely on CPU frequency adjustments.
Optimize peripheral usage: Configure hardware peripherals to use low-power modes when not in use. For instance, disabling unused timers, reducing ADC sampling frequency, or putting communication modules into low-power states can save energy.
Reduce wake-ups: The fewer times the processor has to wake from a deep sleep state, the better. Batch sensor readings, delay non-critical tasks, and schedule periodic operations efficiently to avoid excessive power consumption.
Utilize clock scaling: Many MCUs allow dynamic adjustment of clock speeds to scale performance based on workload, reducing power consumption during idle or low-demand periods.
Quick Tip:
Use power analysis tools provided by MCU vendors (e.g., ST Power Consumption Calculator, nRF Power Profiler) to fine-tune power management settings and verify real-world power consumption.
3. Profile, Test, and Continuously Optimize
No matter how well-designed your software is, continuous profiling and testing are crucial to maintaining an optimal balance between power and performance.
Here’s what you should focus on:
Monitor energy consumption: Use real-time power measurement tools to track power usage across different software states.
Optimize for real-world conditions: Ensure your application runs efficiently under typical operating scenarios, adjusting configurations based on actual workload rather than worst-case assumptions.
Iterate and improve: Regularly review profiling data and make incremental improvements. Small tweaks—like reducing wake-up frequencies or refining interrupt handling—can add up to significant energy savings over time.
Know What’s Needed: Software doesn’t need to run as fast as possible. It just needs to run fast enough. If it’s possible to slow things down without affecting functionality, you could be using less power.
Quick Tip:
Use power-aware simulators (e.g., Renesas e² studio Power Profiler) to predict the impact of code changes before deploying to hardware, reducing time spent on debugging excessive power consumption.
Final Thoughts
Balancing performance and power consumption in embedded systems is a constant trade-off, but with the right software strategies, you can develop efficient, high-performance applications without sacrificing energy efficiency.
By optimizing software architecture, leveraging power-aware OS features, and continuously profiling power usage, you can maximize the lifetime of battery-powered devices and enhance the overall efficiency of your embedded application.
