New CPU Core Boosts Performance for Renesas MCUs

Renesas Electronics has announced the development of its third-generation 32-bit RX CPU core, the RXv3. The RXv3 CPU core will be employed in Renesas’ new RX microcontroller families that begin rolling out at the end of 2018. The new MCUs are designed to address the real-time performance and enhanced stability required by motor control and industrial applications in next-generation smart factory, smart home and smart infrastructure equipment.

The RXv3 core boosts CPU core architecture performance with up to 5.8 CoreMark/MHz, as measured by EEMBC benchmarks, to deliver industry-leading performance, power efficiency and responsiveness. The RXv3 core is backwards compatible with the RXv2 and RXv1 CPU cores in Renesas’ current 32-bit RX MCU families. Binary compatibility using the same CPU core instruction sets ensures that applications written for the previous-generation RXv2 and RXv1 cores carry forward to the RXv3-based MCUs. Designers working with RXv3-based MCUs can also take advantage of the robust Renesas RX development ecosystem to develop their embedded systems.
The RX CPU core combines a design optimized for power efficiency and a fabrication process producing excellent performance. The new RXv3 CPU core is primarily a CISC (Complex Instruction Set Computer) architecture that offers significant advantages over the RISC (Reduced Instruction Set Computer) architecture in terms of code density. RXv3 utilizes a pipeline to deliver high instructions per cycle (IPC) performance comparable to RISC. The new RXv3 core builds on the proven RXv2 architecture with an enhanced pipeline, options for register bank save functions and double precision floating-point unit (FPU) capabilities to achieve high computing performance, along with power and code efficiency.

The enhanced RX core five-stage superscalar architecture enables the pipeline to execute more instructions simultaneously while maintaining excellent power efficiency. The RXv3 core will enable the first new RX600 MCUs to achieve 44.8 CoreMark/mA with an energy-saving cache design that reduces both access time and power consumption during on-chip flash memory reads, such as instruction fetch.

The RXv3 core achieves significantly faster interrupt response times with a new option for single-cycle register saves. Using dedicated instruction and a save register bank with up to 256 banks, designers can minimize the interrupt handling overhead required for embedded systems operating in real-time applications such as motor control. RTOS context switch time is up to 20 percent faster with the register bank save function.

The model-based development (MBD) approach has penetrated various application developments; it enables the DP-FPU to help reduce the effort of porting high precision control models to the MCU. Similar to the RXv2 core, the RXv3 core performs DSP/FPU operations and memory accesses simultaneously to substantially boost signal processing capabilities.

Renesas plans to start sampling shipments of RXv3-based MCUs before the end of Q4 2018.

Renesas Electronics |

600-V GaN FET Power Stages Support up to 10 kW

Texas Instruments (TI) has announced a new portfolio of ready-to-use, 600-V gallium nitride (GaN), 50-mΩ and 70-mΩ power stages to support applications up to 10 kW. The LMG341x family enables designers to create smaller, more efficient and higher-performing designs compared to silicon field-effect transistors (FETs) in AC/DC power supplies, robotics, renewable energy, grid infrastructure, telecom and personal electronics applications.
TI’s family of GaN FET devices provides a alternative to traditional cascade and stand-alone GaN FETs by integrating unique functional and protection features to simplify design, enable greater system reliability and optimize the performance of high-voltage power supplies.

Dubbed the LMG3410R050, LMG3410R070 and LMG3411R070 TI’s integrated GaN power stage doubles power density and reduces losses by 80 percent compared to silicon metal-oxide semiconductor field-effect transistors (MOSFETs). Each device is capable of fast, 1-MHz switching frequencies and slew rates of up to 100 V/ns. The portfolio is backed by 20 million hours of device reliability testing, including accelerated and in-application hard switch testing. Additionally, each device provides integrated thermal and high-speed, 100-ns overcurrent protection against shoot-through and short-circuit conditions.

Devices for every power level: Each device in the portfolio offers a GaN FET, driver and protection features at 50 mΩ or 70 mΩ to provide a single-chip solution for applications ranging from sub-100 W to 10 kW.

These devices are available now in the TI store in 8-mm-by-8-mm split-pad, quad flat no-lead (QFN) packaging. The LMG3410R050, LMG3410R070 and LMG3411R070 are priced at US$18.69, $16.45 and $16.45, respectively, in 1,000-unit quantities.

Texas Instruments |

New IDE Version Shrinks Arm MCU Executable Program Sizes

After a successful beta period, Segger Microcontroller has added the new Linker and Link-Time Optimization (LTO) to the latest release build of their powerful cross-platform integrated development environments, Embedded Studio for ARM and Embedded Studio for Cortex-M.

The new product versions deliver on the promise of program size reduction, achieving a significant 5-12% reduction over the previous versions on typical applications, and even higher gains compared to conventional GCC tool chains. These savings are the result of the new LTO, combined with Segger’s Linker and Run-time library emLib-C. Through LTO, it is possible to optimize the entire application, opening the door for optimization opportunities that are simply not available to the compiler.

The Linker adds features such as compression of initialized data and deduplication, as well as the flexibility of dealing with fragmented memory maps that embedded developers have to cope with. Like all Segger software, it is written from scratch for use in deeply embedded computing systems. Additionally, the size required by the included runtime library is significantly lower than that of runtime libraries used by most GCC tool chains.

Segger Microcontroller |

Next Newsletter: Embedded Boards

Coming to your inbox tomorrow: Circuit Cellar’s Embedded Boards newsletter. Tomorrow’s newsletter content focuses on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your
Embedded Boards newsletter issue tomorrow.

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Don’t be left out! Sign up now:

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Analog & Power. (12/4) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (12/11) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

IoT Technology Focus. (12/18) Covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

DC-DC Modules Boast Wide Voltage Range, Small Footprint

Maxim Integrated Products has announced four new micro-system-level IC (“uSLIC”) modules. The MAXM17552, MAXM15064, MAXM17900 and MAXM17903 step-down DC-DC power modules join Maxim’s extensive portfolio of Himalaya power solutions, providing the widest input voltage range (4 V to 60 V) with the smallest solution sizes.

While miniaturization remains the trend for an array of system designs, many of these designs also require a wide range of input voltages. For example, supply voltages in factory automation equipment are susceptible to large fluctuations due to long transmission lines. USB-C and broad 12 V nominal applications require up to 24 V of working voltage protection against transients due to hot plugging of supplies and/or batteries.
The newest Himalaya uSLIC power modules extend the portfolio’s range up to 60 V versus the previous maximum of 42V and come in a solution size (2.6 mm x 3.0 mm x 1.5 mm) less than half the size of the closest competitive offering. The modules feature a synchronous wide-input Himalaya buck regulator with built-in FETs, compensation and other functions with an integrated shielded inductor. Having the inductor in the module simplifies the toughest aspect of power supply design, enabling designers to create a robust, reliable power supply in less than a day.

The newest uSLIC modules are:

• MAXM17552, a 4 to 60V, 100mA module with 100 to 900kHz adjustable switching frequency, 82% efficiency (24V VIN at 5V/0.1A) and external clock synchronization in a 2.6mm x 3mm x 1.5mm package
• MAXM15064, a 4.5 to 60V, 300mA module with 500kHz fixed frequency, 82% efficiency (24V VIN at 5V/0.1A) and built-in output voltage monitoring in a 2.6mm x 3mm x 1.5mm package
• MAXM17900, a 4 to 24V, 100mA module with 100 to 900kHz adjustable switching frequency, 86% efficiency (12V VIN at 5V/100mA), external clock synchronization and built-in output voltage monitoring in a 2.6mm x 3mm x 1.5mm package
• MAXM17903, a 4.5 to 24V, 300mA module with 500kHz fixed switching frequency, 77% efficiency (12V VIN at 3.3V/300mA) and built-in output voltage monitoring in a 2.6mm x 3mm x 1.5mm package

The uSLIC modules can be purchased for the following prices: MAXM17552 for $2.53, MAXM15064 for $2.78, MAXM17900 for $1.39, and MAXM17903 for $1.48 (1000-up, FOB USA); they are also available from authorized distributors. The MAXM17552EVKIT#, MAXM15064EVKIT#, MAXM17900EVKIT# and MAXM17903EVKIT# evaluation kits are available at $29.73 each.

Maxim Integrated |

December (issue #341) Circuit Cellar Article Materials

Click here for the Circuit Cellar article code archive

p.6: IoT Door Security System Uses Wi-Fi: Control Via App or Web, By Norman  Chen, Ram Vellanki and Giacomo Di Liberto

[1] Sharp, “GP2Y0A21YK0F Datasheet,”
[2] Massachusetts Institute of Technology, “Serial to Wi-Fi Tutorial Using ESP8266,”
[3] fuho, “ESP8266 – AT Command Reference,” room-15, March 26, 2015.
[4] Espressif Inc., “ESP8266 AT Command Examples,” 2017.
[5] JetBrains, “Reference,”

Microchip Technology, “PIC32 Peripheral Libraries for MPLAB C32 Compiler,” 2007.

Espressif Systems, “ESPRESSIF SMART CONNECTIVITY PLATFORM: ESP8266,” Oct. 2013. < >

Matthew Ford, “Using ESP8266 GPIO0/GPIO2/GPIO15 pins”, Apr. 2018.
< >

Bill of Materials:

Part Name

Part Number


PIC32 Microcontroller


Microchip Technology

Wi-Fi Module



Distance Sensor



Piezoelectric Speaker



Digital-To-Analog Converter


Microchip Technology

PIC32 Microcontroller
MCP4822 Digital-To-Analog Converter
Microchip Technology |

ESP8266 Wi-Fi Module
Espressif Systems |

GP2Y0A21YK0F Distance Measuring Sensor
Sharp Corporation |

CEP-1141 Piezoelectric Speaker

p.12: FPGAs Provide Edge for Convolutional Neural Networks: Deep Learning Solution, By Ted Marena and Robert Green

[1]  Y. Lecun, L. Bottou, Y. Bengio and P. Haffner: “Gradient-based learning applied to document recognition,” in Proceedings of the IEEE, Vol. 86 No. 11, pp. 2278-2324, Nov 1998.
[2] T. Dettmers: “8-Bit Approximations for Parallelism in Deep Learning,” Computing Research Repository, Vol. abs/1511.04561, 2015.
[3] P. Gysel, M. Motamedi and S. Ghiasi: “Hardware-oriented Approximation of Convolutional Neural Networks,” Computing Research Repository, Vol. abs/1604.03168, 2016.

ASIC Design Services |
Microsemi |

p.20: Designing a Display System for Embedded Use: Noritake Notes,
     By Aubrey Kagan

[1] Hierarchical Menus in Embedded Systems, Circuit Cellar, Issue #160, November 2003
[2] gen4 Display Module Series 7.0” Diablo16 Integrated Display Module datasheet
[3] GT-C9xxP series “General Function” Software Specification (requires registration)  GT800X480A-C903PA Hardware Specification (requires registration)

Cypress Semiconductor |
Noritake |

Links to more of Aubrey’s publications on/in Circuit Cellar, Planet Analog and at are available at:

p.26: Self-Navigating Robots Use BLE: Signals and Servos, By Jane Du and Jacob Glueck

[1] S. Carroll, “PIC32MC250F128B small dev board.”.
[2] L. Jinan Huamao technology Co., “HM-10 Bluetooth breakout module and firmware.”.
[3] Arduino Forums, “How to flash genuine hm-10 firmware on cc2541 (make genuine hm-10 from cc41).”
[4] Cheong, “CCLoader.ino.”.
[5] K. Benoit, “CCLoader.exe.”.
[6] Arduino Forums, “Firmware file for flashing BLE module.”.
[7] L. Jinan Huamao technology Co., “HM-10-2541-v603 firmware.”.
[8] InvenSenses, “MPU-9250 product specification revision 1.1.” 2016.
[9] InvenSenses, “MPU-9250 register map and descriptions revision 1.4.” 2013.
[10] A. K. M. Corporation, “3-axis electronic compass.” 2013.
[11] D. Caulley, N. Nehoran, and S. Zhao, “Self-balancing robot.”.
[12] L. Peneda, A. Azenha, and A. Carvalho, “Trilateration for indoors positioning within the framework of wireless communications,” in 2009 35th annual conference of IEEE industrial electronics, 2009, pp. 2732–2737.

BLE 4.0 Module (TI CC2541) HM-10
Texas Instruments, Inc. |

Continuous Rotation Robotic Servo (FEETECH FS90R)
Pololu |

9-Axis Gyroscope Acceleration Magnetic Sensor (MPU-9250)
TDK InvenSense |

PIC32MX250F128B Microcontroller
Microchip Technology |

p.31: Applying WebRTC to the IoT: Peer-to-Peer Comms, By Allie Mellen

WebRTC’s Github

WebRTC |

Google Developer CodeLabs
HTML5Rocks: Getting Started with WebRTC
BlogGeek.Me Advanced WebRTC Architecture Course

Expert Blogs
WebRTC Hacks
WebRTC by Dr Alex |
WebRTC |

p.36: Chip-Level Solutions Feed AI Needs: Embedded Supercomputing, By Jeff Child

Achronix |
Flex Logix Technologies |
Intel |
Lattice Semiconductor |
Microsemi |
Nvidia |
Quicklogic |
Xilinx |

p.42: Module Solutions Suit Up for IIoT: Compact Connectivity, By Jeff Child

Digi |
Espressif |
Jorjin Technologies |
Rigado |
Telit |
U-blox |

p.46: PRODUCT FOCUS DC-DC Converters: Expanding Options, By Jeff Child

Analog Devices |
Maxim Integrated |
MINMAX Technology |
Murata Power Solutions |
TDK-Lambda Americas |
Vicor |

p.50: EMBEDDED IN THIN SLICES: Internet of Things Security (Part 6):
Identifying Threats, 
By Bob Japenga

[1] OWASP Top 10  – 2017 
[2] CVE-2018-5383
[3] OWASP Internet of Things Top Ten —and  Top 10 IoT Vulnerabilities:   Infographic

Bob’s IoT Checklist Can Be Found Here (updated 11/20/2018)

p.54: THE CONSUMMATE ENGINEER: Real Schematics (Part 1): Passives and Parasitics, By George Novacek

[1] 3-Part articles series: “Transformers 101”, George Novacek, Circuit Cellar issues 302, 303 and 304

The Humble Resistor, George Novacek, Circuit Cellar issues 289

Not So Humble Capacitor, George Novacek, Circuit Cellar issue 291

Inductors, George Novacek, Circuit Cellar issue 292

Electromagnetics Explained by Ron Schmitt, published by Newnes, ISBN 0-7506-7403-2

p.58: THE DARKER SIDE: Do You Speak JTAG?: Up Your Test Game, By Robert Lacoste

JTAGLive controller & Buzz software


Scan test devices with octal buffers

Scan Test Device With Octal D-Type Edge-Triggered Flip-Flops

Ultra-low-power 32-bit Value Line ARM Cortex-M3 MCU

JTAG standards and links to IEEE website

IEEE Std1149.1 (JTAG)Testability
Texas Instruments 1997

JTAG tutorial

Instructions on doing (semi-)manual JTAG boundary scan with OpenOCD
Paul Fertser

Architecting a Multi-Voltage JTAG Chain
Hossain Hajimowlana , Analog Devices

JTAG Technologies |
Microchip Technology |
SEGGER Microcontroller |
STMicroelectronics |
Texas Instruments |

p.65: FROM THE BENCH: Sun Tracking Project: Using PIC18 MCU, By Jeff Bachiochi

Flash Microcontroller with High Performance PWM and A/D
Microchip Technology

Ambient Light Sensor
Everlight America
Toll Free: 844-352-6786

Serial LCD Board
Modern Device

Figure 2:  www.didel.commicrokitencoderEncoder.html

Everlight America |
Modern Device |
Microchip Technology |

p.79: The Future of IIoT Sensors: Rethinking the IIoT Sensor Domain for the Smart Factory, By Justin Moll


Slim Signage Player Features Radeon E8860 GPU and 6 HDMI Ports

By Eric Brown

Ibase’s new SI-626 digital signage and video wall (VW) player combines high-end functionality with a slim 30 mm height—1.5 mm thinner than its AMD Ryzen V1000 based SI-324 player. Like the SI-324, the SI-626 features hardware based EDID remote management with software setting mode to prevent display issues due to cable disconnection or display identification failures.

SI-626 from two angles
(click images to enlarge)
The system is notable for providing AMD’s Radeon E8860 graphics, which can drive six HDMI 1.4b displays. There’s also hardware EDID emulation for remote operation, as well as a “flexible VW display configuration setting.”

Like Ibase’s recent SI-614 and OPS-compatible IOPS-602
players, the SI-626 supports Intel’s 7th Gen “Kaby Lake” Core processors, and like the IOPS-602, it also supports 6th Gen Skylake parts. The system supports 7th and 6th Gen chips with FCBGA1440 sockets and Intel QM170 or HM170 chipsets by way of a “MBD626” mainboard.

SI-626 front view
(click image to enlarge)
The product page notes that the Core CPUs have 35 W TDPs or lower. Yet, the press release notes only one model: the quad-core 2.8 GHz/ 3.5 GHz Core i7-6820EQ from the Skylake family, which has a 45 W TDP. OS support is listed as “Win7 64-bit, Win10 64-bit Enterprise, and Linux Ubuntu 64-bit (Installation).”

The SI-626 can load up to 32GB of DDR4-2133 RAM and offers an M.2 M-Key 2280 slot for storage. There’s also a 2.5-inch SATA bay and an M.2 E-Key 2230 slot, as well as a full-size mini-PCIe slot for WiFi/BT, 4G LTE, and capture cards.

The SI-626 is equipped with 6x HDMI 1.4 ports with independent audio output and “ultra-high resolution” support. You also get 4x USB 3.0 ports, 2x RS-232 serial ports with RJ45 connectors, and dual GbE ports (Realtek RTL8111G). The system is further equipped with an audio jack, watchdog, mounting brackets, and 2x LEDs.

The 290 mm x 222 mm x 29.9 mm, 2.2 kg signage player provides a 0 to 45°C range with 5 grms, 5~500 Hz, random vibration resistance (with SSD). A segregated ventilation system is said to reduce internal dust.

The SI-626 offers a 12 V DC jack with a 150 W power adapter supported with Ibase iControl power management and Observer remote monitoring technologies. These work together to provide automatic power scheduling, power failure detection, and restoration to default state in the event of a system crash. You can even boot up the system “under low ambient conditions,” says Ibase.

Further information

The SI-626 appears to be available now at an undisclosed price with a standard configuration of 16 GB RAM and a 128 GB SSD. More information may be found at Ibase’s SI-626 product page.

This article originally appeared on on September 20..

Ibase |

SBC Showcases Qualcomm’s 10 nm, Octa-core QCS605 IoT SoC

By Eric Brown

In April, Qualcomm announced its QCS605 SoC, calling it “the first 10nm FinFET fabricated SoC purpose built for the Internet of Things.” The octa-core Arm SoC is available in an Intrinsyc Open-Q 605 SBC with full development kit with a 12V power supply is open for pre-orders at $429. The products will ship in early December.

Open-Q 605, front and back
(click images to enlarge)
The fact that Qualcomm is billing the high-end QCS605 as an IoT SoC reveals how demand for vision and AI processing on the edge is broadening the IoT definition to encompass a much higher range of embedded technology. The IoT focus is also reinforced by the lack of the usual Snapdragon branding. The QCS605 is accompanied by the Qualcomm Vision Intelligence Platform, a set of mostly software components that includes the Qualcomm Neural Processing SDK and camera processing software, as well as the company’s 802.11ac WiFi and Bluetooth connectivity and security technologies.

The QCS605 can run Linux or Android, but Intrinsyc supports its Open-Q 605 board only with Android 8.1.

Intrinsyc also recently launched an Open-Q 624A Development Kit based on a new Open-Q 624A SOM (see farther below).

Qualcomm QCS605 and Vision Intelligence Platform

The QCS605 SoC features 8x Kryo 300 CPU cores, two of which are 2.5GHz “gold” cores that are equivalent to Cortex-A75. The other six are 1.7GHz “silver” cores like the Cortex-A55 — Arm’s more powerful follow-on to Cortex-A53.

The QCS605 also integrates an Adreno 615 GPU, a Hexagon 685 DSP with Hexagon vector extensions (“HVX”), and a Spectra 270 ISP that supports dual 16-megapixel image sensors. Qualcomm also sells a QCS603 model that is identical except that it offers only 2x of the 1.7GHz “Silver” cores instead of six.

Qualcomm sells the QCS605 as part of a Vision Intelligence Platform — a combination of software and hardware starting with a Qualcomm AI Engine built around the Qualcomm Snapdragon Neural Processing Engine (NPE) software framework. The NPE provides analysis, optimization, and debugging tools for developing with Tensorflow, Caffe, and Caffe2 frameworks. The AI Engine also includes the Open Neural Network Exchange interchange format, the Android Neural Networks API, and the Qualcomm Hexagon Neural Network library, which together enable the porting of trained networks.

The Vision Intelligence Platform running on the QCS605 delivers up to 2.1 TOPS (trillion operations per second) of compute performance for deep neural network inferences, claims Qualcomm. The platform also supports up to 4K60 resolution or 5.7K at 30fps and supports multiple concurrent video streams at lower resolutions.

Other features include “staggered” HDR to prevent ghost effects in high-dynamic range video. You also get advanced electronic image stabilization, de-warp, de-noise, chromatic aberration correction, and motion compensated temporal filters in hardware.

Inside the Open-Q 605 SBC

Along with the Snapdragon 600 based Open-Q 600, the Open-Q 605 is the only Open-Q development board that Intrinsyc refers to as an SBC. Most Open-Q kits are compute modules or sandwich-style carrier board starter kits based on Intrinsyc modules equipped with Snapdragon SoCs, such as the recent, Snapdragon 670 based Open-Q 670 HDK.

Open-Q 605 
(click image to enlarge)
The 68 x 50mm Open-Q 605 ships with an eMCP package with 4GB LPDDR4x RAM and 32GB eMMC flash, and additional storage is available via a microSD slot. Networking depends on the 802.11ac (WiFi 5) and Bluetooth 5.x radios. There’s also a Qualcomm GNSS receiver for location and 3x U.FL connectors.

The only real-world coastline port is a USB Type-C that supports DisplayPort 1.4 with 4K@30fps support. If you’d rather use the Type-C port for USB or charging a user-supplied Li-Ion battery, you can turn to an HD-ready MIPI DSI interface with touch support. You also get 2x MIPI-CSI for dual cameras, as well as 2x analog audio.

The Open-Q 605 has a 76-pin expansion header for other interfaces, including an I2S/SLIMBus digital audio interface. The board runs on a 5-15V DC input and offers an extended -25 to 60°C operating range.

Specifications listed for the Open-Q 605 SBC include:

  • Processor — Qualcomm QCS605 with Vision Intelligence Platform (2x up to 2.5GHz and 6x up to 1.7GHz Krait 300 cores); Adreno 615 GPU; Hexagon 685 DSP; Spectra 270 ISP; Qualcomm AI Engine and other VIP components
  • Memory/storage — 4GB LPDDR4X and 32GB eMMC flash in combo eMCP package; microSD slot.
  • Wireless:
    • 802.11b/g/n/ac 2×2 dual-band WiFi (Qualcomm WCN3990) with planned FCC/IC/CE certification
    • Bluetooth 5.x
    • Qualcomm GNSS (SDR660G) receiver with Qualcomm Location Suite Gen9 VT
    • U.FL antenna connectors for WiFi, BT, GNSS
  • Media I/O:
    • DisplayPort 1.4 via USB Type-C up to 4K@30 with USB data concurrency (USB and power)
    • MIPI DSI (4-lane) with I2C touch interface on flex cable connector for up to 1080p30
    • 2x MIPI-CSI (4-lane) with micro-camera module connectors
    • 2x analog mic I/Ps, speaker O/P, headset I/O
    • I2S/SLIMBus digital audio interface with 2x DMIC ports (via 76-pin expansion header)
  • Expansion — 76-pin header (multiple SPI, I2C, UART, GPIO, and sensor I/O; digital and analog audio I/O, LED flash O/P, haptic O/P, power output rails
  • Other features — 3x LEDs; 4x mounting holes; optional dev kit with quick start guide, docs, SW updates
  • Operating temperature — -25 to 60°C
  • Power — 5-15V DC jack and support for user-supplied Li-Ion battery with USB Type-C charging; PM670 + PM670L PMIC; 12V supply with dev kit
  • Dimensions — 68 x 50 x 13mm
  • Operating system — Android 8.1 Oreo

Open-Q 624A
Development Kit

Open-Q 624A Development Kit

Back in May, Google preannounced the Open-Q 624A Development Kit as an official Android Things 1.0 development board along with Intrinsyc’s Snapdragon 212 based Open-Q 212A, Innocomm’s i.MX8M based WB10-AT, and a MediaTek MT8516 development platform. Now, Intrinsyc is pitching the Open-Q 624A Development Kit, as well as the Open-Q 624A SOM module it’s based on, as an Android 8.0 platform aimed at the home hub market. There is no longer any mention of Android Things.

The Open-Q 624A SOM offers 2GB RAM, 4GB eMMC, WiFi-ac, BT 4.2, and an octa-core -A53 Qualcomm Snapdragon 624 SoC based on the Snapdragon 625. The kit is equipped with a USB 3.0 Type-C port, 2x USB host ports, micro-USB client and debug ports, MIPI-CSI and MIPI-DSI interfaces, sensor expansion and haptic output, and an optional GPS receiver. You also get extensive audio features, including I2S/SLIMBUS headers.

Available for $595, the sandwich style kit will ship in mid-December. For more details, see our earlier Android Things development board report.

Further information

The Open-Q 605 SBC is available for pre-order in the full Development Kit version, which costs $429 and ships in early December. The SBC will also be sold on its own at an undisclosed price. More information may be found in Intrinsyc’s Open-Q 605 announcement, as well as the product page and shopping page.

This article originally appeared on on November 14.

Intrinsyc |

Transceivers Ease HD Video Upgrades Using Existing Vehicle Cabling

Analog Devices has announced a transceiver series that enables high-definition (HD) video over existing Unshielded Twisted Pair cables and unshielded connectors. This allow OEMs to upgrade easily from standard-definition cameras to HD cameras and provide the superior resolution and image quality required for today’s automotive camera applications. The new ADV7990 and ADV7991 transmitters and ADV7380 and ADV7381 receivers use ADI’s Car Camera Bus (C2B) technology to enable significant savings in weight, bulk, cost and reduce cable-routing constraints when compared to other automotive link solutions.

The C2B transceivers are defined and designed specifically for automotive applications, which means that along with supporting excellent visual quality over the unshielded infrastructure, significant care was also taken with on-chip EMC/EMI mitigation techniques enabling full compliance to the rigorous industry mandates for EMC, EMI, and ESD robustness. The performance of the innovative cable-compensation design supports 30-meter cable runs with multiple in-line connections for resolutions up to 2 megapixels at 30 Hz or 1 megapixel at 60 Hz.

The ADV7990/91 and ADV7380/81 transceivers feature negligible latency along with uncompressed transmission; the bidirectional control channel uses the same cable and thus incurs no additional costs. These devices support a 75-MHz pixel rate (75 MHz Y, 75 MHz C), “frozen frame” detection while the bidirectional control function supports I2C, interrupt/status and general-purpose I/O (GPIO).

Analog Devices |

Signage-Oriented Mini-STX SBC Taps Ryzen V1000

By Eric Brown

Sapphire, which makes AMD-based graphics cards and motherboards, offers a 147.3 mm x 139.7 mm Mini-STX (5×5-inch) form factor SBC that runs Ubuntu 16.04 or Windows on AMD’s new Ryzen Embedded V1000 SoC. AMD’s Ryzen V1000 is highly competitive on CPU performance with the latest Intel Core chips, and the Radeon Vega graphics are superior, enabling four 4K displays to run at once.

(click image to enlarge)
The only other Ryzen V1000 based SBC we’ve seen is Seco’s open-spec, 120 x 120mm Udoo Bolt, which ships to Kickstarter backers in December. Sapphire’s commercial FS-FP5V is available for sale now with shipments beginning later this month, according to the Tom’s Hardware post that alerted us to the product.

The FS-FP5V starts at $325 for a model equipped with the dual-core, quad-thread V1202B version of the Ryzen V1000 with lower-end Vega 3 graphics. The three models with the quad-core, octa-threaded versions of the SoC go for $340, $390, and $450, with ascending clock rates and graphics ranging from Vega 8 to 11.

AMD Ryzen Embedded V1000 models, all of which are available with the FS-FP5V
(click image to enlarge)
Pricing, which does not include RAM or storage, seems to be a bit higher than the Udoo Bolt. The Bolt also adds an Atmega32U4 MCU for Arduino and Grove compatibility but is limited to the two lower-end V1000 SoC models. The Bolt seems more like a general purpose embedded board while the FS-FP5V, which has up to 4x DisplayPorts, is more directly aimed at digital signage and other media-centric applications including electronic gaming, medical imaging, thin clients, and POS terminals.

Unlike the Udoo Bolt, there’s no microSD slot or eMMC. There is however, a SATA III slot with power headers, as well as an M.2 M-key 2280 slot for SATA III or PCIe. A separate M.2 E-key 2242 connection supports PCIe devices including WiFi modules.

FS-FP5V portside views
(click images to enlarge)
It’s unclear if the cited prices include all four DP++ ports, which are listed as “up to 4x.” The board is further equipped with an audio jack, 2x GbE ports, serial and GPIO headers, and 3x USB 2.0 host ports. There’s also a USB 3.1 Type-C port, which does not appear to be used for DP. It’s unclear if it’s used for power.

Bleujour Kubb enclosure for FS-FP5V (left) and upcoming FS-FP5V-based 2×2 display wall from Seneca Data
(click images to enlarge)
This is Sapphire’s first Mini-STX SBC. Its other AMD-based motherboards include AMD R-Series based Mini-ITX boards and some 4×4-inch eNUC form factor boards such as the G-Series based LX 210.

In the YouTube video farther below, a Sapphire rep says his company can make custom boards based on the Ryzen V1000. The video also shows a Kubb enclosure for the FS-FP5V from Bleujour, as well as an upcoming 2×2 digital signage display wall from Seneca Data that taps the FS-FP5V to generate 4x 4K displays.

Specifications listed for the FS-FP5V include:

  • Processor — AMD Ryzen Embedded V1000 (see chart above)
  • Memory — 0GB to 32GB of dual-channel DDR4 RAM up to 3200MHz with ECC support via 2x sockets
  • Storage:
    • M.2 M-Key 2280 slot for SATA III or PCIe x4)
    • SATA III connector with 5V SATA power
  • Wireless — M.2 E-Key 2242 for WiFi and other PCIe x1
  • Networking — 2x Gigabit Ethernet ports (Realtek RTL8111G)
  • Display/media:
    • Up to 4x DisplayPort++ available via 2x dual-role USB 3.0 Type-C ports
    • 4x simultaneous 4K@60 displays
    • Radeon Vega 3, 8, or 11 graphics with DirectX 12, EGL 1.4, IOMMU 2.0, OpenCL 2.1, OpenGL ES 1.1, 2.x, and 3.x (Halti), OpenGL Next (Vulkan), OpenGL 4.6, 10-bit HEVC decoder (H.265), VP9 decoder, up to 10-bit, limited profile 2, Eyefinity
    • 3.5mm audio jack (ALC262 HD 4CH)
  • Other I/O:
    • USB 3.1 Type-C port
    • 3x USB 2.0 host ports
    • RS232/422/485 header
    • GPIO headers
  • Operating temperature — 0 to 50°C
  • Dimensions — 147.3 x 139.7mm
  • Operating system — Ubuntu 16.04 with Linux 4.9 or 4.14.14; Windows 7/8.1/10 etc.


AMD’s promo video for FS-FP5V
Further information

The FS-FP5V is available now starting at $325, with shipments due later this month. More information may be found at Sapphire’s FS-FP5V product page, which links to an order form.

This article originally appeared on on July 9.

Sapphire |

Tuesday’s Newsletter: IoT Tech Focus

Coming to your inbox tomorrow: Circuit Cellar’s IoT Technology Focus newsletter. Tomorrow’s newsletter covers what’s happening with Internet-of-Things (IoT) technology–-from devices to gateway networks to cloud architectures. This newsletter tackles news and trends about the products and technologies needed to build IoT implementations and devices.

Bonus: We’ve added Drawings for Free Stuff to our weekly newsletters. Make sure you’ve subscribed to the newsletter so you can participate.

Already a Circuit Cellar Newsletter subscriber? Great!
You’ll get your IoT Technology Focus newsletter issue tomorrow.

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Don’t be left out! Sign up now:

Our weekly Circuit Cellar Newsletter will switch its theme each week, so look for these in upcoming weeks:

Embedded Boards.(11/27) The focus here is on both standard and non-standard embedded computer boards that ease prototyping efforts and let you smoothly scale up to production volumes.

Analog & Power. (12/4) This newsletter content zeros in on the latest developments in analog and power technologies including DC-DC converters, AD-DC converters, power supplies, op amps, batteries and more.

Microcontroller Watch (12/11) This newsletter keeps you up-to-date on latest microcontroller news. In this section, we examine the microcontrollers along with their associated tools and support products.

NanoPi Neo4 SBC Breaks RK3399 Records for Size and Price

By Eric Brown

In August, FriendlyElec introduced the NanoPi M4, which was then the smallest, most affordable Rockchip RK3399 based SBC yet. The company has now eclipsed the Raspberry Pi style, 85 mm x 5 6 mm NanoPi M4 on both counts, with a 60 mm x 45 mm size and $45 promotional price ($50 standard). The similarly open-spec, Linux and Android-ready NanoPi Neo4, however, is not likely to beat the M4 on performance, as it ships with only 1 GB of DDR3-1866 instead of 2 GB or 4 GB of LPDDR3.

NanoPi Neo4 and detail view
(click images to enlarge)

This is the first SBC built around the hexa-core RK3399 that doesn’t offer 2GB RAM at a minimum. That includes the still unpriced Khadas Edge, which will soon launch on Indiegogo, and Vamrs’ $99 and up, 96Boards form factor Rock960, in addition to the many other RK3399 based entries listed in our June catalog of 116 hacker boards.

NanoPi M4

Considering that folks are complaining that the quad -A53, 1.4 GHz Raspberry Pi 3+ is limited to only 1GB, it’s hard to imagine the RK3399 is going to perform up to par with only 1GB. The SoC has a pair of up to 2GHz Cortex-A72 cores and four Cortex -A53 cores clocked to up to 1.5GHz plus a high-end Mali-T864 GPU.

Perhaps size was a determining factor in limiting the board to 1 GB along with price. Indeed, the 60 mm x 45 mm footprint ushers the RK3399 into new space-constrained environments. Still, this is larger than the earlier 40 mm x 40 mm Neo boards or the newer, 52 mm x 40mm NanoPi Neo Plus2, which is based on an Allwinner H5.

We’re not sure why FriendlyElec decided against calling the new SBC the NanoPi Neo 3, but there have been several Neo boards that have shipped since the Neo2, including the NanoPi Neo2-LTS and somewhat Neo-like, 50 x 25.4mm NanoPi Duo.

The NanoPi Neo4 differs from other Neo boards in that it has a coastline video port, in this case an HDMI 2.0a port with support for up to 4K@60Hz video with HDCP 1.4/2.2 and audio out. Another Neo novelty is the 4-lane MIPI-CSI interface for up to a 13-megapixel camera input.

NanoPi Neo4 with and without optional heatsink
(click images to enlarge)
You can boot a variety of Linux and Android distributions from the microSD slot or eMMC socket (add $12 for 16GB eMMC). Thanks to the RK3399, you get native Gigabit Ethernet. There’s also a wireless module with 802.11n (now called Wi-Fi 4) limited to 2.4 GHz Wi-Fi and Bluetooth 4.0.

The NanoPi Neo4 is equipped with coastline USB 3.0 and USB 2.0 host ports plus a Type-C power and OTG port and an onboard USB 2.0 header. The latter is found on one of the two smaller GPIO connectors that augment the usual 40-pin header, which like other RK3399 boards, comes with no claims of Raspberry Pi compatibility. Other highlights include an RTC and -20 to 70℃ support.

Specifications listed for the NanoPi Neo4 include:

  • Processor — Rockchip RK3399 (2x Cortex-A72 at up to 2.0 GHz, 4x Cortex-A53 at up to 1.5 GHz); Mali-T864 GPU
  • Memory:
    • 1GB DDR3-1866 RAM
    • eMMC socket with optional ($12) 16GB eMMC
    • MicroSD slot for up to 128GB
  • Wireless — 802.11n (2.4GHz) with Bluetooth 4.0; ext. antenna
  • Networking — Gigabit Ethernet port
  • Media:
    • HDMI 2.0a port (with audio and HDCP 1.4/2.2) for up to 4K at 60 Hz
    • 1x 4-lane MIPI-CSI (up to 13MP);
  • Other I/O:
    • USB 3.0 host port
    • USB 2.0 Type-C port (USB 2.0 OTG or power input)
    • USB 2.0 host port
  • Expansion:
    • GPIO 1: 40-pin header — 3x 3V/1.8V I2C, 3V UART, SPDIF_TX, up to 8x 3V GPIOs, PCIe x2, PWM, PowerKey
    • GPIO 2: 1.8V 8-ch. I2S
    • GPIO 3: Debug UART, USB 2.0
  • Other features — RTC; 2x LEDs; optional $6 heatsink, LCD, and cameras
  • Power — DC 5V/3A input or USB Type-C; optional $9 adapter
  • Operating temperature — -20 to 70℃
  • Dimensions — 60 x 45mm; 8-layer PCB
  • Weight – 30.25 g
  • Operating system — Linux 4.4 LTS with U-boot 2014.10; Android 7.1.2 or 8.1 (requires eMMC module); Lubuntu 16.04 (32-bit); FriendlyCore 18.04 (64-bit), FriendlyDesktop 18.04 (64-bit); Armbian via third party;

Further information

The NanoPi Neo4 is available for a promotional price of $45 (regularly $50) plus shipping, which ranges from $16 to $20. More information may be found on FriendlyElec’s NanoPi Neo4 product page and wiki, which includes schematics, CAD files, and OS download links.

This article originally appeared on on October 9.

FriendlyElec |

What are the 5 Biggest Myths About Developing Embedded Vision Solutions?

Are embedded vision solutions complex? Expensive? Strictly about software? Get answers to your top questions about developing embedded vision solutions, right from Avnet & Xilinx.

We’re at the moment of truth with embedded vision systems as scores of new applications means designs must go up faster than ever—with new technologies dropping every day.

But isn’t embedded vision complex? Lacking scalability? Rigid in its design capability?

Truth be told, most of those ideas are myths. From the development of the first commercially viable FPGA in the 1980s to now, the amount of progress that’s been made has revolutionized the space.

So while it can be complex to decide how you’ll enter an ever-changing embedded vision market, it’s simpler than it used to be. It’s true: Real-time object detection used to be a strictly research enterprise and image processing a solely software play. Today, though, All Programmable devices enable system architects to create embedded vision solutions in record time.

As far as flexibility goes, you’ll find something quite similar. In the past, programming happened on the software side because hardware was preformatted. But FPGAs are more customizable. They contain logic blocks, the programmable components and reconfigurable interconnects that allow the chip to be programmed which allows for more efficiency of power, temperature and design—all without the need of an additional OS.

Ready to bust some more myths around embedded vision? Watch our video breaking down the five biggest myths around embedded vision development.


Wireless Charging

Electric Field of Dreams

The concept of wireless charging can be traced all the way back to Nikola Tesla. Here, Jeff examines the background and principles involved in charging devices today without wires, and takes a hands-on dive into the technology.

By Jeff Bachiochi


Nikola Tesla is the recognized inventor of the brushless AC induction motor, radio, fluorescent lighting, the capacitor discharge ignition system for automobile engines and more. His AC power (with Westinghouse) beat out Thomas Edison’s DC power in the bid for the electrification of America. DC transmission is limited to miles due to its relatively low voltage and its transmission line loses. Thanks to the advent of the transformer, AC can be manipulated allowing higher voltages and higher efficiency power transmission. Today’s research in superconducting cable may be challenging these concepts—but that’s a story for another time.

Tesla wanted to provide a method of broadcasting electrical energy without wires. The Wardenclyffe Tower Facility on Long Island Sound was to be used for broadcasting both wireless communications and the transmission of wireless power. Tesla even viewed his research on power transmission as more important than its use as a method for communications. Unfortunately, Nikola was never able to make his vision a reality.
We think of Guglielmo Marconi as being the father of radio for his development of Marconi’s law and a radio telegraph system. He was able to obtain a patent for the radio using some of Tesla’s own ideas. It’s interesting to note that after Tesla’s death in 1946, the U.S. Supreme Court invalidated the Marconi patent because the fundamental radio circuit had been anticipated by Tesla. Again, not the direction of this article.
It was likely that Nikola’s work in far-field power transmission had not been fruitful due to propagation losses (inverse square law). Even today’s work on beam-formed, far-field transmissions are marginally successful. Transformers are successful because they operate in the near field. The close proximity between the primary and secondary coil and a well-designed magnetic energy path result in low energy losses in transformers.

Modern Wireless Charging
Today’s wireless charging systems for our portable devices are based on transformer operation. However, the primary and secondary coils are not in physical contact yet still transfer energy Figure 1. Efforts to maximize the magnetic field’s coupling exist, but this less-than-ideal coupling reduces the efficiency of the transfer—50% to 70% efficient. There are basically two methodologies today: inductive (tight) coupling (near field) and resonant inductive (loose) coupling (mid field). The resonant circuit allows an equivalent power to be transferred at a slightly greater distance.

Figure 1
The device is considered near-field (closely coupled) when the distance between the coils is less than the coils diameter. The mid-field device’s distance exceeds the coils diameter and relies on resonance to improve its power transfer.

Wireless efforts are in total flux with at least three organizations jockeying for position: The Wireless Power Consortium (WPC, induction), the Alliance for Wireless Power (A4WP, resonant) and Power Matters Alliance (PMA, induction). Interestingly, after WPC announced its plans to widen their specs to include resonant technologies, A4WP and PMA merged to become the AirFuel Alliance and now cover both technologies as well.

Beyond induction type, the biggest differences between the technologies is in control communication. Control of the charging process requires communications between transmitters and receivers. Induction technology uses in-band modulation of the RF signal to send and receive communications. Resonant induction technology uses Bluetooth for out-of-band communications. This makes the transmitter/receiver pair simpler but adds the complexity of Bluetooth. Since many receiving devices already have Bluetooth, this may be moot.

The Qi Standard
The WPC has coined the term Qi for their standard. If you search the web for wireless charging, this term pops up all over the place. This is not to say the AirFuel’s standard isn’t available—it seems to be a difference in promotional strategies. AirFuel has invested in getting their receivers into devices and their transmitters installed in public places. And while Qi receivers are also going into devices, their transmitters seem to be aimed at the individual. That means easy access to both Qi transmitters and receivers.
You can get the V1.2.2 specifications for the Qi standard from the WPC website. The current version (1.2.3) is available only to members now but should be public shortly. The two documents I received were “Reference Designs” and “Interface Definitions” for Power Class 0 specifications.

Power Class 0 aims to deliver up to 5 W of energy wirelessly via magnetic induction. This is accomplished by applying a fixed RF signal—generally in the 140 kHz range—into an inductive load (transformer primary). This is much like providing motor control using a half or full bridge, with the (transmitting) coil as the load instead of a motor.
Referring back to Figure 1, a receiver uses a similar coil (the transformer secondary). This coil supplies rectification circuitry with the voltage/current needed to power the receiver. The receiver can vary its load, which modulates the burden on the transmitting coil. Back at the transmitter, a change in the primary’s current can indicate when the secondary’s load is in range. Initially the transmitters remain relatively inactive, except for a periodic “ping” to look for a receiver. A normal ping will occur every
500 ms and last about 70 ms (Photo 1). Once in range the receiver gets secondary current and can self-power. During the last 50 ms of a ping, a receiver has a chance to communicate by modulating its load at 2 kHz rate (Photo 2). There are presently 16 messages it can choose to send.

Photo 1
This oscilloscope screenshot shows the “ping” transmissions of a wireless transmitter with no receiver in range.

Photo 2
Here we see a receiver sending a packet by modulating its load during the transmitter’s RF transmission.

Each message has four parts: a preamble, header, message and checksum. The preamble consists of from 11 to 25 “1” wake-up bits. The header is a 1-byte command value. The message length is fixed for each command, presently 1 to 8 bytes. The checksum is a 1-byte sum of the header and message bytes. All bytes in the header, message and checksum have an 11-bit asynchronous format consisting of a start bit (0), data bits (for example Command, LSB first), odd parity bit (OP) and stop bit (1). Each bit is sent using bi-phase encoding. Each bit begins with a state change in sync with its 2 kHz clock. The value of a bit is “0” when its logic states does not change during a 2 kHz clock period. If the state does change within that period, then the bit is a “1”.

The receiver has control over the transmitter. It initiates communication to send information and request power transfer. Back in Photo 2 you can see a Control Error Packet with a Header=0x03 and data=0x00. The signed value of the data indicates any difference between the requested and received current level.

While the receiver is in charge (ha!), the transmitter can acknowledge requests with 1 of 3 responses: ACK (accept), NAK (deny), or ND (invalid). Responses have no packet per se, but are merely a Frequency-shift keying (FSK) modulated pattern of 0s, 1s or alternating 0s and 1s. The receiver can request the depth of the FSK modulation from a list of choices between +/- 30 to 282 ns. The depth is defined as the difference in ns between the 1/Fop (operating frequency) and 1/Fmod (modulation frequency). The format is again bi-phase encoding in sync with the RF frequency. All bits begin with a change in modulation frequency. A “1” bit is indicated by a change in frequency after 256 cycles, while a ‘”0” bit has no change until the beginning of the next bit time. Responses are therefore easy for a receiver to demodulate.

So, communication is AM back-scatter from the receiver and FM on the base RF from the transmitter. The present specification defines three packets that can be sent by a transmitter in addition to the ACK, NAK and ND. These are informational and are formatted like the receiver packets, less the preamble.

System Control
From the transmitters point of view, it has 4 basic states: ping, ID, power transfer and selection. The transmitter is idle while in the ping state. Without some communication from a receiver, the transmitter will never do anything but ping. Once communication begins the receiver attempts to identify itself and become configured, at which point the transmitter can start power transfer. The transmitter will continue monitoring its feedback and change states when necessary. For instance, if communication is lost, it must cancel the power transfer state and begin to ping. The ability to detect foreign objects (FOD) is required for any system that can exceed 5W of power transfer. This parameter adds an additional 3 states to the basic 4 states: negotiation, calibration and renegotiation. When using FOD the negotiation state is required to complete identification, configuration and calibration. Calibration allows the transmitter to fine tune its ability to FOD. During the power transfer state, the receiver may wish to adjust its configuration. As long as no requests violate operational parameters, the power transfer state can continue. Otherwise the selection state will redirect further action. You can see how this works in the state diagram in Figure 2.

Figure 2
This is a general state diagram of the Qi standard for wireless chargers. Note two potential paths based whether or not foreign object detection is supported (required for greater than 5 W).

From the receiver’s point of view, it could be in an unpowered (dead) state prior to entering the transmitter’s field. Once within range, the short ping from a transmitter is sufficient to charge up its capacitive supply and begin its application programming. Its first order of business is to look for a legal ping, so it can properly time its first request 40ms after the beginning of a ping. The first packet is a signal strength measurement, some indication of transmitted energy. This is sufficient for the transmitter to enter the identification and configuration state by extending its RF timing and look for additional packets from the receiver. The receiver must now identify itself—version, manufacturer and whether or not it accepts the FOD extensions. A configuration packet will transfer its requirements as well as the optional packets it should expect. The transmitter digests all this data and will determined, based on the receiver’s ability to accept FOD extensions, whether it will proceed directly to the power transfer state or enter the negotiation state.

Packets must have a minimum of 7 ms silent period between each. The values sent in the configuration packet denote an official power contract between the transmitter and receiver. When the receiver doesn’t accept FOD extensions, it is this contract that the transmitter will abide by once it enters the power transfer state. If FOD extensions are enabled, it enters the negotiation state in an attempt to change the contract and provide higher power. The transmitter’s response lets the receiver know when a request to change a parameter is acceptable. This way both receiver and transmitter agree on the power contract it will use when negotiations are closed.

Once negotiations have ended, the calibration state is entered. The calibration consists of multiple packets containing received power values measured by the receiver while it enables and disables its load (maximum and minimum power requirements). This provides the transmitter with some real use values so it can better determine FOD.
During the power transfer (PT) state, the receiver must send a control error packet every 250 ms that the transmitter uses to determine its operating (PID) parameters. Meanwhile, received power packets are sent every 1,500 ms. Without this feedback, the transmitter will drop out of the PT state. Other packets can affect the PT state as well—most notably an end power packet. This may be due to a full charge or other safety issue and the transmitter drops out of the PT state. At this point a receiver can cease communication and while the transmitter will begin pinging, the receiver can rest indefinitely.

Sense, Configure, Charge
I’ve found that the Qi receivers with micro USB connectors make it easy to add wireless charging to your phone or tablet. One of these fits inside my Motorola phone with only the smallest bump of the connector on the outside. My Amazon Fire is not so lucky. It had to stay on the outside (Photo 3).

Photo 3
Shown on the left, the Amazon Fire required me to add the Qi receiver to the outside. It’s covered with a very large band-aid. On the right, my Motorola phone had room inside. The only clue is the receiver’s minimally obtrusive micro USB connector.

Adafruit has a module available that has no connector and is not enclosed in a skin (Photo 4). You can see in that photo that a receiver requires very few external components. This one uses a Texas Instruments bq51013B, which is less than $4. One advantage to choosing this device is the non-BGA version which is appealing to the DIYer that wants to hand solder the device onto a PCB.

Photo 4
You can see how few components are required on the Adafruit Qi wireless receiver shown here on a wireless transmitter. The voltmeter shows a voltage output of 4.98 V.

I suggest that you use high strand, flexible wires when making connections to this because a stiff wire can cause undue stress on flexible circuitry. I want to use this wireless charge receiver to keep some of my robots charged. To do this, the robot has to ride over the top of a transmitter. The receiver would then recharge the on-board battery or batteries. I’ve chosen to use Li-ion batteries because they have a high power-to-weight ratio. They also have a relatively flat discharge curve. Unfortunately, a single cell 3.7-V Li-ion battery is not sufficient to power most motors. Therefore, multiple cells must be used.

When multiple cells are in series the charging becomes an issue because the cells should be charged using a balanced charger to prevent charge imbalance. Charging cells in series as a group cannot prevent the over/under charging of individual cells. This means one of two approaches: Use a single cell and use a boost power converter to obtain your necessary voltage, or use a more complicated multi-cell, balanced charger with a boost converter between the wireless receiver and the charger’s input.
Upon contemplating the pros and cons of each method, I’ve decided to use a modular approach by treating each battery as a separate entity. The simplest charging IC I could find was STMicroelectronics’ STC4054. This is a TSOT23-5L (5-pin) device that requires only one external component to set the charging rate. This is important because some chargers will allow very high currents and I will be sharing the current for all chargers via one wireless receiver. While these can handle 1 A, if I want to say, charge four Li-ion batteries in series I need to limit each charging circuit to 250 mA (250 X 4 = 1,000) or I run the risk of the wireless receiver becoming overloaded and everything will shut down.

The STC4054 has a charging voltage of 4.2 V using the maximum of whatever current you set by the resistor you choose from the PROG pin to ground using the following formula:

rearranging we get…

A minimum VCC of 4.25 V is sufficient to sustain a complete charge cycle. Here is a breakdown of the whole charge cycle: If the battery voltage is below 2.9 V it will be trickle charged at 1/10 of IBAT. Once it reaches 2.9 V it enters the constant current mode charging at IBAT. Once it reaches 4.2 V it switches to constant voltage mode to prevent over charging. The cycle ends when the current drops to less than 1/10 of IBAT. Should the battery voltage fall below 4.05 V, a charging cycle will begin to maintain the battery capacity to a value higher than 80%.

The STC4054 is thermally protected by reducing the charging current should the temperature approach 120°C. The package leads are the main heat conductors from the die, so sufficient copper areas on the PCB will help with heat radiation. The device will max at 800 mA, but is spec’d to handle 500 mA at 50°C. You can expect stability without additional compensation unless you have long leads to the battery. A 1 µF to 4.7 µF capacitor can be added to the BAT connection if necessary.

The CHRG pin is an open-collector output which can be monitored to indicate when the IC is in the charging state. It will pull down an LED if you wish a visual status indicator. This IC will cost you about $1.50. With no voltage applied to the IC, it will go into a power down mode with a drain of only 17 µA on the battery.

Now this circuit takes care of charging a single battery, and we might have up to four in series. It’s the series part that is the problem because only the first can have a reference to ground. Since the wireless receiver is designed to produce a 5 V output, this is easily connected to the first charging circuit. We could try and get fancy with a boost converter to get a 20 V output to feed the four chargers with their inputs in series, but this has all kinds of bad karma associated with it. Fortunately, there is a rather inexpensive solution: Use isolated DC-DC converter modules. All converter inputs are in parallel on the wireless chargers output. Each of the converters’ outputs can be tied to a separate charging circuit. Since each of the converters’ outputs are isolated from its inputs, there is no reference to ground—the minus output of the wireless receiver). That means they can then be used to charge batteries which are connected in series.

The circuit given in Figure 3 shows four changing circuits—each (potentially) using its own isolated 5 VDC to 5 VDC converter. These are available in 1 W to 3 W SIP-style packages and cost from $3 to $10 each. Modules with high current (greater than 3W) are available, but the package style changes to DIP. Their inputs are in parallel with a connector meant to go to the wireless charging receiver. There are a lot of jumpers used to select how the outputs of each charging circuit are to be connected to output connectors. Each charger can charge one Li-ion battery using a standard two-pin 1S1P (one series cell, one parallel cell) connector. Or you can jumper them in series, which uses the standard connectors for 2S1P, 3S1P and 4S1P (series cells).

Figure 3
This schematic shows four Li-ion cell charging circuits using the STC4054. The input to each IC can come from an optional isolated source when using a DC-DC converter from RECOM. If each of the charging circuits are isolated, they can be applied to separate Li-ion cells in series.

You’ll note that multi cell Li-ion battery packs usually come with two connectors—one for use and one for charging. The charging connector contains a wire to each battery junction to allow cell-balanced charging (Photo 5). Battery packs that feature balanced charging usually contain the JST HX connector for charging. The power contacts are another story. They may be JST HSNG style, Dean’s connector or other specialty types.

Photo 5
There seems to be some standardization on balanced Li-ion cell chargers. They require a common plus 1 wire for each cell so each cell can be monitored and charged independently. This means any battery pack with more than one cell requires separate connectors for charging and discharging.

Small Bots ‘n Bats
You’ll find plenty of the small robot bases using AA batteries with a UNO or some other micro platform as its controller. There is nothing wrong with these inexpensive platforms for educational purposes. With a fresh set of batteries, you will usually have predictable behavior. In rather short order however, things will begin to go loony. The motor load will begin to affect the controller as the battery voltage dips. Even at 6 V, with a low drop out regulator, the controller operation and any sensors will quickly become unpredictable. This can be truly a frustrating time for the newbie, as one searches their code for a logic error that might produce the inappropriate action observed, when actually there may be nothing wrong!

You can save a lot of heartache if you just add an extra battery (or two) to raise the voltage to 7.5 V or even better 9 V. I’ve seen kids quickly lose interest or give up entirely simply because they don’t understand what’s happening. I’ve found a better solution is to replace the AAs with a couple of Li-ion 18650 type 3.7 V cells. The 18650 looks like an over-sized AA battery and has battery holders that are similar (Photo 6). You can expect about 2,000 mA-hours from AA cells. The 18650 Li-ion cells pack about three times the energy and they can be popped out and recharged in a few hours. Li-ion flat packs can also be used here, but they are not as “universal” as the 18650 single cells.

Photo 6
Replacing four AA cells with two 18650 Li-ion cells can save a lot of head scratching when unexpected behavior is due to battery droop. The AA cells (4 x 1.5 V) does not leave much headroom when a 5 V regulator is used. Not only is the discharge curve relatively flat for Li-ion cells (2 x 3.7 V) preventing drops in regulation, but the 18650 packs 3 times the energy.

It is a good idea to remove batteries from any equipment that will not be used for extended periods of time. Many devices today—like the ones with auto off functions—have parasitic circuits that continue to draw minuscule currents even when “off”. These will continue to draw down your batteries until they are unusable. Even though Li-ion cells have a protective circuit that prevents them from being discharged below a safe level—approximately 2.75 V/cell—this internal circuitry is parasitic and acts as a tiny load. While self-discharge is only a few percent per month, once the cell voltage drops below a critical voltage this circuitry may not allow it to be recharged. So always store a rechargeable in a “charged” state.

Wireless Charging today
Wireless charging is only in its infancy. Today’s phone chargers are typically less than 5 W. But there is work being done on higher rated equipment. It is proper that these low power devices have such safeguards built-in to prevent unwanted catastrophes. We know from the not too distant past that, along with higher power density materials, comes the potential for calamity unless the proper safeguards are in place. Public education can limit the misuse and/or abuse of lithium technology, just as it has for the safe handling and use of gasoline.

In order for the electric vehicle to become useful, we will need to replenish its range-defining battery charge in fairly short order. This requires extreme infrastructure changes. You can tell by the size of the connectors and cable required for this process that this is high power. The holy grail is for this to happen wirelessly and automatically. From a simple pad embedded in ground where you park your vehicle, to a highway infrastructure that transfers power to your vehicle while you drive. Wireless power transfer is here to stay. Nikola Tesla must be at peace knowing that his work is beginning to bear fruit.

Additional materials from the author are available


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