Are Microcontrollers Up For the Challenge of the Internet of Things?Are Microcontrollers Up For the Challenge of the Internet of Things?

If there’s one rule about choosing a microcontroller (MCU) for the Internet of Things, it’s that most of the old rules don’t apply.

Internet of Things (IoT) applications are a breed apart. They need to communicate. They need lots of software and memory. And they might need to work forever without a battery charge.

And, oh, they need microcontrollers to make it all happen.

“In the IoT, there’s a whole different set of concerns that people who build parts with microcontrollers never had to worry about before,” said Manas Saksena, senior director of technology and product marketing at Marvell Semiconductor. “If someone is operating in that old world of microcontrollers, they can’t build networked IoT products successfully.”

Indeed, embedded IoT products do present a different set of challenges, but a growing number of IoT-targeted MCU solutions are already available and making an impact in high-profile products. Marvell, for example, has placed its EZ-Connect 88MW300 WiFi microcontroller in a wide variety of IoT applications, ranging from connected air and water purifiers to smoke alarms to smart light bulbs. The light bulb, known as the Yeelight LED and manufactured by Xiaomi Inc., allows users to control it with a smartphone. Similarly, the company has incorporated its 88MW300 microcontroller platform in Mattel’s Hello Barbie doll, which requires a WiFi connection to allow for two-way conversation. The IoT platform enables the doll to play interactive games, store up to 8,000 lines of dialogue, and remember up to three different WiFi locations.

“It does what Siri does on your [iPhone],” said Saksena. “You can carry on real-time, interactive conversations with Barbie.”

Applications such as those require significant computing power, of course. Marvell’s 88MW300 includes an ARM Cortex-M4F CPU, 802.11 b/g/n WiFi, and 512 kB of SRAM. Similarly, Renesas Electronics offers an MCU platform called Synergy. Tailored for IoT applications, Synergy was launched in October with the 48-MHz S3A7 and the 240-MHz S7G2, both of which are based on ARM Cortex-M4 cores.

A Need for Low Power

One key to serving in such applications, however, is the ability to offer that high performance without exceeding an excruciatingly tight energy budget. “Low power is important because so many IoT applications require always-on operation,” said Amit Hammer, product line manager for Bluetooth Smart Cortex-M applications at Texas Instruments (TI). “Some use energy harvesting, where low-power operation is critical.”

TI’s solution lies in its SimpleLink platform. One of the early members of the platform, the CC2640 MCU, operates at active power levels of 6 mA and draws just 1 µA of current in sleep mode. The CC2640 is well suited for the IoT, TI says, because it’s a one-chip solution that includes an ARM Cortex-M3-based MCU, a radio using a separate Cortex-M0 core, and a sensor-controller engine. It also offers pin- and code-compatibility across Bluetooth Smart, 6LoWPAN, and ZigBee.

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The power consumption of some MCUs is so low that they can run indefinitely without batteries. Cypress Semiconductor’s PSoC 4 BLE system-on-chip and PRoC BLE radio-on-chip devices, for example, can be teamed with an energy-harvesting chip and run off the current from a solar cell the size of a quarter. “You can take our radio, put it on a board with a PSoC part, put a solar cell on the other side, and you have yourself a zero-maintenance system,” said John Weil, vice president of marketing for Cypress. “It will send data for the rest of your existence and no batteries ever have to be charged.” The PSoC and PRoC duo, he added, offers heightened IoT security because they are Bluetooth 4.2 qualified.

Simplicity Is Key

Even with the availability of such impressive new technology, however, experts say the temptation for developers to use familiar hardware and tools will be a problem for many going forward. It’s easy, they say, to stay with products that have worked in the past. Familiarity means engineers don’t have to scramble up a new learning curve. But it also means they’ll have to pull parts from various sources, rather than having everything pre-integrated on one chip.

MCU manufacturers are combating that with platforms that focus on simplicity. By offering a cleaner, simpler development path, they hope engineers will reach for their tailor-made IoT tools. Renesas’ Synergy platform, for example, incorporates software and middleware along with each controller. While Renesas was creating the platform, it partnered with 11 software companies with expertise in wireless, middleware, security, embedded boards, and cloud-based services. The company even went so far as to tailor its hardware to the software, which is believed to be a first in the embedded world.

“We originally looked at doing a software platform on top of an existing product line,” said Vin D’Agostino, vice president of the General Purpose Products Unit at Renesas. “But we decided, no, if we were going to do this, we wanted the interface between the software and hardware to be as efficient and secure as possible.”

And simple. Because an IoT software component is so big, and developers aren’t always trained in the software arena, Renesas decided that simplicity would be a key. “It’s exactly targeted at designers who don’t have a lot of development resources in-house,” D’Agostino said. As such, the company’s Synergy software solutions include a ThreadX real-time operating system (RTOS), network stacks, app bundles, GUI frameworks, and board support packages.

Similarly, TI’s SimpleLink platform focuses on reducing complexity. The platform includes the TI RTOS, Code Composer Studio integrated development environment, online training, and community support. No RF expertise is required, TI says. “You want to have a platform that requires minimal RF experience,” said TI’s Hammer. “You have to have a robust real-time operating system, tools, and development kits, so you can go right out of the box and start prototyping very quickly.”

Such platforms are becoming increasingly necessary, manufacturers say, because IoT applications are so much different than standard embedded apps. Embedded products that were previously designed with an isolated MCU must now migrate to a world of networked communication. And as that happens, complexity increases.

“The whole microcontroller world is going through a shift,” noted Marvell’s Saksena. Until now, most products built around microcontrollers didn’t have to communicate. Now, they do. So it boils down to this: How do you intend to get those products networked?” DN

Senior technical editor Chuck Murray has been writing about technology for 31 years. He joined Design News in 1987, and has covered electronics, automation, fluid power, and autos.

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