FPGA vs. Microcontroller – Understanding the Key Differences

Microcontrollers and field programmable gate arrays (FPGAs) are both often utilized in digital system design. Microcontroller-based systems are becoming increasingly popular. On one hand, their low cost, low power consumption, and suitability for basic control tasks make them an obvious choice. On the other hand, the rapidly expanding popularity of FPGAs, the availability of robust development tools, and their increased parallel processing capability and density make FPGA-based systems an attractive option.

Several microcontroller cores are available for the embedded market today, ranging from conventional designs such as the 8051 to RISC or DSP machines. The decision between different designs is determined by criteria such as speed, power, installed base, potential for reuse, and other technical considerations. Embedded applications are an ever-expanding subject of study in computer systems. The MCU's large number of communication ports, Pulse Width Modulation (PWM) units, and Analog-to-Digital Converters (ADC) packed into a single chip make it ideal for industrial applications.

In various fields of electrical engineering, MCUs are typically used for basic control, communication, and low-complexity tasks, while Field Programmable Gate Arrays (FPGAs) are employed for high-speed, time-critical processing tasks. However, applications based on devices integrated into consumer electronics have various design restrictions. In this circumstance, power consumption, code density, and peripheral integration might take precedence over performance requirements. On the other hand, from a technological standpoint, the growing densities of FPGAs and the drop in their prices due to high manufacturing volume enable the integration of embedded systems in a single FPGA chip.

What is a Microcontroller?

A microcontroller is an electronic device that belongs to the microcomputer family. The components of the microcontroller are fabricated with the help of Very Large Scale Integration (VLSI) to form a single chip. They are also known as Computer-on-chip. A microcontroller has a certain amount of RAM and ROM (EEPROM, EPROM, etc.) or flash memories for storing program codes. Additional features are timers, parallel ports, serial ports, interrupt ports, ADC, PWM, and DAC. A microcontroller is a microprocessor with memory and I/O capabilities. Microcontrollers are widely used in embedded systems due to their integration of CPU, memory, and I/O peripherals into a single chip.

A PC or laptop is a general-purpose machine (used for various tasks such as gaming, browsing the Internet, music, word processing, etc.). In contrast, embedded systems are typically single-function devices designed for specific tasks. A key characteristic of microcontroller systems is that they often perform dedicated tasks without needing a full-fledged operating system (e.g., Windows, Linux, macOS, iOS). Watches, MP3 players, vending machines, and other electronic devices contain embedded systems. A complete computer would sometimes interfere with the device's functionality. Imagine needing to start Windows to operate a dishwasher. Figure 2 depicts the architecture of a microcontroller.

Compilers verify that high-level programming language code is valid, both in grammar and memory allocation. In these circumstances, faults or warnings are often presented, and error-containing codes are not stored on the microcontroller. Once the code is correct, the compiler transforms it into machine code and outputs a HEX file that is loaded into the microcontroller's memory.

What is an FPGA (Field Programmable Gate Array)?

Field programmable gate arrays (FPGAs) are digital integrated circuits (ICs) that include changeable (programmable) logic blocks and interconnects. Design engineers may program such gadgets to execute a wide range of functions. Depending on how they are constructed, certain FPGAs may only be programmed once, whilst others may be programmed repeatedly. Unsurprisingly, a device that can only be programmed once is known as a one-time programmable.

The "field-programmable" part of the FPGA's name alludes to the fact that programming occurs "in the field" (as opposed to devices whose core functionality is hard-wired by the manufacturer). This might apply to configuring FPGAs in the lab or changing the operation of a device in an electronic system that has already been deployed in the real world. If a device can be programmed while staying in a higher-level system, it is said to be in-system programmable. Figure 3 depicts the development board for the FPGA.

FPGAs are frequently employed as coprocessors for existing processors, either to accelerate time-critical tasks or to extend the functionality of typical ALUs. For example, when using microcontrollers, calculating equations with more than two terms necessitates a series of arithmetic and/or logical operations, and in many circumstances, a temporary variable must be assigned. FPGAs can improve the performance of such systems by completing such computations in parallel while using a fair amount of combinational logic.

They are also commonly employed in custom-computing systems, where a whole computational device is created and implemented in an FPGA. Single-chip microcontrollers are often used and sufficient for certain application needs. In this instance, only the software for the desired application needs to be written. The hardware interface is essential for designing such systems and is often implemented using standard specialized chips. This results in a fixed system that cannot be changed without a hardware redesign. FPGAs offer significant flexibility in these applications, allowing for hardware customization and parallel processing. Figure 4 represents the internal block diagram of an FPGA development board.

Key differences between Microcontrollers and FPGA

Performance

As microcontrollers depend on clock speed, they usually have lower performance than FPGAs as their frequency is design dependent. Most of these applications are image and video processing.

Power Consumption

Microcontrollers (MCUs) consume less power than FPGAs because of the compact size of microcontrollers. Microcontrollers are ideal for running batteries, inverters, and converters. On the other hand, FPGAs are better in digital processing for image and video processing.

Flexibility and Customization

The hardware setup is flexible while running in FPGAs, while in microcontrollers all the alterations are done through software development. This thing made microcontrollers less flexible than FPGAs. Software-based customization is favorable in MCUs while hardware-based customization is easier in FPGAs.

Development Time and Complexity

MCUs and FPGAs differ in terms of memory architecture and performance characteristics. A microcontroller has non-volatile memory, which means after power OFF, MCUs retain their memory, while this feature is absent in FPGAs because of Random Access Memory in FPGAs. Microcontrollers are typically programmed using high-level languages like C/C++, while FPGA development requires hardware description languages such as Verilog or VHDL. Verilog and FPGAs are hardware supported while C/C++ are software supported languages.

Similarities between Microcontroller and FPGA?

Basic Components

A microcontroller is nothing while integrated with integrated circuits (ICs), while FPGAs mostly contain ICs and other integrated circuits. In short, both technologies are a blend of both integrated circuits and high-level language.

Customization

After manufacturing, both FPGAs and microcontrollers are re-programmable, and alteration in their function can be done after building the infrastructure. However, FPGAs are mostly suited for high applications, while MCUs like Arduino are well suited for simpler applications as well.

Applications for FPGAs and Microcontrollers

Microcontrollers are widely available at low cost and offer a wide range of features for power and electronics applications. However, using MCUs requires expertise in high-level languages such as C/C++. On the other hand, FPGAs are higher in price but are much user friendly. Microcontrollers work efficiently at low power, which lessens the need for energy. On the other hand, FPGAs require high power, which demands more energy for operation. Software-based solutions are not directly customized, while Hardware-based solutions are directly customized. Inverters, UPS, and converters are ideal applications for MCUs, while video and image processing are more suited to FPGAs due to their parallel processing capabilities.

When to use FPGAs and Microcontrollers

Although, both are application dependent. Designers and engineers found MCUs more sophisticated in embedded systems due to their compact size and most of the applications have size constraints like DC-DC converters and many other power electronics applications. On the other hand, FPGAs are durable and efficient in artificial intelligence, image processing, and video processing. FPGAs are user-friendly and can handle heavy calculations much faster than MCUs. Less expertise is required by the user to use FPGAs than MCUs.

FPGA vs others

The differences between FPGA, CPLD, and MCUs are described in this section.

FPGA vs CPLD

FPGA vs Microprocessor

Conclusion

MCUs and FPGAs both are beneficial for a lot of digital, electrical, and power applications. Microcontrollers are economical, consume low power, and are software-favorable, while FPGAs are costly, consume high power, and are hardware-friendly but have high performance and ease of parallel processing. MCUs retain their functions although power is OFF because of RAM, while this feature is absent in FPGAs because of their volatile memory. Although both apply to design-based technologies, a user may consider power consumption, development time, parallel processing, and flexibility for an application where MCUs are FPGAs both can be used.