Embedded Systems and Low-Power Design

An embedded system refers to a specialized computer system designed to perform dedicated functions within a larger mechanical or electrical system. It typically consists of a combination of hardware and software components tailored to perform specific tasks or functions. Embedded systems play a crucial role in mobile robotics, UAV construction and edge AI. Such systems are characterized by their real-time operation, reliability and efficiency in executing predetermined functions, often with limited resources such as processing power, memory and energy. In remote areas, for example, everything is run off batteries or generators. Consequently, many embedded systems are engineered to incorporate various techniques to extend battery life. The others simply need to consume less energy based on other factors. As a result, there’s an increasing demand for designs that minimize energy usage while maintaining high performance. In this article we are going to elaborate on the strategies for achieving low-power designs and highlight their significance in embedded systems.

The Need for Low-Power Design

Low-power design involves strategies and approaches aimed at decreasing the energy usage of electronic devices and refers especially to the underlying embedded systems upon which such devices operate. Examples of such devices are battery-powered devices, processors, IoT wireless sensor networks and many more. Through the application of low-power design methods, engineers can create high-quality and reliable equipment which consume considerably less energy without any indication of performance degradation. The need for low-power devices arises from several factors:

• Power sources are often limited and the disruption in the energy supply can result in adversities. This is particularly true for battery-powered devices in military situations where power outages can cost lives. That’s why defense is always looking for lower power consumption in airborne and ground vehicle applications.
• Portability of everyday devices (notebooks, smartphones, etc.) which will have prolonged battery life is one of the concerns of device manufacturing companies. In today’s world, it is a common tendency for customers to have a preference for devices with extended battery life.
• Low-power design will certainly have a huge positive impact on the environment as a large amount of electricity is wasted through devices connected to the grid. The decrease in the electricity consumption of such devices will result in less costs and will cause less damage to the environment.
• In embedded systems, high power consumption can result in a significant amount of heat generation damaging the system components. The reduction of generated heat is one of the concerns for military equipment production. As a fact, the overall decrease in power consumption will considerably reduce the generated heat. Consequently, initially employing low-power design techniques will protect the system from unexpected side effects due to thermal issues.
• Less heat generation can lead to improved performance and reliability of the embedded system. Overheating can cause performance degradation or even hardware failures, so by keeping temperatures within acceptable limits, low-power designs contribute to overall reliability and durability of the system.

Key Principles of Low-Power Design

To grasp the fundamental principles of low-power design, it’s imperative to dive into power consumption basics, sleep modes, clock gating techniques and voltage scaling strategies. This exploration will shed light on how each aspect contributes to the creation of energy-efficient embedded systems.

Power Consumption Basics

Power consumption indicates how much electrical energy a device or a system uses to perform its functions or operations. There are two primary sources of power consumption in electronic devices – static and dynamic. Devices consume static power when idle and dynamic power during active use. Reducing both static and dynamic power consumption is essential for creating low-power designs achieved through the means of efficient components and optimized circuits. Understanding consumption allows informed decisions on resource allocation and environmental impact mitigation. Embracing energy-efficient practices drives towards sustainability while ensuring reliable access to necessities.

Power Management and Sleep Modes

Implementing sleep modes and power states can significantly reduce power consumption in embedded systems. Sleep modes enable devices to enter low-power states when not performing tasks, therefore conserving energy. Power states define consumption levels based on system activity and performance needs. Selecting appropriate modes ensures optimal power usage and performance while maintaining efficiency.

All sleep modes are accessible from active mode, where the CPU executes application code. Upon entering sleep mode, program execution halts, and the device relies on interrupts or a reset for waking up. The application code determines the timing and choice of sleep mode. Enabled interrupts from peripherals and reset sources can return the CPU from sleep to active mode. Furthermore, power reduction registers offer means to halt individual peripheral clocks via software control. This action freezes the peripheral’s current state, eliminating its power consumption. Consequently, power usage is minimized in both active mode and idle sleep modes, facilitating more nuanced power management than sleep modes alone.

Here are several examples of low-power modes:

Sleep Mode: In this mode, the device reduces its power consumption by powering down non-essential components while retaining data in memory. The CPU typically enters a low-power state, halting its operation until an external event, such as a button press or an interrupt, wakes it up.

Deep Sleep Mode: This mode is an even lower power state compared to sleep mode. In deep sleep, the device shuts down most of its non-essential functions, including reducing power to the CPU and peripherals. This mode is commonly used in battery-powered devices to prolong battery life during extended periods of inactivity.

Standby Mode: This mode is similar to sleep mode but may involve a slightly higher level of power consumption. In this mode, the device reduces power to most components, but some essential functions remain active to enable quick recovery. It’s commonly used in devices like TVs and remote controls, where rapid responsiveness is necessary.

Clock Gating for Dynamic Power Reduction

Clock gating is a technique aimed at reducing dynamic power consumption by selectively switching off unnecessary clock signals to registers using control signals, all while ensuring functional correctness. By turning off the clock to idle parts of a device, it conserves power, directing it only to active components and minimizing waste. Implementing clock gating in embedded systems can substantially reduce power usage, particularly in devices with numerous components or intricate functionalities.

Typically, the assignment to a register might be conditional, as depicted above. When EN is 0, the clocks to the registers can be stopped otherwise the registers will switch states on each clock cycle, which dissipates power.

Voltage Scaling Strategies

Voltage scaling strategies in low-power design involve adjusting the core supply voltage to align with the system’s performance needs. Decreasing voltage decreases power consumption, but it can impact performance, necessitating a careful balance between the two. Techniques like adaptive voltage scaling and dynamic voltage scaling are commonly used in embedded systems to find this balance, often coupled with frequency scaling to maintain acceptable performance levels while reducing power consumption. Dynamic Voltage and Frequency Scaling (DVFS) is a power management technique that adjusts the voltage and frequency of the device’s CPU dynamically based on workload demands. During periods of low activity, the CPU voltage and frequency are decreased to save power, while they are increased during high-demand tasks to maintain performance. These strategies are particularly crucial in portable devices where battery life is a primary concern.

Design Techniques for Low-Power Embedded Systems

When thinking about the low-power embedded systems, there is no single rule that applies to every type of requirement. Rather it is a combination of a system design, circuit design and firmware design all combined and working together to deliver the best performance per watt. Embedded engineers construct embedded systems using various low-power techniques, allowing for adaptable control over device’s energy usage based on its activities and operating patterns. 

Hardware Techniques for Low-Power Design

In the realm of low-power embedded system design, the selection of hardware components plays a pivotal role. Optimal choices can significantly influence the system’s overall power consumption. This section will delve into various hardware techniques, such as component selection for low-power embedded systems, employing energy-efficient microcontrollers and processors, and integrating sensors designed for minimal energy consumption.

Energy-efficient component selection: Picking the right components is crucial for any electronic system, affecting design, layout, and power usage. When it comes to low-power designs, choosing components wisely is even more critical. To reduce power consumption in embedded systems, we need to focus on factors like operating voltage, idle/standby current, and overall efficiency of the components. Opting for parts with lower consumption can significantly cut down on energy usage in the system.

Energy-efficient microcontroller and processor selection: Embedded systems rely heavily on microcontrollers and processors, and their power efficiency is crucial in determining overall power usage. When choosing a microcontroller or a processor, prioritize components with low operating voltages, effective sleep modes, and power-saving capabilities like clock gating and voltage scaling. Incorporating these features ensures decreased power consumption without compromising performance, making them ideal choices for energy-conscious designs.

One example of a low-power AI accelerator is Hailo-15 that can process multiple video streams in real time on a single device with robust onboard network connectivity. It offers very high AI performance of 26 TOPS and very low power consumption of 2.5W which makes it perfect for AI computing and for mission-critical applications with power consumption reduced by approximately 70% compared to GPU based solutions. Another example is Intel’s hybrid CPU architecture, which combines “P cores” for high-intensity computational tasks and “E cores” for handling less-intensive tasks while maximizing energy-efficiency, addressing the requirements of modern computing.

Energy-efficient process node selection: When talking about semiconductor ICs, selecting newer devices with 5nm technology node vs 10nm reduces power by 40%, 3nm improves 45% over 5nm, 14nm reduces power by 50% over 28nm etc. Power efficiency can be dramatically improved when using IC built on top of latest technology node.

Energy-efficient FPGA design: Field-Programmable Gate Array (FPGA) devices offer the advantage of flexibility and customization in hardware design. In certain applications, this flexibility can lead to power reduction by combining multiple functions into a single FPGA device rather than using discrete components.

Energy-efficient sensor selection: Sensors play a crucial role in embedded systems, gathering data from the surroundings or user interactions. Opting for sensors with minimal power demands that can transition into low-power modes when inactive is a key. Furthermore, explore sensors equipped with built-in power management functionalities like automatic sleep modes and adjustable sample rates to enhance energy efficiency even further. By selecting sensors with these capabilities, overall power consumption in the system can be significantly reduced, ensuring efficient operation.

Software Techniques for Low-Power Design

It is generally more effective to begin monitoring the energy consumption as early as possible to access the potential risks of high energy consumption points during the implementation process. When the software is already implemented and integrated, it is usually more difficult and expensive to eliminate such issues. On the other hand, energy consumption levels are directly proportional to computational complexities and improving one will result in indirect improvement of the other. Therefore, it is a good idea to introduce several software development techniques to achieve low-power in embedded systems.

Code optimization: Optimize algorithms to reduce the overall CPU utilization. Try using efficient algorithms and data structures to reduce the computational complexity. Frequently, there is a tradeoff between faster processing/larger code size vs slower processing/smaller code size. Usually, optimizing a code for speed vs size is a better choice.

Event-Based Task Scheduling: Events are generated to trigger the system to perform some work. Once the processor finishes the requested task, it goes back to idle state allowing it to remain in low-power modes for longer durations. Incorporating sleep modes in the code putsthe processor or specific peripherals into low-power states during periods of inactivity. Use of efficient task scheduling algorithms minimizes wake-up times and ensures that tasks are executed in a power-efficient manner.

Optimized Data and I/O Access: Minimizing unnecessary data transfers and using efficient data structures to reduce power consumption during memory access operation such as unnecessary copying of data, especially when large blocks of memory are allocated. Reducing the frequency of I/O operations and using techniques such as batch processing to minimize power consumption during data transfers. Optimizing cache usage to minimize memory accesses and reduce power consumption associated with accessing external memory.

Code Profiling and Optimization: Profiling code to identify power-hungry sections and optimizing them to reduce power consumption without sacrificing performance is a major area for optimization. Additionally, compilers that optimize code for low-power execution can significantly reduce energy consumption by minimizing unnecessary operations and maximizing sleep modes utilization. Debugging tools that provide insights into power consumption behavior during development help identify and solve power inefficiencies early in the design process.

Using Low-Power Communication Protocols

The adoption of low-power communication protocols within embedded systems is paramount for achieving energy efficiency while maintaining reliable data transmission. This section aims to offer insights into energy-efficient communication standards and wireless protocols customized for low-power applications.

Wireless Protocols for Low-Power Design

Wireless communication is gaining popularity in embedded systems for its adaptability and scalability. However, without energy-efficient implementation, it can lead to considerable power consumption. Several wireless protocols, tailored for low-power applications, have emerged to address this concern, including:

• BLE is designed for low-power devices and applications with infrequent data transmission.
• NB-IoT technology is designed to provide low-power wide area network (LPWAN) connectivity for IoT devices. This means that NB-IoT devices have very low-power consumption compared to traditional cellular devices, which enables them to operate on a single battery charge for years.
• Z-Wave is a highly efficient and low-energy technology. While the smart home hub requires a constant power supply to keep the network up and running, many Z-Wave devices operate on battery power alone for a year or more before requiring replacement.
• LoRa is ideal for IoT applications requiring low data rate transmission over long distances.
• ZigBee is a low-power, low-data-rate wireless communication protocol commonly used in home automation and industrial control systems.

Conclusion

Tauro Technologies can dramatically reduce system cost, size, and power requirements through optimized hardware and software design, and meticulous component selection. Our expertise spans diverse fields including military, scientific, medical, industrial robotics, and communications. Contact us to explore how we can enhance your systems.