ARM mbed Platform for Bluetooth Smart Applications

OLYMPUS DIGITAL CAMERAThe nRF51822-mKIT simplifies and accelerates the prototyping process for Bluetooth Smart sensors connecting to the Internet of Things (IoT). The platform is designed for fast, easy, and flexible development of Bluetooth Smart applications.

The nRF51822 system-on-chip (SoC) combines a Bluetooth v4.1-compliant 2.4-GHz multiprotocol radio with an ARM Cortex-M0 CPU core on a single chip optimized for ultra-low-power operation. The SoC simplifies and accelerates the prototyping process for Bluetooth Smart sensors connecting to the IoT.

The nRF51822-mKIT’s features include a Bluetooth Smart API, 31 pin-assignable general-purpose input/output (GPIO), a CMSIS-DAP debugger, Programmable Peripheral Interconnect (PPI), and the ability to run from a single 2032 coin-cell battery.

Through mbed, the kit is supported by a cloud-based approach to writing code, adding libraries, and compiling firmware. A lightweight online IDE operates on all popular browsers running on Windows, Mac OSX, iOS, Android, and Linux OSes. Developers can use the kit to access a cloud-based ARM RVDS 4.1 compiler that optimizes code size and performance.

The nRF51822-mKIT costs $59.95.

Nordic Semiconductor ASA
www.nordicsemi.com

32-Bit Arm Cortex-M3 C Development Kit

ImageCraftThe CorStarter-STM32 is a complete 32-bit ARM Cortex-M3 C development kit. It includes hardware and software to develop and debug C programs in a simple to use package.

The CorStarter-STM32 base board is powered by a 72-MHz STM32 device with 256-KB flash and 64-KB SRAM. With 8-bit Arduino Shield-compatible headers, hundreds of Arduino Shields may be used to expand the system’s capabilities. Remaining I/O pins are brought out to the header, enabling access to full-power 32-bit embedded computing. The CorStarter-STM32 base board includes open-source hardware design files.

Fast code download and hardware debugging support are provided by either the industrial standard Segger JLINK-Edu or ST-LINK/V2. These JTAG/SWD pods enable full access to Cortex-M devices and seamless debugging without source code modification.

To complement the hardware, the CorStarter-STM32 kit also includes an ImageCraft non-commercial C compiler (ICCV8 for Cortex) license. The C compiler includes a professional IDE with an integrated flash downloader and a source-level debugger. The compiler can also be used for other Cortex-M development projects. The kit also includes example projects and libraries for various Arduino Shields.

The CorStarter-STM32 kit costs $99. The CorStarter-STM32 base board alone costs $55. For educators teaching embedded system courses, the kit costs $1.

ImageCraft
http://imagecraft.com

MCU-Based Projects and Practical Tasks

Circuit Cellar’s January issue presents several microprocessor-based projects that provide useful tools and, in some cases, entertainment for their designers.

Our contributors’ articles in the Embedded Applications issue cover a hand-held PIC IDE, a real-time trailer-monitoring system, and a prize-winning upgrade to a multi-zone audio setup.

Jaromir Sukuba describes designing and building the PP4, a PIC-to-PIC IDE system for programming and debugging a Microchip Technology PIC18. His solar-powered,

The PP4 hand-held PIC-to-PIC programmer

The PP4 hand-held PIC-to-PIC programmer

portable computing device is built around a Digilent chipKIT Max32 development platform.

“While other popular solutions can overshadow this device with better UI and OS, none of them can work with 40 mW of power input and have fully in-house developed OS. They also lack PP4’s fun factor,” Sukuba says. “A friend of mine calls the device a ‘camel computer,’ meaning you can program your favorite PIC while riding a camel through endless deserts.”

Not interested in traveling (much less programming) atop a camel? Perhaps you prefer to cover long distances towing a comfortable RV? Dean Boman built his real-time trailer monitoring system after he experienced several RV trailer tire blowouts. “In every case, there were very subtle changes in the trailer handling in the minutes prior to the blowouts, but the changes were subtle enough to go unnoticed,” he says.

Boman’s system notices. Using accelerometers, sensors, and a custom-designed PCB with a Microchip Technology PIC18F2620 microcontroller, it continuously monitors each trailer tire’s vibration and axle temperature, displays that information, and sounds an alarm if a tire’s vibration is excessive.  The driver can then pull over before a dangerous or trailer-damaging blowout.

But perhaps you’d rather not travel at all, just stay at home and listen to a little music? This issue includes Part 1 of Dave Erickson’s two-part series about upgrading his multi-zone home audio system with an STMicroelectronics STM32F100 microprocessor, an LCD, and real PC boards. His MCU-controlled, eight-zone analog sound system won second-place in a 2011 STMicroelectronics design contest.

In addition to these special projects, the January issue includes our columnists exploring a variety of  EE topics and technologies.

Jeff Bachiochi considers RC and DC servomotors and outlines a control mechanism for a DC motor that emulates a DC servomotor’s function and strength. George Novacek explores system safety assessment, which offers a standard method to identify and mitigate hazards in a designed product.

Ed Nisley discusses a switch design that gives an Arduino Pro Mini board control over its own power supply. He describes “a simple MOSFET-based power switch that turns on with a push button and turns off under program control: the Arduino can shut itself off and reduce the battery drain to nearly zero.”

“This should be useful in other applications that require automatic shutoff, even if they’re not running from battery power,” Nisley adds.

Ayse K. Coskun discusses how 3-D chip stacking technology can improve energy efficiency. “3-D stacked systems can act as energy-efficiency boosters by putting together multiple chips (e.g., processors, DRAMs, other sensory layers, etc.) into a single chip,” she says. “Furthermore, they provide high-speed, high-bandwidth communication among the different layers.”

“I believe 3-D technology will be especially promising in the mobile domain,” she adds, “where the data access and processing requirements increase continuously, but the power constraints cannot be pushed much because of the physical and cost-related constraints.”

Real-Time Trailer Monitoring System

Dean Boman, a retired electrical engineer and spacecraft communications systems designer, noticed a problem during vacations towing the family’s RV trailer—tire blowouts.

“In every case, there were very subtle changes in the trailer handling in the minutes prior to the blowouts, but the changes were subtle enough to go unnoticed,” he says in his article appearing in January’s Circuit Cellar magazine.

So Boman, whose retirement hobbies include embedded system design, built the trailer monitoring system (TMS), which monitors the vibration of each trailer tire, displays the

Figure 1—The Trailer Monitoring System consists of the display unit and a remote data unit (RDU) mounted in the trailer. The top bar graph shows the right rear axle vibration level and the lower bar graph is for left rear axle. Numbers on the right are the axle temperatures. The vertical bar to the right of the bar graph is the driver-selected vibration audio alarm threshold. Placing the toggle switch in the other position  displays the front axle data.

Photo 1 —The Trailer Monitoring System consists of the display unit and a remote data unit (RDU) mounted in the trailer. The top bar graph shows the right rear axle vibration level and the lower bar graph is for left rear axle. Numbers on the right are the axle temperatures. The vertical bar to the right of the bar graph is the driver-selected vibration audio alarm threshold. Placing the toggle switch in the other position displays the front axle data.

information to the driver, and sounds an alarm if tire vibration or heat exceeds a certain threshold. The alarm feature gives the driver time to pull over before a dangerous or damaging blowout occurs.

Boman’s article describes the overall layout and operation of his system.

“The TMS consists of accelerometers mounted on each tire’s axles to convert the gravitational (g) level vibration into an analog voltage. Each axle also contains a temperature sensor to measure the axle temperature, which is used to detect bearing or brake problems. Our trailer uses the Dexter Torflex suspension system with four independent axles supporting four tires. Therefore, a total of four accelerometers and four temperature sensors were required.

“Each tire’s vibration and temperature data is processed by a remote data unit (RDU) that is mounted in the trailer. This unit formats the data into RS-232 packets, which it sends to the display unit, which is mounted in the tow vehicle.”

Photo 1 shows the display unit. Figure 1 is the complete system’s block diagram.

Figure 1—This block diagram shows the remote data unit accepting data from the accelerometers and temperature sensors and sending the data to the display unit, which is located in the tow vehicle for the driver display.

Figure 1—This block diagram shows the remote data unit accepting data from the accelerometers and temperature sensors and sending the data to the display unit, which is located in the tow vehicle for the driver display.

The remote data unit’s (RDU’s) hardware design includes a custom PCB with a Microchip Technology PIC18F2620 processor, a power supply, an RS-232 interface, temperature sensor interfaces, and accelerometers. Photo 2 shows the final board assembly. A 78L05 linear regulator implements the power supply, and the RS-232 interface utilizes a Maxim Integrated MAX232. The RDU’s custom software design is written in C with the Microchip MPLAB integrated development environment (IDE).

The remote data unit’s board assembly is shown.

Photo 2—The remote data unit’s board assembly is shown.

The display unit’s hardware includes a Microchip Technology PIC18F2620 processor, a power supply, a user-control interface, an LCD interface, and an RS-232 data interface (see Figure 1). Boman chose a Hantronix HDM16216H-4 16 × 2 LCD, which is inexpensive and offers a simple parallel interface. Photo 3 shows the full assembly.

The display unit’s completed assembly is shown with the enclosure opened. The board on top is the LCD’s rear view. The board on bottom is the display unit board.

Photo 3—The display unit’s completed assembly is shown with the enclosure opened. The board on top is the LCD’s rear view. The board on bottom is the display unit board.

Boman used the Microchip MPLAB IDE to write the display unit’s software in C.

“To generate the display image, the vibration data is first converted into an 11-element bar graph format and the temperature values are converted from Centigrade to Fahrenheit. Based on the toggle switch’s position, either the front or the rear axle data is written to the LCD screen,” Boman says.

“To implement the audio alarm function, the ADC is read to determine the driver-selected alarm level as provided by the potentiometer setting. If the vibration level for any of the four axles exceeds the driver-set level for more than 5 s, the audio alarm is sounded.

“The 5-s requirement prevents the alarm from sounding for bumps in the road, but enables vibration due to tread separation or tire bubbles to sound the alarm. The audio alarm is also sounded if any of the temperature reads exceed 160°F, which could indicate a possible bearing or brake failure.”

The comprehensive monitoring gives Boman peace of mind behind the wheel. “While the TMS cannot prevent tire problems, it does provide advance warning so the driver can take action to prevent serious damage or even an accident,” he says.

For more details about Boman’s project, including RDU and display unit schematics, check out the January issue.

Low-Cost, High-Performance 32-bit Microcontrollers

The PIC32MX3/4 32-bit microcontrollers are available in 64/16-, 256/64-, and 512/128-KB flash/RAM configurations. The microcontrollers are coupled with Microchip Technology’s software and tools for designs in connectivity, graphics, digital audio, and general-purpose embedded control.

The microcontrollers offer high RAM memory options and high peripheral integration at a low cost. They feature 28 10-bit ADCs, five UARTS, 105-DMIPS performance, serial peripherals, a graphic display, capacitive touch, connectivity, and digital audio support.
The PIC32MX3/4 microcontrollers are supported with general software development tools, including Microchip Technology’s MPLAB X integrated development environment (IDE) and the MPLAB XC32 C/C++ compiler.

Application-specific tools include the Microchip Graphics Display Designer X and the Microchip Graphics Library, which provide a visual design tool that enables quick and easy creation of graphical user interface (GUI) screens for applications. The microcontrollers are also supported with a set of Microchip’s protocol stacks including TCP/IP, USB Device and Host, Bluetooth, and Wi-Fi. For digital audio applications, Microchip provides software for tasks such as sample rate conversion (SRC), audio codecs—including MP3 and Advanced Audio Coding (AAC), and software to connect smartphones and other personal electronic devices.

The PIC32MX3/4 family is supported by Microchip’s PIC32 USB Starter Kit III, which costs $59.99 and the PIC32MX450 100-pin USB plug-in module, which costs $25 for the modular Explorer 16 development system. Pricing for the PIC32MX3/4 microcontrollers starts at $2.50 each in 10,000-unit quantities.

Microchip Technology, Inc.
www.microchip.com