Ultra-low Power Microcontroller Research Articles

Towards Energy-Efficient Heterogeneous Multicore Architectures for Edge Computing

In recent years, the edge computing paradigm has been attracting much attention in the Internet-of-Things domain. It aims to push the frontier of computing applications, data, and services away from the usually centralized cloud servers to the boundary of the network. The benefits of this paradigm shift include better reactivity and reliability, reduced data transfer costs toward the centralized cloud servers, and enhanced confidentiality. The design of energy-efficient edge compute nodes requires, among others, low power cores such as microprocessors. Heterogeneous architectures are key solutions to address the crucial energy-efficiency demand in modern systems. They combine various processors providing attractive power and performance trade-offs. Unfortunately, no standard heterogeneous microcontroller-based architecture exists for edge computing. This paper deals with the aforementioned issue by exploring typical low power architectures for edge computing. Various heterogeneous multicore designs are developed and prototyped on FPGA for unbiased evaluation. These designs rely on cost-effective and inherently ultra-low power cores commercialized by Cortus SA, a world-leading semiconductor IP company in the embedded ultra-low power microcontroller domain. Some microarchitecture-level design considerations, e.g., floating point and out-of-order computing capabilities, are taken into account for exploring candidate solutions. In addition, a tailored and flexible multi-task programming model is defined for the proposed architecture paradigm. We analyze the behavior of various application programs on available core configurations. This provides valuable insights on the best architecture setups that match program characteristics, so as to enable increased energy-efficiency. Our experiments on multi-benchmark programs show that on average 22% energy gain can be achieved (up to 45%) compared to a reference system design, i.e., a system with the same execution architecture, but agnostic of the task management insights gained from the comprehensive evaluation carried out in this work.

Four-PAM Modulation of Ambient FM Backscattering for Spectrally Efficient Low-Power Applications

Ambient backscatter uses radio frequency signals available in the environment (e.g., radio broadcasting, television, or mobile telephony) to transmit data effectively leading to significant energy and cost efficiency increase. This paper presents a novel wireless tag, which for the first time utilizes 4-pulse amplitude modulation technique to modulate the ambient backscattered FM signals in order to send data to a nearby low-cost software defined radio reader. The tag is based on an RF front-end that uses a single transistor controlled by an ultralow-power microcontroller. The microcontroller includes an analog-to-digital converter for sensing and a digital-to-analog converter for RF front-end control. A proof-of-concept prototype is demonstrated in an indoor environment with the low bit rate of 345 b/s and power consumption $27~\mu \text{W}$ . It operated using a real FM station at 34.5 km away and the tag-to-reader distance was tested at 1 m. The value of energy spent in this modulator was 78.2 nJ/bit at 345 b/s and 27.7 nJ/bit at 10.2 kb/s.

A Hysteretic Buck Converter With 92.1% Maximum Efficiency Designed for Ultra-Low Power and Fast Wake-Up SoC Applications

This paper presents a dc–dc converter for integration in the power management unit of an ultra-low power microcontroller. The converter is designed to significantly reduce the wake-up energy and startup delay of the supplied core. The use of a minimized output capacitor is the key factor to save the wake-up energy. The converter is buffered with only 56 nF and guarantees a stable output of 1.2 V with a voltage ripple smaller than 30 mV. The controller of the proposed dc–dc converter is based on a predictive peak current control that allows the system to control the energy transfer at extremely low power consumption. The proposed circuit is implemented in 130-nm CMOS technology with an area of only 0.14 mm2. It achieves a high conversion efficiency of 92.1% and a small quiescent current of 440 nA. It operates from 1.8 to 3.3 V with a maximum load of 2.65 mA.

Design of Multi-functional Physiological Signal Acquisition and Wireless Transmission System

The design is based on the ultra-low power microcontroller MSP430. It is designed and developed to measure the temperature and heart rate pulse and blood flow velocity by using temperature sensor, ultrasonic module, heart rate pulse detection sensor, global satellite positioning module, global mobile communication system and wireless transmission module. Anti-lost wireless transmission system. The terminal through the positioning system, the temperature sensor pulse detection sensor and the ultrasonic module to obtain the location information and physical health of the elderly, and then in the form of short messages sent to the GSM through the SMS to receive the phone terminal, to achieve the location of the elderly and their physical condition more comprehensive Real-time monitoring, but also through the Bluetooth data upload to the database, to achieve the data storage and analysis.

Ambient Backscatterers Using FM Broadcasting for Low Cost and Low Power Wireless Applications

Nowadays, the explosive growth of Internet-of-Things-related applications has required the design of low-cost and low-power wireless sensors. Although backscatter radio communication is a mature technology used in radio frequency (RF) identification applications, ambient backscattering is a novel approach taking advantage of ambient signals to simplify wireless system topologies to just a sensor node and a receiver (RX) circuit eliminating the need for a dedicated carrier source. This paper introduces a novel wireless tag and RX system that utilizes broadcast frequency modulated (FM) signals for backscatter communication. The proposed proof-of-concept tag comprises of an ultralow-power microcontroller (MCU) and a RF front-end for wireless communication. The MCU can accumulate data from multiple sensors through an analog-to-digital converter, while it transmits the information back to the RX through the front-end by means of backscattering. The front-end uses ON–OFF keying modulation and FM0 encoding on ambient FM station signals. The RX consists of a commercial low-cost software-defined radio which downconverts the received signal to baseband and decodes it using a suitable signal processing algorithm. A theoretical analysis of the error rate performance of the system is provided and compared to bit-error-rate measurements on a fixed transmitter-tag-RX laboratory setup with good agreement. The prototype tag was also tested in a real-time indoor laboratory deployment. Operation over a 5-m tag-reader distance was demonstrated by backscattering information at 2.5 kb/s featuring an energy per packet of $36.9~\mu \text{J}$ .

Bespoke processors: A new path to cheap chips [News

"Processors are overdesigned for most applications," says Rakesh Kumar, an associate professor of electrical and computer engineering at the University of Illinois. It's a well-known and necessary truth: In order to have programmability and flexibility, there's simply going to be more stuff on a processor than any one application will use. That's especially true of the type of ultralow-power microcontrollers that drive the newest embedded computing platforms such as wearables and Internet of Things sensors. These are often running one fairly simple application and nothing else (not even an operating system), meaning that a large fraction of the circuits on a chip never, ever see a single bit of data.

A Long-Distance RF-Powered Sensor Node with Adaptive Power Management for IoT Applications

We present a self-sustained battery-less multi-sensor platform with RF harvesting capability down to −17 dBm and implementing a standard DASH7 wireless communication interface. The node operates at distances up to 17 m from a 2 W UHF carrier. RF power transfer allows operation when common energy scavenging sources (e.g., sun, heat, etc.) are not available, while the DASH7 communication protocol makes it fully compatible with a standard IoT infrastructure. An optimized energy-harvesting module has been designed, including a rectifying antenna (rectenna) and an integrated nano-power DC/DC converter performing maximum-power-point-tracking (MPPT). A nonlinear/electromagnetic co-design procedure is adopted to design the rectenna, which is optimized to operate at ultra-low power levels. An ultra-low power microcontroller controls on-board sensors and wireless protocol, to adapt the power consumption to the available detected power by changing wake-up policies. As a result, adaptive behavior can be observed in the designed platform, to the extent that the transmission data rate is dynamically determined by RF power. Among the novel features of the system, we highlight the use of nano-power energy harvesting, the implementation of specific hardware/software wake-up policies, optimized algorithms for best sampling rate implementation, and adaptive behavior by the node based on the power received.

Feasibility Study for Unconstrained Respiration Monitoring Based on Multi-Way Approach Using an Acceleration and Force Sensing Module

The purpose of this paper was to validate the feasibility of a proposed sensing module for multiway respiratory monitoring. The proposed monitoring system was implemented using an ultralow-power microcontroller, that included a three-axis accelerometer, an analog/digital input port to connect to an external sensor, and a Bluetooth module for wireless communication. We developed an accelerometer-equipped wireless sensing module and a layered-architecture external strip-type force sensor interface for respiration monitoring. In the feasibility experiment, the accelerometer-equipped module was inserted in a pillow and strip-type force sensors were placed under each of the head, chest, and abdomen to investigate the performance of the respiration measurement in terms of the measurement position. Twelve subjects participated in the experiment, and signals from the accelerometer and the strip-type force sensor were simultaneously recorded during sleep. The results of the experiment showed that the deviation in length of the respiration cycle was estimated with errors under 250 ms in the acceleration signal and the signal from the strip force sensors.

English

Wireless sensor network based applications have gained a significant importance in recent years. However, it creates problems when sending the detected data over distant stations even though establishment of sensor networks by means of ZigBee communication modules as the communication range of these modules are limited. For this reason, in this study, design of a gateway node which can be used in the sensor network applications was developed. The gateway node developed consists of a CC2530 ZigBee Module, an MSP430G2553 ultra low power microcontroller and a SIM900 GSM/GPRS module. As a result of this node, the sudden changes can be sent as data packets (SMS), also, the data can easily be monitored on web based and mobile platforms. It is anticipated that the study will be useful for the researchers conducting sensor network applications. Key words: Wireless sensor networks, ZigBee, sensor node, gateway node.

A new gateway node for wireless sensor network applications

Wireless sensor network based applications have gained a significant importance in recent years. However, it creates problems when sending the detected data over distant stations even though establishment of sensor networks by means of ZigBee communication modules as the communication range of these modules are limited. For this reason, in this study, design of a gateway node which can be used in the sensor network applications was developed. The gateway node developed consists of a CC2530 ZigBee Module, an MSP430G2553 ultra low power microcontroller and a SIM900 GSM/GPRS module. As a result of this node, the sudden changes can be sent as data packets (SMS), also, the data can easily be monitored on web based and mobile platforms. It is anticipated that the study will be useful for the researchers conducting sensor network applications. Key words: Wireless sensor networks, ZigBee, sensor node, gateway node.

Hardware Accelerator for Probabilistic Inference in 65-nm CMOS

A hardware accelerator is presented to compute the probabilistic inference for a Bayesian network (BN) in distributed sensing applications. For energy efficiency, the accelerator is operated at a near-threshold voltage of 0.5 V, while achieving a maximum clock frequency of 33 MHz. Clique-tree message passing algorithm is leveraged to compute the probabilistic inference. The theoretical maximum size of a factor that the proposed hardware accelerator can handle is $2^{(8\times 20)=160}$ entries, which is sufficient for handling massive BNs, such as PATHFINDER, MUNIN, and so on (>1000 nodes). A Logical Alarm Reduction Mechanism (ALARM) BN is used to benchmark the performance of the accelerator. The accelerator consumes 76 nJ to execute the ALARM network using a clique-tree message-passing algorithm, while the same algorithm executed on an ultralow-power microcontroller consumes 20 mJ.

Novel Design Concept of an Optoelectronic Integrated RF Communication Module

This contribution presents a novel design concept of a 24 GHz radio frequency communication module. The integration of optical and electrical components is a particular challenge since the module is miniaturized in order to be integrated into any metallic workpieces. The design concept and the scope of functions of the communication unit acting as a wireless sensor node are discussed. The development of a highly integrated radio frequency circuit and the realization of through glass vias are some main aspects. The central control unit is an ultra-low power microcontroller capable of a flexible connection of sensors. By using an energy harvesting concept consisting of a solar cell with an efficiency of 40% and a supercapacitor the availability of energy is unlimited. Different lighting conditions are investigated in order to evaluate the available power of the solar cell. Furthermore, the power supply is investigated concerning voltage-current characteristics and the resulting operating time of the whole unit for a low ambient light scenario.

Design and Implement of an Indoor Location System Based on Active RFID

This paper presents an indoor location system. The system is comprised of a RFID reader and several low-power active RFID tags.This designed active RFID tag consists of an ultra low power micro-controller, a low power RF transceiver, micro-strip antenna and an on-board battery. The indoor location system uses a RSSI-based ranging technology location algorithm. The experimental results show that the system is a good location system of high precision. And thanks to the advantage of these low-power active RFID tags, this system can be implemented simply for different applications.

Separate Clock Network Voltage for Correcting Random Errors in ULV Clocked Storage Cells

This brief presents an implementation of ultralow-power microcontrollers that use a separate clock network voltage (SCNV) to correct unexpected errors produced by on-chip variations (OCVs). Separating the clock network voltage requires amendments in the standard cell library and physical designs. Here, the experiments used a 65-nm technology that exhibited considerable OCVs, which caused write and retention errors in clocked storage cells and limited the voltage scaling of microcontrollers. Using the SCNV provides an extraordinary operability to correct errors in the low-voltage clocked storage cells. In addition, the area overhead of the proposed implementation is negligible. Applying the SCNV, the measurement results indicate that the microcontrollers can be operated below 0.3 V, over 0.15-V extension in voltage scaling, and achieve the optimal energy consumption at 0.34 V. Separating the clock network voltage has tradeoff issues in system timing and energy consumption based on the measurement results, and this brief discusses proper applications.

Autonomous Control System for a Squeeze Mode Mr Vibration Isolator in an Automotive Engine Mount

Abstract The investigated autonomous control system for a squeeze mode magnetorheological (MR) vibration isolator is based on an ultra-low power microcontroller MSP430F5529. The design structure of the control system and the dedicated real-time system are briefly presented and the laboratory testing data are summarised.

RAMSES: RFID Augmented Module for Smart Environmental Sensing

This paper presents a radio frequency identification (RFID) augmented module for smart environmental sensing (RAMSES), which is a fully passive device with sensing and computation capabilities conceived to explore novel and unconventional RFID applications. RAMSES implements an RF energy-harvesting circuit enhanced by a dc-dc voltage booster in silicon-on-insulator technology, an ultralow-power microcontroller, temperature, light, and acceleration sensors, and a new-generation ${\rm I}^{2}{\rm C}$ -RFID chip to wirelessly deliver sensor data to standard RFID EPCglobal Class-1 Generation-2 readers. A preliminary RAMSES prototype, fabricated on a printed circuit board using low-cost off-the-shelf discrete components, has been extensively tested through experiments conducted both in lab and real-world application scenarios. The achieved results have demonstrated the ability of RAMSES to harvest the RF energy emitted by an interrogator placed up to 10 m of distance and autonomously perform sensing, computation, and data communication. To our knowledge, this is the longest range ever reported for fully passive RFID sensors. Furthermore, for applications requiring larger operating distances, RAMSES provides also a battery-assisted passive mode yielding up to 22-m communication range.

The Design of Portable Granary Thermometer

This article designed a portable granary thermometer to solve the shortcomings of present similar products ,such as complex structures , high performance price ratio and lack of flexibility , this thermometer used ultra-low power microcontroller MSP430F149 and programmable temperature sensor DS18B20 as the main components, it can collect, display and store the temperature on a real-time basis . Based on actual use, this apparatus possess the advantage of complete function, low power consumption, easy to operate, low price, portable and wide occasions of application etc.

Frequency-Variance Based Antistrong Vibration Interference Method for Vortex Flow Sensor

Vortex flowmeter is apt to be disturbed by pipe vibration in industrial applications. It is a very difficult problem to be solved, and affects the applications of vortex flowmeter. To solve this key problem, the frequency features of the flow signal and vibration noise are analyzed. A frequency-variance algorithm is proposed to deal with the vortex flow sensor output signal. A variance threshold is set to distinguish the vortex flow signal from the vibration noise interference. A signal processing system based on an ultralow-power microcontroller is developed to implement the algorithm and to extract the flow rate information from the signal containing strong vibration noise. At the same time, this system meets the requirements of low-power and two-wire mode, and can be used in process control. The strong vibration experiments are conducted to validate the effectiveness of both antistrong vibration algorithm and the system. Only one vortex flow sensor is required in the vortex flowmeter, which avoids the design and installation of the vibration sensor and saves the costs of meter.

Low‐cost flexible thin‐film detector for medical dosimetry applications

The purpose of this study is to characterize dosimetric properties of thin film photovoltaic sensors as a platform for development of prototype dose verification equipment in radiotherapy. Towards this goal, flexible thin‐film sensors of dose with embedded data acquisition electronics and wireless data transmission are prototyped and tested in kV and MV photon beams. Fundamental dosimetric properties are determined in view of a specific application to dose verification in multiple planes or curved surfaces inside a phantom. Uniqueness of the new thin‐film sensors consists in their mechanical properties, low‐power operation, and low‐cost. They are thinner and more flexible than dosimetric films. In principle, each thin‐film sensor can be fabricated in any size (mm2 – cm2 areas) and shape. Individual sensors can be put together in an array of sensors spreading over large areas and yet being light. Photovoltaic mode of charge collection (of electrons and holes) does not require external electric field applied to the sensor, and this implies simplicity of data acquisition electronics and low power operation. The prototype device use for testing consists of several thin film dose sensors, each of about 1.5 cm×5 cm area, connected to simple readout electronics. Sensitivity of the sensors is determined per unit area and compared to EPID sensitivity, as well as other standard photodiodes. Each sensor independently measures dose and is based on commercially available flexible thin‐film aSi photodiodes. Readout electronics consists of an ultra low‐power microcontroller, radio frequency transmitter, and a low‐noise amplification circuit implemented on a flexible printed circuit board. Detector output is digitized and transmitted wirelessly to an external host computer where it is integrated and processed. A megavoltage medical linear accelerator (Varian Tx) equipped with kilovoltage online imaging system and a Cobalt source are use to irradiate different thin‐film detector sensors in a Solid Water phantom under various irradiation conditions. Different factors are considered in characterization of the device attributes: energies (80 kVp, 130 kVp, 6 MV, 15 MV), dose rates (different ms × mA, 100–600 MU/min), total doses (0.1 cGy‐500 cGy), depths (0.5 cm–20 cm), irradiation angles with respect to the detector surface (0°‐180°), and IMRT tests (closed MLC, sweeping gap). The detector response to MV radiation is both linear with total dose (~1‐400 cGy) and independent of dose rate (100‐600 Mu/min). The sensitivity per unit area of thin‐film sensors is lower than for aSi flat‐panel detectors, but sufficient to acquire stable and accurate signals during irradiations. The proposed thin‐film photodiode system has properties which make it promising for clinical dosimetry. Due to the mechanical flexibility of each sensor and readout electronics, low‐cost, and wireless data acquisition, it could be considered for quality assurance (e.g., IMRT, mechanical linac QA), as well as real‐time dose monitoring in challenging setup configurations, including large area and 3D detection (multiple planes or curved surfaces).PACS number: 87.56.Fc

Design of Side Line Short Circuit Detection Device Load of Low Voltage Circuit Breaker before Closing

It uses MSP430F2274, the ultra low power microcontroller, as the control core of short circuit detection device, through the accurate measurement of low voltage circuit breaker load side of the main wiring of insulation resistance value and the interphase insulation resistance value, outputting high voltage startup sound and light alarm device, and then accomplish the open circuit fault detection. Testing power supply is the use of magnetic coupling resonance principle, from the main power grid electrical insulation for short circuit detection device. The device has the advantages of low cost, small volume, good safety, good detection effect, and can be embedded in use in low voltage circuit breaker.