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The microcontroller is one of the most commonly used components in IoT deployments, but picking the right one for each IoT project requires some consideration.
The small, integrated circuit typically includes a processor, memory, and input and output peripherals -- all of which are contained on a single chip. It's dedicated to control a limited number of functions -- often just a single operation, such as regulating the operations of electromechanical systems in a device. The microcontroller design performs a specific task, and then it's embedded into a system where it perpetually runs that function.
A microcontroller unit (MCU) with its contained RAM, ROM and peripherals devices can operate independently. Independent operation, especially when combined with its small size, makes it a natural fit for IoT deployments. It's also energy efficient, which means it has low operational costs and can support extended mobility and remote deployments. Its software-controlled architecture makes it agile.
"When you think about all of the intelligent things, gadgets and devices in the IoT, you are really talking about the world of microcontrollers. In many cases, MCUs are the brains of these small devices that often have very specific requirements for processing response, battery life or sensor data collection," said Christopher Rommel, executive vice president of IoT and industrial technology at VDC Research.
Growing demand for IoT microcontrollers
More than 30 billion microcontroller units were shipped in 2019, according to a February 2020 report from Grand View Research. The research firm said increased demand for embedded control systems in multifunctional devices, such as vehicles, robots, medical devices, mobile radio and residential appliances drives the market.
Grand View Research put the size of the global microcontroller market at $20.82 billion in 2019 and predicted it will reach $47.74 billion by 2027, with a compound annual growth rate of 10.8% expected over the next seven years. The firm attributed that growth to increasing automation and AI applications in both the automotive and industrial segments.
"Microcontrollers are one of the most widely used processor types in the IoT market. In fact, there are over 85 times as many MCUs used in IoT/embedded applications than there are CPUs," Rommel said.
Functions of microcontrollers for IoT
A microcontroller brings intelligence to IoT, said Kevin Eichhorst, senior principal solution architect in the Wireless Design Services division at Digi International, a provider of IoT connectivity products and services.
Consider the use of a sensor to determine whether a tank is empty, full or somewhere in between. The sensor can take the measurement, but a radio-integrated microcontroller must make sense of the measurement and direct that information back to a central point, such as a monitoring station.
"Microcontrollers are bringing automation to distributed segments of IoT solution networks by enabling autonomous execution of solution processes, where coordination decisions are taken at the edge," said Miroslaw Ryba, global IoT leader at professional services firm EY.
However, not all IoT deployments use MCUs. Some use CPUs, field-programmable gate arrays, application-specific integrated circuits or GPUs. Larger IoT technologies, such as gateways and edge servers, require less specialized compute and often use CPUs that offer more performance and support for more general-purpose software and operating system stacks instead.
"However, even in those cases when an IoT device might use another type of processor as the primary compute unit in the system, MCUs can often still be used for subsystem and peripheral compute in more complex designs," Rommel said. "Their utility for addressing real-time, sensor-based and redundancy needs make them a clear choice for many projects."
Selecting a microcontroller
There are numerous IoT microcontroller manufacturers, product types – including 8 bit, 16 bit and 32 bit -- and use cases that further segment the market, which makes selection criteria an important part of IoT design.
"The core factor-defining specification of [an IoT microcontroller's] components would be the use case itself, which defines a set of required functional, nonfunctional characteristics," Ryba said.
Corporate technology policies, as well as market and government regulations, should also influence selection decisions. Experts said selection criteria include:
- functional and nonfunctional use applicability;
- support and development factors;
- operational costs;
- environmental, health and safety risks, along with related mitigation costs; and
- cybersecurity risks exposure.
IoT engineers should also consider the microcontroller's interfaces, as well as how much memory the MCUs has, its speed and power consumption, Eichhorst said. For example, engineers might need to know if the microcontroller integrates with Bluetooth.
Miroslaw RybaGlobal IoT leader, EY
Engineers should consider external factors such as whether the microcontroller will be part of an IoT deployment used in extreme temperatures or conditions, Eichhorst said. Microcontrollers used in systems in space, for instance, must be radiation-hardened.
Experts also stressed the need for broad thinking when selecting the right microcontrollers for IoT projects.
"It is critical that engineering organizations now think beyond speeds and feeds when thinking about their MCU selection, instead focusing on the MCU's impact on the entire device design and deploy lifecycle," Rommel said. "Of particular note is the value that an MCU supplier should bring to the software development process, given the latter's importance to IoT device functionality and differentiation."
Rommel's firm polled engineers about what was most important to them in the selection of processors and found that an increasing number cited software and tool-related criteria.
"Beyond the growing importance of having access to a suite of integrated software and development solutions to help accelerate development, it is often important to consider the other unique requirements of a design when choosing an MCU. Long lifecycle support can be very important in the industrial sector as can power consumption considerations for any battery-powered device," Rommel said.