Students and newcomers in the field often ask me: “Teacher, is a microcontroller unit (MCU) the same as a system on chip (SoC)? I see different opinions online, and I’m a bit confused. Today, let’s discuss this topic.
To conclude: it is primarily an MCU, but it is increasingly resembling a SoC.
1.MCU
MCU stands for microcontroller unit. The key focus is on control, as the main purpose of designing an MCU is to control. It controls motors in washing machines, small devices in factories, etc.
The essence of being a single chip: it integrates all the core components needed to accomplish the control task into a single chip.
Clear objectives: An MCU chip can be soldered onto a circuit board, and with a power supply, crystal oscillator, and a few necessary components, it can operate independently. It is designed for embedded control.
Characteristics of an MCU: Highly integrated, CPU+ memory+ storage+ rich peripherals, all essential components for control, low cost, and low power consumption.
2.What about SoC?
SoC stands for system on chip. The key focus is on the system, which is not just for control; the goal is to implement the core functions of a complete and more complex electronic system on a single chip.
1. Higher integration and complexity:
It must contain one or more powerful CPU cores, possibly complex application processors, like the ARM Cortex-A series found in smartphones. Generally, it includes powerful graphics processing units (GPUs) to handle complex image displays, such as those on smartphone screens and smartwatches.
It has dedicated hardware acceleration modules, for tasks like video encoding/decoding, AI computations. It integrates various high-speed, complex communication interfaces, and may also include numerous memory controllers. It resembles a small computer’s motherboard, with core components like CPU, GPU, and high-speed interface controllers all packed into one chip.
2. Requires external support:
An SoC generally cannot be used as simply as an MCU can. It needs to be paired with external large-capacity memory, external large-capacity storage, a more complex power management system, multiple clock sources, and an operating system to manage these complex resources.
Applications: smartphones, tablets, smart TVs, set-top boxes, high-end smartwatches, some IoT gateways, automotive entertainment systems, etc. For example, Qualcomm Snapdragon, Apple A series, and Huawei Kirin chips are all SoCs, and the core chip of Raspberry Pi is also an SoC.
Characteristics of SoC: ultra-high integration, particularly complex functions, aimed at system-level applications, requiring external large memory, storage, complex power management, operating system support, strong performance, and relatively high power consumption.
3.Which category does a microcontroller fall into?
Traditional microcontrollers like 51, AVR, PIC, and basic STM32 series are purely MCUs. Their structure is relatively simple, and their integration meets the control requirements, with peripherals designed around control tasks, allowing them to run bare metal or RTOS without complex external components.
Some high-performance, multifunctional microcontrollers today, such as certain STM32H7 series with powerful DSPs, rich network interfaces, and large memory, or ESP32-S3 with integrated WiFi and Bluetooth, are a bit ambiguous; they can be considered MCU-level SoCs.
They are still fundamentally about embedded control, but they are designed for more complex applications, such as running simple UIs, performing audio processing, or running lightweight Linux. Their integration is higher, incorporating features that traditionally belong to SoCs, such as faster CPUs, larger on-chip RAM, richer high-speed interfaces, and even dedicated accelerators.
However, they generally do not require large external DDR memory like smartphone SoCs, nor do they run large Android or Linux, so their overall complexity and power consumption are still lower than typical SoCs.
4.How to choose for development?
Selection based on requirements: If you want to make a temperature and humidity meter to control a small motor, using a 51 core MCU is sufficient, as it has strong real-time capabilities.
If you want to create a small smart device that needs to connect to WiFi, run a lightweight OS to handle complex logic, an enhanced MCU like ESP32 or STM32H7 would be very suitable, balancing power consumption, real-time performance, and functionality.
If you want to do video surveillance, run complex user interfaces, or require extensive network interactions, you may need to consider using an SoC.
Focus on core architecture: The ARM Cortex-M series is designed for real-time control in MCUs. The Cortex-A series is designed for application processors in SoCs. By looking at the core used in the chip, you can generally determine which category it belongs to.
So now we can understand this: an MCU is a subset of SoCs, specifically designed for control. MCUs are becoming increasingly powerful, integrating more components, and resembling the core of a system, gradually overlapping with SoCs. However, its roots still lie in control.