NSF-BSF: CNS Core: Small: Reliable and Zero-Power Timekeepers for Intermittently Powered Computing Devices via Stochastic Magnetic Tunnel Junctions

该项目旨在推进低功耗、无电池、能量收集嵌入式系统的计时技术。这些系统必须在多个频繁的电源故障中执行计算和传感任务。这种间歇性操作需要很强的时间感，以确保没有能量浪费，计算结果不会过时。现有的计时器（即实时时钟）需要大量的能量来开启和操作，相对较大（毫米尺度），重启缓慢，并且使用与电源故障的长度成比例的能量（其可能是不切实际的长）。该项目利用新兴的纳米级非易失性磁性随机存取存储器（MRAM）器件的独特性能，特别是可调节的数据保持长度，以创建数量级更低的功耗，可调节的超小型计时设备。 一个系统可以设置计时器的几个比特，然后检查它们，看看哪些比特丢失了信息。通过将每个位或位阵列定制为特定的时间长度，系统可以测量时间，而不管是否发生电源故障。这种计时器需要相同数量的能量，如果它计时一秒，一天或一年的中断，根据所使用的磁性元件的数量和特性，具有任意精度。该项目跨越系统堆栈，以实现这个计时器的好处;探索电路设计，架构和系统范例，将这种新的计时设备嵌入到间歇性计算的背景下：作为运行时时钟，中断源，数据和输入/输出（I/O）控制器的替代品，并作为过期的内存分配器。这些模块可供应用程序开发人员使用，以提高其程序的时效性。本项目开发的技术将为一类重要的新兴计算机系统提供更有效和更准确的计时。无电池和能量收集计算设备为物联网提供了一个更可持续的未来，并实现了许多健康，农业和智能基础设施应用。在远程供电传感器中消除电池将减少因电池磨损和更换而造成的日益增长的废物流。该项目的设备和系统的制造和最终分销将为未来的无电池系统提供更准确的计时模块，提高无电池系统的可靠性，安全性和及时性。由此产生的工具和实验结果将使强大的跨堆栈模拟的无电池设备和制造方法的磁存储器设备。这个项目的成果将被整合到几个正在进行的推广活动，使K-12和本科生接触到嵌入式计算的使用和应用。这项工作将培养研究生在计算，材料和物理方面的基本技能，并通过GoBabyGo让他们参与指导，教学和推广活动！- 在那里，学生们帮助建立电动轮椅从乘坐玩具汽车的儿童行动不便的问题。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This project seeks to advance the state-of-the-art in timekeeping for low-power, battery-free, energy harvesting embedded systems. These systems must perform computation and sensing tasks across multiple, frequent power failures. This intermittent operation requires a strong sense of time to ensure no energy is wasted and computed results are not stale. Existing timekeepers (i.e. real-time clocks) require significant amounts of energy to turn on and operate, are relatively large (millimeter scale), are slow to restart, and use energy proportional to the length of a power failure (which can be impractically long). This project takes advantage of the unique properties of emerging nano-scale non-volatile magnetic random-access memory (MRAM) devices, particularly adjustable data retention length, to create orders of magnitude lower power, adjustable, ultra-small timekeeping devices. A system can set a few bits of the timekeeper and check them later to see which ones have lost information. By tailoring each bit, or array of bits, to particular lengths of time, the system can measure time regardless of whether a power failure occurred. Such a timekeeper requires the same amount of energy if it times an outage of one second, one day, or one year, with arbitrary accuracy depending on the number and characteristics of the magnetic elements used. The project cuts across the system stack to realize the benefits of this timekeeper; exploring circuit designs, architectural, and system paradigms to embed this new timekeeping device in the context of intermittent computing: as an alternative to a runtime clock, an interrupt source, a data and input/output (I/O) controller, and as an expiring memory allocator. These modules are made available to application developers to enhance the timeliness of their programs.The technologies developed in this project will enable more efficient and accurate timekeeping for an important emerging class of computer systems. Batteryless and energy harvesting computing devices offer a more sustainable future for the Internet of Things and enable numerous health, agriculture, and intelligent infrastructure applications. The elimination of batteries in remotely powered sensors will mitigate the growing waste stream resulting from battery wear out and replacement. The fabrication and eventual distribution of the devices and systems from this project will provide a more accurate timekeeping module for future batteryless systems, enhancing the reliability, security, and timeliness of batteryless systems. The resulting tools and experimental results will enable robust cross-stack simulation for battery-free devices and fabrication methods for magnetic memory devices. Outcomes of this project will be integrated into several ongoing outreach activities that expose K-12 and undergraduate students to the usage and application of embedded computing. This effort will train graduate students in essential skills across computing, materials, and physics and engage them in mentoring, teaching, and outreach activities via GoBabyGo!– where students help build power wheelchairs from ride-on toy cars for children with mobility issues.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.