Microcontrollers in Embedded Systems: Design, Selection, and Best Practices

Smart devices, appliances, and systems are now deeply integrated into everyday life, from home automation to industrial processes. These systems rely on a central processing unit to make decisions and execute tasks. In the case of smart electronics, this role is played by an embedded system. An embedded system is a specialized circuit board, often referred to as a PCBA (Printed Circuit Board Assembly), that includes a microcontroller—a compact, self-contained computing unit designed for specific functions. Unlike general-purpose computers such as desktops and laptops, microcontrollers are optimized for dedicated tasks and operate without running multiple applications. Designing efficient embedded systems requires a strong understanding of microcontroller features and capabilities.

Catalog

Figure 1: Microcontrollers: The Brains of Smart Electronics Everywhere

How Microcontrollers Are Used

Embedded system design was historically known as microprocessing, a term that stemmed from the use of microprocessors (MPUs). A microprocessor is essentially the central processing unit (CPU) of a system, requiring external components to function effectively. In contrast, a microcontroller (MCU) integrates all necessary computing elements—such as memory, processing power, and input/output interfaces—into a single integrated circuit (IC). This compact integration makes MCUs more suitable for embedded applications where space, efficiency, and cost constraints are critical.

The increasing adoption of circuit boards equipped with these ICs led to the broader term "embedded systems." While microcontrollers have evolved, their fundamental architecture remains similar to traditional computers, including essential components like RAM, ROM, a clock or timer, a CPU, and I/O interfaces.

Most microcontrollers come with built-in ROM (such as EPROM or EEPROM) preloaded with firmware designed to execute specific functions. However, modern microcontrollers increasingly utilize flash memory, which allows for flexible programming and reprogramming. This is particularly useful for development boards, where the firmware can be updated off-board before being transferred to the final system. In many cases, in-circuit programming and debugging are also possible if the system supports external data and power transmission through its bus interface.

The rapid expansion of smart technology has extended microcontroller applications beyond consumer devices. Today, they play an essential role in industrial automation, process control, and manufacturing systems. Below are some key applications of microcontrollers:

Common Microcontroller Applications

Industrial automation – Used in robotics, motor control, and automated production lines.

Device process control – Found in temperature controllers, feedback systems, and industrial machinery.

Data acquisition (DAQ) and signal processing – Essential for collecting, analyzing, and transmitting sensor data.

Internet of Things (IoT) systems – Serve as the backbone of connected devices in smart homes and industrial IoT applications.

Standalone automated products – Used in vending machines, self-service kiosks, and automated security systems.

Sensor-based operations – Applied in motion detection, environmental monitoring, and smart agriculture.

Key Features of Microcontrollers

Microcontrollers come in many varieties, and choosing the right one depends on the requirements of the specific application. A well-structured design should match the microcontroller’s features to the intended use. One of the most commonly used microcontroller families is the PIC series from Microchip Technology, including the high-performance PIC32MK.

The PIC32MK Microcontroller

Figure 2: 64-Pin PIC-32 MCU in TQFP Package

The PIC32MK is a 32-bit microcontroller available in multiple package options, including 64-pin TQFP, 64-pin QFN, and 100-pin TQFP. This microcontroller is optimized for motor control applications but can also handle various embedded system tasks. Key specifications include:

Core and Processing Capabilities

MIPS32® microAptiv™ core with a Floating Point Unit (FPU)

Advanced memory control for efficient data handling

Up to 16 kB of flash memory

Analog and Digital Features

7 ADC modules for precise analog-to-digital conversion

3 12-bit capacitive analog-to-digital converters (CDACs)

4 operational amplifiers (op-amps) and 5 comparators

Timers and Signal Processing

Up to 14 16-bit or 8 32-bit timers, plus an additional 16-bit timer

6 Quadrature Encoder Interface (QEI) 32-bit timers for motion tracking

16 input capture modules and 16 output compare modules

A real-time clock and calendar module

Communication Interfaces

4 CAN bus modules for automotive and industrial applications

6 UART modules for serial communication

6 SPI/I2S modules for peripheral connections

Up to 2 Full-Speed USB controllers

Motor Control and Special Functions

Motor Control Pulse Width Modulation (PWM) capability

Motor encoder interface for precise speed and position tracking

Internal temperature sensor for thermal monitoring

In-Circuit Serial Programming™ (ICSP™) support

JTAG interface for debugging and testing

The PIC32MK’s architecture integrates features that reduce the need for additional components, particularly in motor control applications. This simplifies PCB layout and reduces system complexity.

Figure 3: PIC32MK Block Diagram

Alternative 32-bit PIC Microcontrollers

While the PIC32MK is a powerful choice, other 32-bit PIC microcontrollers from Microchip offer different performance levels, memory configurations, and power consumption profiles. Some alternatives include:

PIC32MZ Series

PIC32MZ EF – 252 MHz, 512 kB to 2 MB Flash, 128 to 512 kB SRAM

PIC32MZ DA – 200 MHz, 1 to 2 MB Flash, 256 to 640 kB SRAM

PIC32MX Series

PIC32MX 3/4 – 80 to 120 MHz, 32 to 512 kB Flash, 8 to 128 kB SRAM

PIC32MX 5/6/7 – 80 MHz, 64 to 512 kB Flash, 16 to 128 kB SRAM

PIC32MX 1/2 XLP – 72 MHz, 128 to 256 kB Flash, 32 to 64 kB SRAM

PIC32MX 1/2/5 – 50 MHz, 16 to 512 kB Flash, 4 to 64 kB SRAM

Other Microchip Microcontrollers

PIC32CM MC – ARM® Cortex® core, 48 MHz, 64 to 128 kB Flash, 8 to 16 kB SRAM

PIC32MM – 25 MHz, 16 to 256 kB Flash, 4 to 32 kB SRAM

For simpler applications, Microchip also provides 8-bit and 16-bit microcontrollers, which offer reduced instruction sets and simpler programming while maintaining efficiency.

Best Practices for Embedded PCBA Design

Figure 4: PIC32MK Model Data from Ultra Librarian

When integrating microcontrollers into PCB designs, several factors influence performance and reliability:

Trace Routing and Board Layout – The PIC32MK’s 64-pin configuration often requires a multilayer PCB design. Efficient trace routing and via placement help minimize board size while maintaining signal integrity.

Power Management – Proper decoupling capacitors near power pins stabilize voltage levels and reduce noise.

Programming Access – To take full advantage of in-circuit and in-application programming, ensure that debugging and programming headers are accessible.

Thermal Considerations – Components such as the internal temperature sensor allow real-time monitoring, but PCB design should also incorporate proper heat dissipation strategies, such as ground planes and thermal vias.