Tinkering with Time

Protocols and Programming

Many embedded systems need to make use of synchronized time information. In this article, Jeff explores the history of time measurement and how it has led to NTP and other modern technologies for coordinating universal date and time. Using Arduino and the Espressif System’s ESP32, Jeff then goes through the steps needed to enable an embedded system to request, retrieve and display the synchronized date and time to a display.
(Caption for lead image Figure 1: Time zone boundaries are flexible, shifted locally to keep territories from being divided wherever possible..

By Jeff Bachiochi

It’s been said that ”If you are on time, you’re late,” or, “To be early is to be on time.” It’s all relative. If you go to a meeting and people are already there, you feel as if you are late. If you are the first to arrive, you wonder if you’ve got the schedule wrong, and then you check your watch or phone for the time. Time can be troublesome for us, because the present is an ever-changing instant where the past meets the future. We cruise through life when all players reference the same moment, but should we become out of sync, the ride gets bumpy.

We can imagine that in humanity’s early times the first concepts of time were cyclic periods—like day/night, seasons and life/death. Our fundamental measurement of a day directly relates to our life and history, and seems to tie all nature together. But what about those activities that occur within the confines of each day? Some way of defining the parts of a day were needed. At the time, we had one division—day/night—with most considering the start of a day to be daybreak or sunrise, and the start of night to be sunset.

Since daytime was directly related to the sun’s position, the day could be divided into two parts based on whether the sun was rising in the sky or falling back toward the horizon. Observing the sun’s shadow gave way to the first sundials, which provided a visual indication of time relative to sunrise and sunset without physical divisions. One such division of the day was religious in origin: canonical hours or periods of fixed prayer at regular intervals were defined in monastic communities. At that time, our understanding of the sky was astrological and not astronomical. The latter would eventually define the breakdown of a day into hours, minutes and seconds.

For the most part, the hour was a variable concept. Around the 14th century, 12 was chosen as a practical division of the day (and the night) into equal parts. It was the most convenient number for dividing into fractions because it’s divisible by 2, 3 and 4—thus giving us the 24-hour day we use today. Without the sun, sundials were worthless, so other means of recording the passage of time were invented, including water, candles and weights. These and early mechanical clocks of the 16th century were not accurate, because their mechanisms were essentially unregulated. It wasn’t until the next century that the pendulum gave the mechanical clock accuracy to within 1 minute a day. Today, we have access to extremely accurate clocks. Atomic clocks measure an atom’s fluctuating energy levels to produce an accuracy of ± 1 second in over a billion years.

Time Keeper

The International Bureau of Weights and Measures (called Bureau International des Poids et Mesures or BIPM in France) is an intergovernmental organization that was established to oversee measurement science and measurement standards. One important role for the BIPM is maintaining the accuracy of worldwide time of day. It combines, analyzes and averages the official atomic time standards of member nations around the world, to create a single, official Coordinated Universal Time (UTC). The Royal Observatory, Greenwich, England was chosen as the reference point to define the Universal day, counted from 0 hours at mean midnight, as used on the island since 1847. By 1884, the Greenwich Meridian was used for two-thirds of all charts and maps as their Prime Meridian. The world is divided into 24 time zones, each 15 degrees in width (24 hr/360 degrees). However, as shown in Figure 1, time zone boundaries are shifted to prevent a country from being needlessly split into separate zones.

All time on earth is related to the official time in Greenwich, England by denoting a time zone offset. Current civil time can be determined by adding or subtracting the UTC offset (number of hours and minutes). This ranges from UTC−12:00 in the west to UTC+14:00 in the east. Table 1 lists those offsets that relate to the United States.
The US spans seven time zones. When a time zone uses daylight saving time, the ST for Standard Time is replaced by DT indicating Daylight Saving Time. Daylight Saving Time increases the regional offset by 1:00, and was implemented to shift daylight activities during the longer summer hours. Daylight Saving Time is a local shift that must be handled locally, and as such does not affect the UTC in any way.

Table 1
Time zone offsets are listed here for the US daylight saving times have an additional offset of 1 hour and must be accounted for locally.

In my youth I recall the phone company providing a number you could to call to hear the current time. The first radio station, WWV in Colorado, morphed into National Institute of Standards and Technology (NIST), whose broadcast focused on developing frequency standards and eventually broadcasting time and frequency information on the 2.5-, 5-, 10-, 15- and 20-MHz shortwave bands. Today, the time is available almost everywhere, and that time is synchronized to the UTC, all thanks to the Internet.

National Standard Time

The Network Time Protocol (NTP) is used to synchronize our clocks via the Internet. The NTP architecture, protocol and algorithms provide a nominal accuracy of tens of milliseconds on WANs, sub-milliseconds on LANs, and sub-microseconds using a precision time source such as a cesium oscillator or GPS receiver. Reliability is assured by redundant tiered servers and diverse network paths. The “NTP pool” is a dynamic collection of networked computers that volunteer to provide highly accurate time via the NTP to clients (like us) worldwide. We can use one of the NTP pool servers to get UTC information. Although using the NTP protocol will assure the accuracies listed above, this is often unnecessary and overly complicated for those applications that are only interested in whole-second times for RTC (Real Time Clocks). SNTP, a simplified subset of the NTP protocol, generally is sufficient for our needs.

Figure 2
This is the format of the 48 byte packet sent to and from NTP servers. We can get away with sending a packet of “zero” data, except for the first byte as a request. A received packet will contain the total seconds since the Epoch located in the first four bytes of the Transmit Timestamp.

SNTP uses a UDP connection to send a datagram or packet, as opposed to a TCP connection. The basic transaction is simple. We send an SNTP data structure as a UDP packet using port 123 to the server. The time server (one of the NTP pool) then sends back an SNTP data structure as a UDP packet. That’s it! The structure of the datagram consists of four 32-bit words (4 × 32 bits = 128 bits or 16 bytes), followed by four 64-bit time stamps (4 × 64 bits = 256 b or 32 bytes) as shown in Figure 2. There can be optional data, but we won’t need it. In fact, we need only to worry about the first byte of the (16 bytes + 32 bytes = 48 bytes) datagram to make a request.

This is set according to RFC 4330:

LeapsecondInformation 2 bits = “00” disregarded
             VersionNumber 3 bits = “100” 4
                        MODE 3 bits = “011” Client
Therefore:
First Byte = “00100011” or 0x23

The returned datagram will be in the same format. The time stamps we sent as zeros could have been used to determine the actual propagation delay in the message trip, to calculate an accurate sub-second synchronized time. We are not concerned with that level of accuracy. However, we do want to get the time from the server, and that will be populated in the last of the four time stamps in the reply. So how does this time stamp relate to the present second, minute, hour, day, month and year? Sad to say, it does not specify any of those. This time stamp gives the number of seconds from 0:00 on 1 January 1900. …

Read the full article in the February 343 issue of Circuit Cellar
(Full article word count: 3269 words; Figure count: 5 Figures.)

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New Certified Service Regulates V2X-Connected Vehicles

INTEGRITY Security Services (ISS), a subsidiary of Green Hills Software, has announced the ISS Misbehavior Authority Service (MAS), which is the first MA Service for the US V2X ecosystem. The ISS MAS will begin by serving the US Department of Transportation’s Connected Vehicle Pilots already subscribing to the ISS Certificate Management Service (CMS) and all other ISS CMS Subscribers. As the de facto US national SCMS Manager, ISS continues to ensure the US V2X ecosystem is secure and interoperable, according to ISS.

With the ISS MAS, CV-Pilots and ISS CMS Subscribers will be able to begin identifying vehicles for misbehavior and removing them from their networks. Device manufacturers and all ISS CMS Subscribers should contact ISS by registering to discuss how to get their devices ISS CMS-certified, enabled with the ISS-approved MAS OBU client and begin testing. Developers who are are running a DSRC and/or C-V2X AV or CV-Pilot and have potential misbehavior data they want analyzed can register with the service.

The ISS MAS extends the initial work in misbehavior detection performed by ISS, CAMP and USDOT. The ability to identify vehicles that are not sending correct V2X messages and to remove them from the connected vehicle ecosystem is an important security requirement to maintain trust in the ecosystem. The ISS MAS provides this capability on a scalable and efficient national level. As part of this, ISS will be publishing its misbehavior detection criteria, reporting format and MAS APIs for OBU and RSU vendors to use with their compliant systems.

INTEGRITY Security Services | www.ghsiss.com

 

 

Secure Cellular Router Serves Industrial and Transportation Needs

Digi International has announced the Digi WR54, a rugged, secure, high-performance wireless router for complex mobile and industrial environments. With dual cellular interfaces, Digi WR54 provides immediate carrier failover for near-constant uptime and continuous connectivity, especially as vehicles move throughout a city or for locations with marginal cellular coverage. Together with a hardened milspec-certified design and built-in Digi TrustFence security framework, this LTE-Advanced router is designed specifically to meet the connectivity challenges inherent in multi-location, on-the-move conditions, from rail and public transit to trucking fleets and emergency vehicle applications.

LTE-Advanced technologies with carrier aggregation are pushing theoretical download speeds to 300 Mbps, and the next generation of cellular radios is capable of aggregating three or more channels for capabilities up to 600 Mbps. It’s expected that 5G deployments this year will push the demands for performance and edge computing even further. Digi WR54 provides an LTE-Advanced cellular module built on a platform that supports higher speeds to optimize bandwidth today while also being positioned for the future as network capabilities improve.

Multiple transit system use cases require rugged, reliable, high-speed connectivity solutions to carry mission-critical data and communications. Transit system integrators require connectivity for fleet tracking, logistics, engine and driver performance monitoring, fare collection and video monitoring; rail companies that are building in wayside data capabilities need constant visibility into complex systems; industrial corporations like utility companies need to monitor high-value assets.

The Digi WR54 architecture supports these performance requirements with not just the aforementioned LTE-Advanced cellular module, but four Gigabit Ethernet ports for wired systems and the latest 802.11 ac Wi-Fi which combine to support the needs of any user. Other key features include:

  • Dual-core 880 MHz MIPS processor: designed with this high-speed architecture, the Digi WR54 is future-built with a CPU capable of supporting higher network speeds and capabilities as infrastructure is updated to support them
  • SAE J1455, MILSTD-810G and IP-54 rated: tested and certified to withstand water, dust, heat, vibration and other environmental challenges suitable to transportation and many industrial applications
  • Optional dual-cellular radios for continuous connectivity between carriers: for users that cannot afford downtime, if the primary cellular carrier drops out, the Digi WR54 automatically and immediately switches over to the secondary carrier
  • Digi TrustFence: a device-security framework that simplifies the process of securing connected devices and adapts to new and evolving threats
  • Digi Remote Manager: with this Digi web-based management tool, users can simply manage their devices, receive alerts and monitor the health of their deployed devices

For users looking to add high-speed passenger Wi-Fi to mass transit systems, the recently launched Digi WR64 dual LTE-Advanced cellular and dual 802.11ac Wi-Fi router offers an all-in-one mobile communications solution for secure cellular connectivity between vehicles and a central operations center. It offers a flexible interface design with integrated Wi-Fi for client and access point connectivity along with USB, serial, a four-port wired Ethernet switch, GPS and Bluetooth in order to consolidate multiple transit or industrial applications into a single, consolidated router.

Digi International| www.digi.com

Low-Power PMIC Enables High Sensitivity Optical Measurements

Maxim Integrated Products has introduced its latest tiny, highly integrated power-management IC (PMIC). The ultra-low-power MAX20345 integrates a lithium charger and debuts a unique architecture that optimizes the sensitivity of optical measurements for wearable fitness and health applications. In wearables, optical-sensing accuracy is impacted by a variety of biological factors unique to the user. Designers have been striving to increase the sensitivity of optical systems, in particular the signal-to-noise ratio (SNR), to cover a broader spectrum of use cases.
Traditional low-quiescent-current regulators favored in wearable applications come with tradeoffs that degrade SNR on the wrist, such as high-amplitude ripple, low-frequency ripple and long-settling times. Some designers have even turned to high-quiescent-current alternatives to overcome these drawbacks, but they must deal with increased power consumption, which reduces battery runtime or requires a larger battery. According to Maxim, the MAX20345 features a first-of-its-kind buck-boost regulator based on an innovative architecture that’s optimized for highly accurate heart-rate, blood-oxygen (SpO2) and other optical measurements. The regulator delivers the desired low-quiescent current performance without the drawbacks that degrade SNR and, as a result, can increase performance by up to 7dB.

The MAX20345 is also the latest in a line of ultra-low-power PMICs for small wearables and IoT devices that help raise efficiency without sacrificing battery runtime. To meet these needs, the MAX20345 integrates a lithium-ion battery charger; six voltage regulators, each with ultra-low quiescent current; three nanoPower bucks (900 nA typical) and three ultra-low quiescent current LDO regulators (as low as 550 nA typical). Two load switches allow disconnecting of system peripherals to minimize battery drain. Both the buck-boost and the bucks support dynamic voltage scaling (DVS), providing additional power-saving opportunities when lower voltages can be deployed under favorable conditions. The MAX20345 is available in a 56-bump, 0.4mm pitch, 3.37 mm x 3.05 mm wafer-level package (WLP.)

Key Advantages

  • Superior Performance for Optical Systems: the integrated buck-boost regulator provides the low ripple at high frequency that will not interfere with optical measurements. These short settling times support the high-sensitivity optical-sensor measurements on wearables.
  • Extended Battery Life: regulators with nanoPower quiescent current reduce sleep and standby power, which in turn extends battery runtime and allows for smaller battery size. High-efficiency regulators preserve battery energy during active states.
  • Small Footprint: by eliminating multiple discrete components, the MAX20345 provides a sophisticated power architecture for space-constrained wearable and IoT designs.

The MAX20345 is available at Maxim’s website for $4.45 (1000-up, FOB USA) and is also available from authorized distributors. The MAX20345EVKIT# evaluation kit is available for $57.00

Maxim Integrated | www.maximintegrated.com

 

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Suite of Certification of Evidence Rolls for Wind River Cert RTOS

Wind River has announced the release of a full suite of automotive, avionics, and industrial safety certification evidence for the latest version of its VxWorks Cert Edition real-time operating system (RTOS). The RTOS for safety-critical applications is designed and developed to the highest achievable safety levels accepted by worldwide certification authorities.

VxWorks solutions have been used in more than 550 safety certification programs by more than 350 customers across industries. This most recent suite of certification evidence builds on Wind River’s 20-plus years of experience in safety certification software products, and demonstrates the company’s commitment to industry-leading safe, secure, and reliable solutions.

Like the RTOS itself, the commercial off-the-shelf (COTS) evidence is designed for reuse and portability with long-term cost-of-ownership benefits for safety-critical projects, including those specifically targeting compliance to the following standards:

  • Automotive: ISO 26262 Automotive Safety Integrity Level (ASIL) D backed by certificates issued by independently accredited certification authority TÜV SÜD
  • Avionics: DO-178C Design Assurance Level (DAL) A
  • Industrial: IEC 61508 Safety Integrity Level (SIL) 3 backed by certificates issued by independently accredited certification authority TÜV SÜD

In addition to VxWorks Cert Edition, the Wind River safety portfolio includes the VxWorks 653 integrated modular avionics (IMA) platform.

Wind River | www.windriver.com

Nordic Semi’s BLE SoC Selected for Ultra Low Power IoT Module

Nordic Semiconductor has announced that Nanopower has selected Nordic’s nRF52832 Bluetooth Low Energy (Bluetooth LE) System-on-Chip (SoC) to provide the wireless connectivity for its nP-BLE52 module, designed for developers of IoT applications with highly restricted power budgets.

The nP-BLE52 module employs a proprietary power management IC—integrated alongside Nordic’s nRF52832 Wafer-Level Chip Scale Package (WL-CSP) SoC in a System-in-Package (SiP)—which enables it to cut power to the SoC, putting it in sleep mode, before waking it up a pre-set time and in the same state as before it was put to sleep. In doing so the SoC’s power consumption in sleep mode is reduced to 10 nA, making it well suited for IoT applications where battery life is critical by potentially increasing cell lifespan 10x.

In active mode, the nRF52832 SoC runs normally. The SoC has been engineered to minimize power consumption with features such as the 2.4GHz radio’s 5.5mA peak RX/TX currents and a fully-automatic power management system. Once the Nordic SoC has completed its tasks, it instructs the nP-BLE52 to put it to sleep and wake it up again at the pre-set time. The nP-BLE52 then stores the Nordics SoC’s state variables and waits until the nRF52832 SoC needs to be powered up again. On wake-up, the device uploads the previous state variables, allowing the Nordic SoC to be restored to the same operational state as before the power was cut. The SoC’s start-up is much more rapid than if it was activated from a non-powered mode.

The nP-BLE52 module also features a low power MCU which can be set to handle external sensors and actuators when the Nordic chip is switched off. In this state, the module still monitors sensors and buffer readings and can trigger wake-ups if these readings are above predetermined thresholds, while consuming less than 1 uA. The nP-BLE52 also integrates an embedded inertial measurement unit (IMU).

The module’s power management is controlled through a simple API, whereby the user can predetermine the duration of the Nordic SoC’s sleep mode, set the wake-up time and date parameters, and select pins for other on/off triggers.

The module offers IoT developers several advantages, either extending battery life and/or reducing the size of the battery required to power the application thereby reducing the end-product footprint. Longer battery life also reduces or eliminates battery swaps and enables the developer to better adjust for remaining useful battery life as the battery discharges. The module is suitable for any battery-powered device which is not required to be constantly active, for example asset tracking, remote monitoring, beacons, and some smart-home applications.

The nRF52832 WL-CSP SoC measures just 3.0 mm by 3.2mm while offering all the features of the conventionally-packaged chip. The nRF52832 is a powerful multiprotocol SoC ideally suited for Bluetooth LE and 2.4 GHz ultra low-power wireless applications. It combines an 64 MHz, 32-bit Arm Cortex M4F processor with a 2.4 GHz multiprotocol radio (supporting Bluetooth 5, ANT, and proprietary 2.4 GHz RF software) featuring -96dB RX sensitivity, with 512kB Flash memory and 64kB RAM.

The WL-CSP SoC is supplied with Nordic’s S132 SoftDevice, a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications. The S132 SoftDevice features Central, Peripheral, Broadcaster, and Observer Bluetooth LE roles, supports up to twenty connections, and enables concurrent role operation. Nordic’s unique software architecture provides clear separation between the RF protocol software and the developer’s application code, easing product development.

Nordic Semiconductor | www.nordicsemi.com

Infineon and TTTech Team Up for Automated Driving Solution

Infineon Technologies and TTTech Auto have released the second generation of their fully integrated automotive-grade safety solution for automated driving use cases. It is based on Infineon’s AURIX TC397XM microcontroller and TTTech Auto’s MotionWise safety software platform. It delivers full support and scalability for level 2+ solutions up to the advanced levels 4 and 5 of automated driving. It helps embedded systems developers achieve faster time-to-market, improved software integration and validation thus reducing overall cost.

The first generation of Infineon’s AURIX microcontroller and TTTech Auto’s safety software platform MotionWise are integral part of zFAS, Audi’s centerpiece for piloted driving, that premiered in the Audi A8. TTTech Auto optimized its series-proven product MotionWise for the new and even more powerful second generation of Infineon’s AURIX microcontroller called TC397XM. The MotionWise safety software platform and underlying hardware are powerful enough to match the requirements of up to level 5 automated driving functions.

Residing on an ASIL-D safety hardware, the second generation of the solution is optimized for safety-critical applications. It is offering an increased ISO 26262 ASIL-D computing performance capability, a richer set of peripherals and advanced security measures. MotionWise enables fail-operational performance, freedom from interference and safety by design with highest ASIL levels for the whole platform. Each application hosted by MotionWise will run encapsulated from its peers, resulting in a safe environment where applications with different safety and real-time requirements can coexist and interact. This allows for seamless integration of applications.

Both companies gained extensive experience through close collaboration with key automotive industry players in long-term series production projects. As a key-component in more than 25 car models with production start since 2017, the first generation of this solution creates valuable synergies for series production. Several customers have already evaluated the second generation of this software/hardware combination and decided to use it in their ADAS series production programs with start of production in 2019.

Infineon Technologies | www.infineon.com

TTTech Auto | www.tttech-auto.com

 

Super-Junction MOSFETs Target Energy-Saving Power Topologies

STMicroelectronics offers its MDmesh M6 series of 600 V super-junction transistors. They are engineered for high efficiency in medium-power resonant and hard-switching converter topologies. The threshold voltage optimized for soft switching makes the new transistors well suited for LLC resonant converters and boost-PFC converters in energy-conscious applications. MDmesh M6 devices perform efficiently in hard-switching topologies, too, with their capacitance profile enhancing light-load efficiency and gate charge (Qg) as low as 16 nC permitting high switching frequencies.
In addition, ST’s state-of-the-art M6 super-junction technology helps reduce RDS(ON) to as little as 0.036 ohms, unleashing extra efficiency gains and increasing power density in equipment such as battery chargers, power adapters, PC power supplies, LED-lighting drivers, telecom and server power supplies, and solar micro-inverters.

Package options include the space-saving and thermally efficient new leadless TO-LL, as well as popular through-hole and surface-mount packages including DPAK, D2PAK, TO-220, TO-247, and PowerFLAT. The JEDEC-registered TO-LL power-package outline has 30% smaller footprint and 50% lower height than the established D²PAK 7-pin, allowing more compact and space-efficient power converters. With low parasitic inductances, TO-LL also helps minimize electromagnetic interference.

Part of the STPOWER portfolio, the MDmesh M6 series comprises 37 part numbers covering current ratings from 13 A to 72 A and is in production now.

STMicroelectronics | www.st.com

MCUs Serve Up Solutions for Car Infotainment

Dashboard Dazzle

As automotive dashboard displays get more sophisticated, information and entertainment are merging into so-called infotainment systems. The new systems are driving a need for powerful MCU solutions that support the connectivity, computing and interfacing requirements particular to these designs.

(Caption for lead image Figure 1: The Cypress Wi-Fi and Bluetooth combo solution uses Real Simultaneous Dual Band (RSDB) technology so that Apple CarPlay (shown) and Android Auto can operate concurrently without degradation caused by switching back and forth between bands.).

By Jeff Child, Editor-in-Chief

Microcontroller (MCU) vendors have a rich legacy of providing key technologies for nearly every aspect of an automobile’s electronics—everything from the powertrain to the braking system to dashboard displays. In recent years, they’ve taken on a new set of challenges as demands rise for ever more sophisticated “infotainment” systems. Advanced touchscreen, processing, networking, voice recognition and more are parts of these subsystems tasked with providing drivers with information and entertainment suited to today’s demands—demands that must rival or exceed what’s possible in a modern smartphone or tablet. And, as driverless cars inch toward mainstream reality, that hunger for rich infotainment functionality will only increase.

In order to meet those system design needs, MCU vendors are keeping pace with highly integrated chip-level solutions and embedded software tailored specifically to address various aspects of the automotive infotainment challenge. Over the past 12 months, MCU companies have announced products aimed at everything from advanced dashboard graphics to connectivity solutions to security technologies. At the same time, many have announced milestone design wins that illustrate their engagement with this dynamic sub-segment of automotive system development.

Smartphone Support

Exemplifying these trends, in July Cypress Semiconductor announced that Pioneer integrated Cypress’ Wi-Fi and Bluetooth Combo solution into its flagship in-dash navigation AV receiver. The solution enables passengers to display and use their smartphone’s apps on the receiver’s screen via Apple CarPlay (Figure 1–lead image above) or Android Auto, which provide the ability to use smartphone voice recognition to search for information or respond to text messages. The Cypress Wi-Fi and Bluetooth combo solution uses Real Simultaneous Dual Band (RSDB) technology so that Apple CarPlay and Android Auto can operate concurrently without degradation caused by switching back and forth between bands.

The Pioneer AVH-W8400NEX receiver uses Cypress’ CYW89359 combo solution, which includes an advanced coexistence engine that enables optimal performance for dual-band 2.4- and 5-GHz 802.11ac Wi-Fi and dual-mode Bluetooth/Bluetooth Low Energy (BLE) simultaneously for advanced multimedia experiences. The CYW89359’s RSDB architecture enables two unique data streams to run at full throughput simultaneously by integrating two complete Wi-Fi subsystems into a single chip. The CYW89359 is fully automotive qualified with AECQ-100 grade-3 validation and is being designed in by numerous top-tier car OEMs and automotive suppliers as a full in-vehicle connectivity solution, supporting infotainment and telematics applications such as smartphone screen-mirroring, content streaming and Bluetooth voice connectivity in car kits.

In October, Cypress announced another infotainment-related design win with Yazaki North America implementing Cypress’ instrument cluster solution to drive the advanced graphics in Yazaki’s instrument cluster for a leading American car manufacturer. According to Cypress, Yazaki selected the solution based on its unique offering of five chips that combine to drive dual displays and provide instant-on memory performance with automotive-grade, ASIL-B safety compliance. The Cypress solution is based on a Traveo MCU, along with two high-bandwidth HyperBus memories in a multi-chip package (MCP), an analog power management IC (PMIC) for safe electrical operation, and a PSoC MCU for system management support. The Traveo devices in the Yazaki instrument cluster were the industry’s first 3D-capable Arm Cortex-R5 cluster MCUs.

Virtualization Embraced

The complexity of automotive infotainment systems has pushed system developers to embrace advanced operating system approaches such as virtualization. Feeding those needs, last June Renesas Electronics rolled out its “R-Car virtualization support package” designed to enable easier development of hypervisors for the Renesas R-Car automotive system-on-chip (SoC). The R-Car virtualization support package includes, at no charge, both the R-Car hypervisor development guide document and sample software for use as reference in such development for software vendors who develop the embedded hypervisors that are required for integrated cockpits and connected car applications.

A hypervisor is a virtualization operating system (OS) that allows multiple guest OSs— such as Linux, Android and various real-time OSs (RTOS)—to run completely independently on a single chip. Renesas announced the R-Car hypervisor in April of 2017 and the new R-Car virtualization Support Package was developed to help software vendors accelerate their development of R-Car hypervisors.

The company’s third-generation R-Car SoCs were designed assuming that they would be used with a hypervisor. The Arm CPU cores, graphics cores, video/audio IP and other functions include virtualization functions. Originally, for software vendors to make use of these functions, they would have had to understand both the R-Car hardware manuals and the R-Car virtualization functions and start by looking into how to implement a hypervisor. Now, by following development guides in the R-Car virtualization support package, not only can software vendors easily take advantage of these functions, they will be able to take full advantage of the advanced features of R-Car. Also, by providing sample software that can be used as a reference, this package supports rapid development.

Technology partnerships have been playing a key role in automotive infotainment trends. Along just those lines, in September Renesas and OpenSynergy, a supplier of automotive hypervisors, announced that the Renesas’ SoC R-Car H3 and OpenSynergy’s COQOS Hypervisor SDK were adopted on Parrot Faurecia’s automotive safe multi-display cockpit. The latest version of Android is the guest OS of the COQOS Hypervisor, which executes both the instrument cluster functionality, including safety-relevant display elements based on Linux, and the Android-based in-vehicle infotainment (IVI) on a single R-Car H3 SoC chip (Figure 2). The COQOS Hypervisor SDK shares the R-Car H3 GPU with Android and Linux allowing applications to be presented on multiple displays, realizing a powerful and flexible cockpit system.

Figure 2
With Android as the guest OS of the COQOS Hypervisor, it executes both the instrument cluster functionality, including safety-relevant display elements based on Linux, and the Android-based in-vehicle infotainment (IVI) on a single R-Car H3 SoC chip.

According to OpenSynergy’s CEO Stefaan Sonck Thiebaut, the COQOS Hypervisor SDK takes full advantage of the hardware and software virtualization extensions provided by Renesas. The OpenSynergy solution includes key features, such as shared display, which allows several virtual machines to use multiple displays flexibly and safely. The R-Car H3 GPU and video/audio IP incorporates virtualization functions, making virtualization by the hypervisor possible and allowing for multiple OSs to operate independently and safely. OpenSynergy’s COQOS Hypervisor SDK is built around a safe and efficient hypervisor that can run software from multipurpose OSs such as Linux or Android, RTOS and AUTOSAR-compliant software simultaneously on one SoC.

Large Touchscreen Support

As the content provided by automotive infotainment systems gets more sophisticated, so too must the displays and user interface technologies that interact with that content. With that in mind, MCU vendors are offering more advanced touchscreen control solutions. Dashboard screens have unique design challenges. Screens in automobiles need to meet stringent head impact and vibration tests. That means thicker cover lenses that potentially impact the touch interface performance. Meanwhile, as screens get larger, they are also more likely to interfere with other frequencies such as AM radio and car access systems. All of these factors become a major challenge in the design of modern automotive capacitive touch systems.

Along just those lines, Microchip in December announced its maXTouch family of single-chip touchscreen controllers designed to address these issues for screens up to 20 inches in size (Figure 3). The MXT2912TD-A, with nearly 3,000 touch sensing nodes, and MXT2113TD-A, supporting more than 2,000 nodes, bring consumers the touchscreen user experience they expect in vehicles. These new devices build upon Microchip’s existing maXTouch touchscreen technology that is widely adopted by manufacturers worldwide. Microchip’s latest solutions offer superior signal-to-noise capability to address the requirements of thick lenses, even supporting multiple finger touches through thick gloves and in the presence of moisture.

Figure 3
The maXTouch family of single-chip touchscreen controllers is designed for screens up to 20 inches in size, and supports up to 3,000 touch sensing nodes. The devices even support multiple finger touches through thick gloves and in the presence of moisture.

As automakers use screens to replace mechanical switches on the dash for sleeker interior designs, safe and reliable operation becomes even more critical. The MXT2912TD and MXT2113TD devices incorporate self- and sensor-diagnostic functions, which constantly monitor the integrity of the touch system. These smart diagnostic features support the Automotive Safety Integrity Level (ASIL) classification index as defined by the ISO 26262 Functional Safety Specification for Passenger Vehicles.

The new devices feature technology that enables adaptive touch utilizing self-capacitance and mutual-capacitance measurements, so all touches are recognized and false touch detections are avoided. They also feature Microchip’s proprietary new signal shaping technology that significantly lowers emissions to help large touchscreens using maXTouch controllers meet CISPR-25 Level 5 requirements for electromagnetic interference (EMI) in automobiles. The new touch controllers also meet automotive temperature grade 3 (-40°C to +85°C) and grade 2 (-40°C to +105°C) operating ranges and are AEC-Q100 qualified.

3D Gesture Control

Aside from the touchscreen display side of automotive infotainment, Microchip for its part has also put its efforts toward innovations in 3D human interface technology. With that in mind, in July the company announced a new 3D gesture recognition controller that offers the lowest system cost in the automotive industry, providing a durable single-chip solution for advanced automotive HMI designs, according to Microchip. The MGC3140 joins the company’s family of easy-to-use 3D gesture controllers as the first qualified for automotive use (Figure 4).

Figure 4
The MGC3140 3D gesture controller is Microchip’s first qualified for automotive use. It’s suited for a range for applications such as navigating infotainment systems, sun shade operation, interior lighting and more.

Suited for a range for applications that limit driver distraction and add convenience to vehicles, Microchip’s new capacitive technology-based air gesture controller is ideal for navigating infotainment systems, sun shade operation, interior lighting and other applications. The technology also supports the opening of foot-activated rear liftgates and any other features a manufacturer wishes to incorporate with a simple gesture action.

The MGC3140 is Automotive Electronics Council AEC-Q100 qualified with an operating temperature range of -40°C to +125°C, and it meets the strict EMI and electromagnetic compatibility (EMC) requirements of automotive system designs. Each 3D gesture system consists of a sensor that can be constructed from any conductive material, as well as the Microchip gesture controller tuned for each individual application.

While existing solutions such as infrared and time-of-flight technologies can be costly and operate poorly in bright or direct sunlight, the MGC3140 offers reliable sensing in full sunlight and harsh environments. Other solutions on the market also come with physical constraints and require significant infrastructure and space to be integrated in a vehicle. The MGC3140 is compatible with ergonomic interior designs and enables HMI designers to innovate with fewer physical constraints, because the sensor can be any conductive material and hidden from view.

Vehicle Networking

While applicable to areas beyond infotainment, an automobile’s ability to network with the outside world has become ever more important. As critical vehicle powertrain, body, chassis, and infotainment features increasingly become defined by software, securely delivering updates such as fixes and option packs over the air (OTA) enhances cost efficiency and customer convenience. Serving those needs, in October STMicroelectronics released its latest Chorus automotive MCU that provides a gateway/domain-controller solution capable of handling major OTA updates securely.

With three high-performance processor cores, more than 1.2 MB RAM and powerful on-chip peripherals, ST’s new flagship SPC58 H Line joins the Chorus Series of automotive MCUs and can run multiple applications concurrently to allow more flexible and cost-effective vehicle-electronics architectures (Figure 5). Two independent Ethernet ports provide high-speed connectivity between multiple Chorus chips throughout the vehicle and enable responsive in-vehicle diagnostics. Also featuring 16 CAN-FD and 24 LINFlex interfaces, Chorus can act as a gateway for multiple ECUs (electronic control units) and support smart-gateway functionality via the two Ethernet interfaces on-chip.

Figure 5
The SPC58 H Line of MCUs can run multiple applications concurrently to allow more flexible and cost-effective vehicle-electronics architectures. Two independent Ethernet ports provide high-speed connectivity between multiple Chorus chips throughout the vehicle.

To protect connected-car functionalities and allow OTA updates to be applied safely, the new Chorus chip contains a Hardware Security Module (HSM) capable of asymmetric cryptography. Being EVITA Full compliant, it implements industry-leading attack prevention, detection and containment techniques.

Working with its large on-chip 10 MB flash, the SPC58NH92x’s context-swap mechanism allows current application code to run continuously even while an update is downloaded and made ready to be applied later at a safe time. The older software can be retained, giving the option to roll-back to the previous version in an emergency. Hyperbus and eMMC/SDIO high-speed interfaces to off-chip memory are also integrated, enabling further storage expansion if needed.

Single Cable Solution

Today’s automotive infotainment systems comprise mobile services, cross-domain communication and autonomous driving applications as part of in-vehicle networking. As a result, these systems require a more flexible solution for transporting packet, stream and control content. Existing implementations are either costly and cumbersome, or too limited in bandwidth and packet data capabilities to support system updates and internetworking requirements.

To address this need, Microchip Technology in November announced an automotive infotainment networking solution that supports all data types—including audio, video control and Ethernet—over a single cable. Intelligent Network Interface Controller networking (INICnet) technology is a synchronous, scalable solution that significantly simplifies building audio and infotainment systems, offering seamless implementation in vehicles that have Ethernet-oriented system architectures (Figure 6).

Figure 6
INICnet technology is a synchronous, scalable solution that significantly simplifies building audio and infotainment systems, offering seamless implementation in vehicles that have Ethernet-oriented system architectures.

Audio is a key infotainment feature in vehicles, and INICnet technology provides full flexibility through supporting a variety of digital audio formats with multiple sources and sinks. INICnet technology also provides high-speed packet-data communications with support for file transfers, OTA software updates and system diagnostics via standard Ethernet frames. In this way, INICnet technology supports seamless integration of Internet Protocol (IP)-based system management and data communications, along with very efficient transport of stream data. INICnet technology does not require the development and licensing of additional protocols or software stacks, reducing development costs, effort and time.

INICnet technology provides a standardized solution that works with both Unshielded Twisted Pair (UTP) at 50 Mbps and coaxial cable at 150 Mbps. With low and deterministic latency, INICnet technology supports deployment of complex audio and acoustics applications. Integrated network management supports networks ranging from two to 50 nodes, as well as processor-less or slim modules where the node is remotely configured and managed. The solution’s Power over Data Line (PoDL) capability saves costs on power management for microphones and other slim modules. Nodes can be arranged in any order with the same result, and any node in the system can directly communicate with any other node in the system.

Security for Connected Cars

As cars become more network-connected, the issue of security takes on new dimensions. In October, Infineon Technologies announced a key effort in cybersecurity for the connected car by introducing a Trusted Platform Module (TPM) specifically for automotive applications—the first on the market, according to the company. The new OPTIGA TPM 2.0 protects communication between the car manufacturer and the car, which increasingly turns into a computer on wheels. A number of car manufacturers already designed in Infineon’s OPTIGA TPM.

The TPM is a hardware-based security solution that has proven its worth in IT security. By using it, car manufacturers can incorporate sensitive security keys for assigning access rights, authentication and data encryption in the car in a protected way. The TPM can also be updated so that the level of security can be kept up to date throughout the vehicle’s service life.

Cars send real-time traffic information to the cloud or receive updates from the manufacturer “over the air,” for example to update software quickly and in a cost-effective manner. The senders and recipients of that data—whether car makers or individual components in the car—require cryptographic security keys to authenticate themselves. These critical keys are particularly protected against logical and physical attacks in the OPTIGA TPM as if they were in a safe.

Early Phase Critical

Incorporating the first or initial key into the vehicle is a particularly sensitive moment for car makers. When the TPM is used, this step can be carried out in Infineon’s certified production environment. After that, the keys are protected against unauthorized access; there is no need for further special security precautions. The TPM likewise generates, stores and administers further security keys for communication within the vehicle. And it is also used to detect faulty or manipulated software and components in the vehicle and initiate troubleshooting by the manufacturer in such a case.

Figure 7
The SLI 9670 consists of an attack-resistant security chip (shown) and high-performance firmware developed in accordance with the latest security standard. The firmware enables immediate use of security features, such as encryption, decryption, signing and verification.

The SLI 9670 consists of an attack-resistant security chip and high-performance firmware developed in accordance with the latest security standard (Figure 7). The firmware enables immediate use of security features, such as encryption, decryption, signing and verification. The TPM can be integrated quickly and easily in the system thanks to the open source software stack (TSS stack) for the host processor, which is also provided by Infineon. It has an SPI interface, an extended temperature range from -40°C to 105°C and the advanced encryption algorithms RSA-2048, ECC-256 and SHA-256. The new TPM complies with the internationally acknowledged Trusted Computing Group TPM 2.0 standard, is certified for security according to Common Criteria and is qualified in accordance with the automotive standard AEC-Q100.

Side by side with driverless vehicle innovations, there’s no doubt that infotainment systems represent one of the most dynamic subsets of today’s automotive systems design. MCU vendors offer a variety of chip and software solutions addressing all the different pieces of car infotainment requirements from display interfacing to connectivity to security. Circuit Cellar will continue to follow these developments. And later this year, we’ll take a look specifically at MCU solutions aimed at enabling driverless vehicles and assisted driving technologies.

RESOURCES

Cypress Semiconductor | www.cypress.com
Infineon Technologies | www.infineon.com
Microchip | www.microchip.com
OpenSynergy | www.opensynergy.com
Renesas Electronics America | www.renesas.com
STMicroelectronics | www.st.com

Read the February 343 issue of Circuit Cellar

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Tool Revision Adds Arm Cortex-M Trace and Debug Support

Lauterbach has announced a new revision of their debug and trace probes for Cortex-M based devices. As Cortex-M processors are becoming clocked at greater and greater frequencies, the trace port clocks must also increase to keep pace and prevent loss of valuable data. To provide developers with a more future-proof solution to this perpetual cycle of increasing frequency, the new High-Speed Whisker cables are designed to work with trace clock frequencies of up to 200 MHz across trace ports ranging from 1-bit to 4-bits wide, giving a total trace port bandwidth of up to 200 MB/s.
With increased trace clock speeds comes an increased risk of signal misalignment when parallel trace pins are sampled. The High-Speed Whisker cable includes the innovative auto-focus technology that not only detects the trace port clock frequency but can also adjust the optimum sampling points of each pin to negate any alignment issues in the timing of the data signals. The points where each signal contains valid data, or data eyes, for each pin can be displayed in the TRACE32 PowerView software.

Detailed information about jitters, rising and falling edges is also displayed and users are provided with the capability of manually adjusting the sampling point of each signal. Once configured, these sampling points may be saved and recalled for future use of the tools on this target. The High-Speed Whisker cable will start shipping in January 2019 for TRACE32 µTrace and CombiProbe. Customers who purchased these units during 2018 may request a free upgrade.

Lauterbach | www.lauterbach.com

 

 

SIMO PMICs Shrink Power Regulator Size in Half

Six new low-power power-management integrated circuits (PMICs) from Maxim Integrated Products are designed to reduce the power-management footprint by up to 50 percent for space-constrained products such as wearables, hearables, sensors, smart-home automation hubs and internet of things (IoT) devices. They increase the overall system efficiency by nine percent compared to the closest competitive solution, while also reducing heat dissipation, an important consideration for wearable products that make skin contact.
The unique control architecture in the MAX17270 (shown), MAX77278, MAX77640/MAX77641 and MAX77680/MAX77681 PMICs allows a single inductor to serve as the critical energy-storage element for multiple, independent DC-rail outputs. This allows engineers to reduce the number of bulky inductors in their designs, thereby improving efficiency, shrinking form factor and reducing heat dissipation. In addition, the low quiescent current of the PMICs plays an important role in extending battery life. With the intrinsic buck-boost operation of the PMICs, the power rails can operate over a battery’s entire range.

MAX17270: Smallest Size and Lowest Quiescent Current
At 50 percent smaller than previous-generation SIMO-only solutions, the MAX17270 SIMO buck-boost converter provides the industry’s smallest solution size while reducing the number of inductors and ICs that are required for a power tree. Its quiescent current of 850nA for one SIMO channel and 1.3µA for three SIMO channels is the lowest in the market and helps extend battery life of end devices. In addition, the product’s low power consumption prevents overheating and reduces frequent charging cycles for wearables and hearables. They are available in TQFN and WLP package options.

MAX77278: Power Path Charger Optimized for Small Li+ Batteries
This ultra-low-power SIMO PMIC provides three buck-boost regulators with independent voltage outputs (0.8VOUT to 5.25VOUT), 16µA operating quiescent current/300nA standby current and flexible power sequencing. The device is also a charger for small Li+ cells (7.5mA – 300mA CC range). It includes an adjustable 425mA current sink for an LED, eight general-purpose input/output (GPIO) pins and a 3.7125V to 5.3V, 50mA low-noise low-dropout regulator (LDO) with fixed headroom control in a total solution size as low as 24mm2. The PMIC’s I2C interface allows an applications processor to monitor the status and control power management. The MAX77278 is ideal for remote controls, health and fitness monitors, body cameras and IoT applications.

MAX77640/MAX77641: Highly Integrated Battery Charging and Power Solutions
These ultra-low-power SIMO PMICs feature three buck-boost regulators, a low-noise 150mA LDO, a GPIO output port, a triple current sink for an RGB LED array and flexible power sequencing. Operating current is just 5.6µA and shutdown current is 300nA. Available in a 16mm2 total solution size, the MAX77640 and MAX77641 are ideal for applications with a built-in charger in areas like wearables, fitness and health monitoring and IoT.

MAX77680/MAX77681: Mini PMICs for Always-On, Low-Power Applications
These ultra-low-power SIMO PMICs provide three buck-boost regulators, 3.0µA operating quiescent current, 300nA shutdown current and flexible power sequencing. Total solution size is only 15.5mm2. Given their feature set, the MAX77680 and MAX77681 are ideal for more minimalistic platforms that require streamlined resources, such as hearables (Bluetooth headsets/earbuds) and miniaturized IoT devices (rings, watches, e-pens).

The MAX17270 is available for $1.84 (1000-up, FOB USA); the MAX77278 is available for $2.18 (1000-up, FOB USA); the MAX77680 and MAX77681 are available for $1.24 (1000-up, FOB USA); and the MAX77640 and MAX77641 are available for $1.71 (1000-up, FOB USA) at Maxim’s website. The ICs are also available from select authorized distributors.

The MAX17270EVKIT# evaluation kit is available for $100; the MAX77278EVKIT# evaluation kit is available for $100; the MAX77680/MAX77681EVKIT# evaluation kit is available for $100; and the MAX77640/MAX77641EVKIT# is available for $100.

Maxim Integrated | www.maximintegrated.com

Mini-ITX SBC Sports AMD Ryzen APU SoC

WIN Enterprises has announced the MB-73480 which supports the AMD Ryzen Embedded V1000 processor family. The AMD processors combine the performance of the AMD “Zen” CPU and “Vega” GPU architectures in an integrated SoC solution. In addition, the AMD Ryzen processors deliver discrete-GPU caliber graphics and multimedia processing. Compute performance clocks to 3.61 TFLOPS with thermal design power (TDP) as low as 12 W and as high as 54 W.

The advanced AMD Ryzen CPUs and its other features make the MB-73480 well suited for applications requiring high performance graphics and advanced processing power. Applications include: gaming machines, digital signage, medical imaging, industrial control/automation, thin client, office automation and communication infrastructure. WIN Enterprises will customize the PL-81280 based on a customer’s more specific market needs.

MB-73480 Features:

  • AMD embedded components ensure long product life
  • AMD V1000 Socket FP5 BGA Type CPU mounted onboard (Zen Core-4/8 cores with 2 MB L2 Cache) drawing up to 54 W
  • Supports 4x Independent Displays with 4x DP++ Output
  • AMD Radeon™ Vega core, up to 11 Compute Units
  • Dual DDR4 SO-DIMM Socket and supports from DDR4 1333~3200 SO-DIMM (ECC or non-ECC)
  • 2x RJ45 Port with 10/100/1000 Mbps Transfer speed (Intel I211AT)
  • 5x USB 3.0, 1x USB 2.0, 5x COM, 1x CFast Card, 1x M.2 2280 Socket (B+M key),1x Audio-Jack
  • 2x SATA III Ports with 5 V Power; supports 2x 8G UMLC SATA DOM
  • TPM 2.0
  • 0°C to +60°C operating temperature

WIN Enterprises | www.win-ent.com

 

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ICs for Consumer Electronics (1/28)  Today’;s consumer electronic product designs demand ICs that enable low-power, high-functionality and cutthroat costs. Today’;s microcontroller, analog IC and power chip vendors are laser-focused on this lucrative, high-stakes market. This newsletter looks at the latest technology trends and product developments in for consumer electronics ICs.

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Building a Generator Control System

Three-Phase Power

Three-phase electrical power is a critical technology for heavy machinery. Learn how these two US Coast Guard Academy students built a physical generator set model capable of producing three-phase electricity. The article steps through the power sensors, master controller and DC-DC conversion design choices they faced with this project.
(Caption for lead image: From left to right: Aaron Dahlen, Caleb Stewart, Kent Altobelli and Christopher Gosvener.).

By Kent Altobelli and Caleb Stewart

Three-phase electrical power is typically used by heavy machinery due to its constant power transfer, and is used on board US Coast Guard cutters to power shipboard systems while at sea. In most applications, electrical power is generated by using a prime mover such as a diesel engine, steam turbine or water turbine to drive the shaft of a synchronous generator mechanically. The generator converts mechanical power to electrical power by using a field coil (electromagnet) on its spinning rotor to induce a changing current in its stationary stator coils. The flow of electrons in the stator coils is then distributed by conductors to energize various systems, such as lights, computers or pumps. If more electrical power is required by the facility, more mechanical power is needed to drive the generator, so more fuel, steam or water is fed to the prime mover. Together, the prime mover and the generator are referred to as a generator set “genset”.

Because the load expects a specific voltage and frequency for normal operation, the genset must regulate its output using a combination of its throttle setting and rotor field strength. When a real load, such as a light bulb, is switched on, it consumes more real power from the electrical distribution bus, and the load physically slows down the genset, reducing the output frequency and voltage. The shaft rotational speed determines the number of times per second the rotor’s magnetic field sweeps past the stator coils, and determines the frequency of the sinusoidal output. Increasing the throttle returns the frequency and voltage to their setpoints.

When a partially reactive load—for example, an induction motor—is switched on, it consumes real power, but also adds a complex component called “reactive power.” This causes a voltage change due to the way a generator produces the demanded phase offset between supplied voltage and current. An inductive load, common in industrial settings, causes the voltage output to sag, whereas a capacitive load causes the voltage to rise. Voltage induced in the stator is controlled by changing the strength of the rotor’s electromagnetic field that sweeps past the stator coils in accordance with Faraday’s Law of inductance. Increasing the voltage supply to the rotor’s electromagnet increases the magnetic field and brings the voltage back up to its setpoint.

The objective of our project was to build a physical generator set model capable of producing three-phase electricity, and maintain each “Y”-connected phase at an output voltage of 120 ±5 V RMS (AC) and frequency of 60 ±0.5 Hz. When the load on the system changes, provided the system is not pushed beyond its operating limits, the control system should be capable of returning the output to the acceptable voltage and frequency ranges within 3 seconds. When controlling multiple gensets paralleled in island operation, the distributed system should be able to meet the same voltage and frequency requirements, while simultaneously balancing the real and reactive power from all online gensets.

Two Configurations

Gensets supply power in two conceptually different configurations: “island” operation with stand-alone or paralleled (electrically connected) gensets, or gensets paralleled to an “infinite” bus.” In island operation, the entire electrical bus is relatively small—either one genset or a small number of total gensets—so any changes made by one genset directly affects the voltage and frequency of the electrical bus. When paralleled to an infinite bus such as the power grid, the bus is too powerful for a single genset to change the voltage or frequency. Coast Guard cutters use gensets in island operation, so that is the focus of this article.

When in island operation, deciding how much to compensate for a voltage or frequency change is accomplished using either droop or isochronous (iso) control. Droop control uses a proportional response to reduce error between the genset output and the desired setpoint. For example, if the frequency of the output drops, then the throttle of the prime mover is opened correspondingly to generate more power and raise the frequency back up. Since a proportional response cannot ever achieve the setpoint when loaded (a certain amount of constant error is required to keep the throttle open), the output frequency tends to decrease linearly with an increase in power output. A no-load to full-load droop of 2.4 Hz is typical for a generator in the United States, but this can usually be adjusted by the user.

Frequency control typically uses a mechanical governor to provide the proportional throttle response to meet real power demand. Voltage control typically uses an automatic voltage regulator (AVR) to manipulate the field coil strength to meet reactive power demand. Isochronous mode is more challenging, because it always works to return the genset output to the setpoint. Maintaining zero error on the output usually requires some combination of a proportional response to compensate for load fluctuation quickly, and also a long-term fine-tuning compensation to ensure the steady-state output achieves the setpoint.

If two or more gensets are paralleled, the combined load is supplied by the combined power output of the gensets. As before, maintaining the expected operating voltage and frequency is the first priority, but with multiple gensets, careful changes to the throttle and field can also redistribute the real and reactive power to meet real and reactive power demand efficiently.

If the average throttle or field setting is increased, then the overall bus frequency or voltage, respectively, also increases. If the average throttle or field setting stays the same while two gensets adjust their settings in opposite directions, the frequency or voltage stay the same, but the genset that increased their throttle or field provides a greater portion of the real or reactive power. Redistribution is important because it allows gensets to produce real power at peak efficiency and share reactive power evenly, because excessive reactive power generation derates the generator. Reactive currents flowing through the windings cause heat without producing real, useful power.

Four Conditions

Before the breaker can be closed to parallel generators, four conditions need to be met between the oncoming generators and the bus to ensure smooth load transfer:

1) The oncoming generator should have the same or a slightly higher voltage than the bus.
2) The oncoming generator should have the same or a slightly higher frequency than the bus.
3) The phase angles need to match. For example, the oncoming generator “A” phase needs to be at 0 degrees when the bus “A” phase is at 0 degrees.
4) The phase sequences need to be the same. For example, A-B-C for the oncoming generator needs to match the A-B-C phase sequence of the bus.

Meeting these conditions can be visualized using Figure 1, which shows a time vs. voltage representation of an arbitrary, balanced three-phase signal. The bus and the generator each have their own corresponding plots resembling Figure 1, and the two should only be electrically connected if both plots line up and therefore satisfy the four conditions listed above.

Figure 1
Arbitrary three phase sinusoid

If done properly, closing the breaker will be anticlimactic, and the gensets will happily find a new equilibrium. The gensets should be adjusted immediately to ensure the load is split evenly between gensets. If there is an electrical mismatch, the generator will instantly attempt to align its electrical phase with the bus, bringing the prime mover along for a wild ride and potentially causing physical damage—in addition to making a loud BANG! Idaho National Laboratories demonstrated the physical damage caused by electrical mismatch in its 2007 Aurora Generator Test.

Three primary setups for parallel genset operation are discussed here: droop-droop, isochronous-droop, and isochronous-isochronous. The simplest mode of parallel operation between two or more gensets is a droop-droop mode, where both gensets are in droop mode and collectively find a new equilibrium frequency and voltage according to the real and reactive power demands of the load.

Isochronous-droop (iso-droop) mode is slightly more complex, where one genset is in droop mode and the other is in iso mode. The iso genset always provides the power required to maintain a specific voltage and frequency, and the droop genset produces a constant real power corresponding to that one point on its droop curve. Because the iso genset works more or less depending on the load, it is also termed the “swing” generator.

Finally, isochronous-isochronous (iso-iso) is the most complex. In iso-iso mode, both gensets attempt to maintain the specified output voltage and frequency. While this sounds ideal, this mode has the potential for instability during transient loading, because individual genset control systems may not be able to differentiate between a change in load and a change in the other genset’s power output. Iso-iso mode usually requires direct communication or a higher level controller to monitor both gensets, so they respond to load changes without fighting each other. With no external communication, one genset could end up supplying the majority of the power to the load while the second genset is idling, seeing no need to contribute because the bus voltage and frequency are spot on! At some point one genset could even resist the other genset, consuming real power and causing the generator to “motor” the prime mover. Unchecked, this condition will damage prime movers, so a reverse power relay is usually in place to trip the genset offline, leaving only one genset to supply the entire load.

System Design

Each genset simulated on the Hampden Training Bench had a custom sensor monitoring the generator voltage, current, and frequency output, a small computer running control calculations and a pair of DC-to-DC converters to close the control loop on the generator’s rotational velocity and field strength. The genset was simulated by coupling a 330 W brushed DC motor acting as the prime mover to a four-pole 330 W synchronous generator (Figure 2).

Figure 2
Simulated genset on the Hampden Training Bench

Our power sensor was a custom-designed circuit board with an 8-bit microcontroller (MCU) employed to sample the genset output continuously and provide RMS voltage, RMS current, real power, reactive power, and frequency upon request. The control system ran on a Linux computer with custom software designed to poll the sensor for data, calculate the appropriate control response to return the system to the set point and generate corresponding pulse width modulated (PWM) outputs. Finally, the PWM outputs controlled the DC-to-DC converter to step down the DC supply voltage to drive the prime mover and energize the generator field coil. The component relationships are shown in Figure 3, where the diesel engine in a typical genset was replaced by our DC motor.

Figure 3
Genset component layout

Since this project was a continuation of a previous year of work by Elise Sako and Jasper Campbell, several lessons were learned that required the system be redesigned from the ground up. One of the largest design constraint from the previous year was the decision to use a variable frequency drive (VFD) to drive an induction motor as the prime mover. While this solution is acceptable, it introduces inherent delay in the control loop, because the VFD is designed to execute commands as smoothly but not necessarily as quickly as possible.

Another design constraint was the decision to power the generator field coil using DC regulated by an off-the-shelf silicon controller rectifier (SCR) chopper. Again, while this is an acceptable solution, the system output suffered from the SCR’s slow response time (refresh rate is limited to the AC supply frequency), and voltage output regulation was non-ideal (capacitor voltage refresh again limited by the frequency of the AC supply).

To solve these performance constraints, we selected the responsive and easily controllable DC motor as the prime mover so the DC output from our Hampden Training Bench could be used as the power supply for both the DC motor and the generator field coil. By greatly simplifying the electrical control of the genset, we reduced implementation cost and improved control system response time. …

Read the full article in the February 343 issue of Circuit Cellar
(Full article word count: 6116 words; Figure count: 14 Figures.)

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