Advances in measurements and instrumentation leveraging embedded systems

The scope of this Special Topic is to collect contributions on the state of the art, history, and possible future development of embedded systems, highlighting the role of electronics and how the field of electronic measurements and instrumentation is influenced by these ubiquitous devices.

Traditionally, scientific instrumentation has been mostly computer-controlled. Nowadays, conventional benchtop instrumentation is unable to meet the needs of many modern applications that require paradigms such as portability, low latency, parallelization, re-configurability, networking, multi-platform compatibility, distributed (edge) processing, and low costs. With this in mind, embedded systems are revolutionizing the world of electronic measurements.

Among the different digital platforms, Microcontrollers (MCUs) and Field-Programmable Gate Arrays (FPGAs) have been largely leveraged in scientific instrumentation since decades, but recent advancements in their performance have been accelerating this trend, extending the range of functions.¹ In Ref. 1, the main motivations (compactness, re-configurability, parallelization, low latency for sub-ns timing, and real-time control) to adopt MCU and FPGA based embedded systems in scientific instrumentation are presented and discussed, in comparison to the traditional control paradigm based on the permanent interface of the instrument hardware with a personal computer (PC). In Ref. 1, relevant examples of applications in opto-electronics, physics experiments, and impedance, vibration, and temperature sensing from the recent literature are also reviewed to illustrate the potentiality of FPGAs and MCUs and the variety of their applications. The other papers can be divided into two groups: some, in fact, are focused on the field of instrumentation for sensing applications and others on the field of measurements for nuclear physics applications.

In recent years, in parallel with the improvement of the quality of life, especially in fast developing countries, the concern about air quality and its impact on human health has been growing. The pollutants in air contain particulate matter, in particular, heavy metals, and human beings exposed to air pollution for a long time may experience serious systemic diseases, such as pulmonary failure or Alzheimer’s disease. Therefore, it is of great importance to monitor the presence of heavy metal particles in air, but conventional methods have shortcomings such as high cost, slow response speed, low accuracy, and complex operation steps. In Ref. 2, a solution to detect particulate matter using magnetism is proposed based on the STM32F103 series microcontroller, which has the advantages of high performance, low power consumption, and strong expansibility, and it is capable of implementing non-contact measurement, which is convenient, efficient, and highly accurate. The whole detection system, capable of detecting particles with a diameter as low as 2 µm, is stable and efficient, and it presents the application value for the real-time rapid detection of heavy metal particles in both air and blood.

Not only heavy metals but also volatile organic compounds (VOCs) due to their toxic effects must be monitored. In Ref. 3, an electronic nose (eNose) device utilizing a set of commercial gas sensors of relatively low power consumption for VOC detection is presented. The setup utilizes a set of resistive gas sensors of divergent gas selectivity and sensitivity. Some of the applied sensors are commercially available, but prototype gas sensors could also be used. The unit is controlled by an embedded system M5Stack Core2 ESP32 IoT with touch screen and can be further developed by introducing wireless data transmission and computing for data classification. The recorded data are saved in a memory card for off-line processing. The developed setup can be upgraded to apply more advanced data processing by utilizing WiFi or Bluetooth connection. The control program was prepared using the Arduino IDE software environment and can be further advanced with ease. The applied materials and the established measurement procedure can use various air samples, having potential application in the food industry (e.g., detection of bio-agents emitted by bacteria, molds, and fungi) or medical check-ups (e.g., exhaled breath analysis).

In Ref. 4, a comprehensive review of the state of the art of Heating, Ventilation, and Air-Conditioning (HVAC) control sensing is carried out. This topic has broad impacts on society by affecting energy consumption, Earth’s climate, and the environmental health. The advancement in this field is strongly driven by the performance of the embedded systems exploited as sensors and their beneficial features. In addition to summarizing the state of the art of the adopted indoor solutions, with the purpose of fueling and focusing the research effort on this important topic, particular attention was paid to the identification of new possible development; e.g., the RAdio Detection And Ranging (RADAR) technology has been identified as the emerging one in this field.

In Ref. 5, the latest developments in LiDAR (Light Imaging Detection And Ranging) technology are reviewed; currently, LiDAR technology is considered of great interest as it is widely employed in a variety of application fields, such as automotive industry, seismology, archaeology, metrology, and military. In Ref. 5, the typical architecture of a LiDAR system is described; some of the most typical areas of recent application of LiDAR systems are reported and the most recent FPGA-based architectures aimed at improving some computational post-processing tasks in LiDAR systems are presented.

In a few applications,⁶ due to the high cost of LiDAR systems, a single-pixel system would be the best solution, with fast processing times and multi-wavelength operating capabilities that can be adapted for rapid detection and classification applications, where it is sufficient to detect signals of characteristic intensity without doing the image reconstruction. In Ref. 6, the single-pixel algorithm is leveraged by parallel implementations on the FPGA and Graphics Processing Unit (GPU), thus enabling 3D applications near real-time, and moreover, the evolution of the conventional algorithms toward the artificial intelligence field such as machine learning is assessed. The single-pixel approach offers the possibility to create a new low-cost sensing technology for all those applications requiring low-cost sensors to be used in outdoor environments with harsh conditions and to be carried by unmanned systems. Nevertheless, the single-pixel technology is not only limited to be used as a vision sensor for vehicles or unmanned aerial vehicles, but there are also other fields of application, such as medicine, RADAR, LiDAR, space exploration, Virtual Reality/ Augmented Reality (VR/AR), and Remotely Operated Vehicles (ROV) system.

Experiments in atomic, molecular, and optical (AMO) physics are often a combination of a large number of commercial or custom-made instruments from different sources and manufacturers that need to operate synchronously and in a repeatable mode. Synchronization is a crucial issue in AMO experiments, and a few approaches are adopted as control strategies. For example, a reliable approach is to use a programmable system on chip (PSoC), which combines an FPGA and a high performance microprocessor on a single chip. This allows implementation of operating systems, advanced communication protocols, and high level language interpreters in the microprocessor, leveraging the FPGA when hardware acceleration or control of dedicated peripherals is needed. In Ref. 7, the PSoC-based primary clock device designed and developed for controlling AMO physics experiments is easily integrated with the Labscript suite. The hardware provides 64 buffered digital outputs for controlling other hardware devices and also four input trigger channels. The printed circuit board design ensures signal integrity and minimal crosstalk between channels. The firmware design implements a state machine written in SystemVerilog and a ping-pong memory controller that allows the execution of a large number of instructions (exceeding 8 192 000). The system is currently being used to run the entire experiment in a laboratory, providing triggers for digital to analog converters (DACs), digital direct synthesizers (DDSs), mechanical shutters, and many other instruments. The versatility of the platform also allows for other modifications, such as the possibility to add additional instructions to the state machine. Further modifications to the design might include network security protocols and encryption for data transmission, which have not been included so far since the setup is running on an isolated network.

LAILA⁸ is a miniaturized eight-channel electronic readout system for compact γ-ray detectors, combining high-resolution spectroscopy capability with position sensitivity. Compactness is achieved by the combination of a novel CMOS front-end ASIC (Application-Specific Integrated Circuit) for analog processing of a large signal current from Silicon PhotoMultiplier (SiPM) solid-state photodetectors, with a simple MCU managing data acquisition, transmission, and gain stabilization. The adoption of automatic gain regulation in the gated-integrator stage of the ASIC offers an 84 dB dynamic range, combining single-photon sensitivity with an extended input photon energy range (20 keV to 4 MeV using 30 μm-cell SiPMs). Using this module with properly merged 144 SiPM pixels coupled to a 3 in.-thick lanthanum bromide scintillation crystal, 3% energy resolution at 662 keV and 1 cm spatial resolution in the estimation of the interaction coordinates are experimentally demonstrated in this work. These results are in line with the state of the art and outperform other low-cost MCU-based implementations. Beyond its application in nuclear physics, such a versatile instrument can find widespread adoption in educational, environmental, and security applications.

The purpose of this Special Topic was to highlight the role of embedded systems in the field of scientific instrumentation and electronic measurements. The modern paradigms required by many applications make conventional measurement systems inefficient, and terms such as low cost, compatibility, re-configurability, low latency, and parallelization are increasingly widespread among the specifications required for new measuring instruments. Altogether, the selected contributions contained in this Special Topic illustrate the great potentiality of embedded systems that stand out as optimal solutions in various interdisciplinary applications, with important repercussions not only in the scientific and industrial fields but also with a great impact on society and on the quality of life.

We acknowledge all the authors for their novel and insightful contributions to the Special Topic, as well as the reviewers, who made numerous helpful comments and suggestions that strengthened all the articles. We also appreciate the kindness, patience, and professionalism of the editorial staff, especially Alexandra Giglia and Mehdi Torbati, as well as the Associate Editor Nikolai Beev and the Editor-in-Chief Richard Pardo, all of whom provided unfailing support through every step of the process.

The authors have no conflicts to disclose.