Recently, some friends asked me how to learn embedded systems. I have always wanted to write an article about the learning path, but due to various reasons, it was delayed until now. I have finally completed this article.
I personally transitioned from STM32 to driver development. During my second year of research, I studied the driver development course by Teacher Wei Dongshan and shifted towards driver development. Below, I will share my personal views on how to learn embedded systems.
1. What is Embedded?
Embedded refers to embedded systems, which the IEEE (Institute of Electrical and Electronics Engineers) defines as devices used to control, monitor, or assist in operating machines and equipment. It is a type of dedicated computer system.
The commonly accepted definition of embedded systems in China is application-centered, based on computer technology, with customizable hardware and software that meets strict requirements for functionality, reliability, cost, size, power consumption, etc.
From the perspective of application objects, embedded systems are a combination of software and hardware, and can also encompass mechanical and other auxiliary devices. As part of a device, it is a control program stored in the ROM of an embedded processor control board.
In fact, all devices with digital interfaces, such as watches, microwaves, VCRs, cars, etc., use embedded systems. Some embedded systems also include operating systems, but most embedded systems implement the entire control logic with a single program.
2. Embedded Directions
Embedded engineers need to master a wide range of content, mainly including embedded software, embedded hardware, and professional knowledge related to industries and products. As beginners in embedded systems, we cannot, nor do we have the energy to master all knowledge proficiently. We must learn to focus on key points, learn to prioritize, and achieve effective learning. Embedded technology is mainly divided into two major directions: embedded software and embedded hardware.
1. Embedded Hardware Direction
The main responsibilities of embedded hardware engineers are to design hardware circuit schematics, design hardware PCB boards, select suitable components, solder and debug hardware circuit boards, and ensure the reliability, stability, and anti-interference capability of hardware circuit boards.
Due to the rapid development of integrated circuits, most integrated circuit manufacturers provide reference circuits, making the design of hardware circuit schematics relatively simple. The value of hardware engineers mainly lies in the design of reliability and stability, as well as electromagnetic compatibility, which is where the value of hardware design engineers lies.
Becoming a senior embedded engineer is quite difficult. On one hand, one must have very solid theoretical knowledge, and on the other hand, considerable experience in designing large, high-frequency CPUs, and multi-layer PCB boards.
Courses that embedded hardware engineers need to learn mainly include analog circuit design, digital circuit design, and electromagnetic wave theory. Familiarity with common amplifier circuits, filter circuits, and power circuit design and analysis is also essential.
2. Embedded Software Direction
The main responsibility of embedded software engineers is to design software according to product functional requirements to make the hardware work.
The hardware part of embedded electronic products is mostly the same, primarily consisting of CPU, RAM, and FLASH, while the software varies significantly. The specific functions of a product are implemented by software, and generally, the workload of software design is 4 to 5 times that of hardware design.
Therefore, typically, the number of software engineers in a company is 4 to 5 times that of hardware engineers. The demand for embedded software engineers is much greater than that for hardware engineers. Additionally, compared to hardware engineers, embedded software engineers find it relatively easier to learn, so I will focus on the learning path of embedded software engineering.
3. What Knowledge is Needed to Learn Embedded?
1. C Language
C language is the core of embedded systems. The Linux operating system is implemented in C, and the underlying part of the Android system is also implemented in C. A solid foundation is essential.
During the learning process of C language, focus on pointers, structures, file handling, and arrays. While learning, it is important to write a lot of code; just reading code won’t help you learn.
Don’t be afraid of trouble when encountering errors; be adept at using search tools like Baidu, Google, and Stack Overflow. Remember, the problems you encounter have likely been faced by others, and a quick search online will usually yield answers.
Finally, debugging programs often is crucial. Writing a program is only a third of the work; seven parts are debugging. No one’s program is written correctly on the first try. Moreover, debugging programs can help us understand how the program executes in detail.
2. Basic Hardware Principles
Embedded systems inevitably involve working with hardware. If you are working on the application layer of embedded systems, you may have less interaction with hardware. However, many companies will ask about basic hardware knowledge during interviews.
For example, a classmate of mine was asked many hardware-related questions (such as what interrupts are, what polling is, the differences between the two, and what constitutes a basic embedded system) when interviewing for a C++ engineer position at MediaTek. Hence, the more hardware knowledge you have, the better. Even if you work on the application layer, you should know some basics.
If you plan to work on the embedded bottom layer, the requirements for mastering hardware knowledge are higher. For example, how LCD displays information, what IIC protocol/SPI protocol is, how to transmit and receive data, the speed requirements for different devices regarding IIC, and the typical pull-up resistor value for IIC protocol, etc. Only by understanding hardware principles can you understand how to configure various registers when reading chip manuals.
Additionally, it would be great to master the use of common devices and instruments that come in handy when discussing with hardware engineers, such as multimeters, oscilloscopes, and logic analyzers. However, it’s okay if you don’t know these; they are not mandatory.
3. Data Structures and Algorithms
This part is essential for programmers. In the autumn and spring recruitment tests of major companies, this is a must-test area. Common data structures like linked lists, binary trees, heaps, queues, and common sorting algorithms and their improvements (quick sort, merge sort, bubble sort, insertion sort) are necessary to master. If you’re looking for a job, you should be able to write these from memory.
Although embedded systems do not require as high a level of data structures and algorithms knowledge as traditional internet development, and these structures may not always be used in future work, we should still know some basics.
For instance, the Linux kernel uses many linked lists and binary trees. Mastering this content will greatly help us in job-hopping and in-depth research into operating systems.
4. Computer Basics
This part directly determines whether we can progress further in our careers. Concepts like the basics of operating systems and computer organization principles are essential to understand, such as spin locks, semaphores, blocking and non-blocking, etc.
If you have time, I recommend following online courses to learn these topics thoroughly. Many such courses are available on platforms like Bilibili and Xuetang Online. Later, I will write an article about which quality courses are worth our attention. Remember to pin and star my public account to ensure you receive notifications promptly.
4. Recommended Learning Path
1. Beginner: 51+STM32
● Main Learning Content
Understanding the working principles of interrupts, timers, serial ports, NAND FLASH, network controllers, LCD screens, touch screens, etc.
● Recommended Learning Resources
Videos: Wildfire, ZD Atomic
Books: Wildfire, ZD Atomic
● Learning Suggestions
If your future direction is driver development, focus on understanding hardware knowledge in this part of your study. Buy a development board, learn how their examples are written, understand the working principles of commonly used embedded peripheral devices, and how to use C language to program and control these hardware. Learn the basic peripherals thoroughly; while you don’t need to write them all, you must understand the hardware principles.
2. Advanced: ARM+Linux
This part mainly divides into two directions: Linux application development and Linux driver development. I will explain these two directions separately.
With a foundation in microcontrollers, getting started with Linux development will be quicker. You can buy a development board with an ARM-A core; there are many similarities between ARM-A and STM32, making it easier to understand. The biggest difference lies in the development environment, and many beginners are discouraged when setting up the Linux development environment.
Before learning ARM-A, it’s advisable to read ARM Architecture and Programming, which will help you understand the videos by Teacher Wei more quickly, as the difficult parts mentioned in the videos are generally covered in this text.
3. Application Development
● Main Learning Content
Concepts of Linux system calls, implementation of multi-process and multi-threaded development for multitasking, synchronization and mutual exclusion in multitasking: mutexes, semaphores, the process of network data communication, TCP/IP protocol, socket programming, TCP network programming, UDP network programming, QT programming.
● Recommended Learning Resources
Books: Advanced Programming in the UNIX Environment, UNIX Network Programming, Quick Start with Qt Creator
Videos: I haven’t watched any videos on this part; you can search on Bilibili for popular ones.
4. Driver Development
● Main Learning Content
Workflow of Bootloader, compilation, trimming, and porting of UBOOT, compilation, trimming, and porting of the Linux kernel, construction of the root file system, and flashing BootLoader, kernel, and root file system.
Key driver frameworks such as character device drivers, block device drivers, LCD device drivers, touchscreen device drivers, bus device driver models, input subsystem models, etc.
● Recommended Learning Resources
Books: Detailed Development of Linux Device Drivers, Linux Device Driver Programming
Videos: Strongly recommend Teacher Wei Dongshan!!
● Learning Suggestions
As you learn step by step along with the videos, you may find many parts unclear during the first viewing. That’s okay. If, after consulting some materials, you still find it unclear, you can set it aside for now and not delve deeply. Many aspects of the kernel can become very complex once you start to dig deep.
As a beginner, the main focus in learning driver development should be on the driver framework (for example, a commonly used function in the input subsystem model, input_attach_handler(), where initially, you only need to know it is used to match the device and driver software, without needing to understand how this function is implemented internally). Once you have a certain foundation, you can delve deeper into specific points and think about why they are written that way.
5. Experts: Various Complex Drivers
Generally, if you can reach the second stage through self-study, that is already quite good. The complex driver section is usually learned during work. Topics like Android drivers, audio-video drivers, USB drivers, Wi-Fi, Bluetooth protocols, and kernel development are more advanced, and you can become an expert in this field by deeply studying any single topic.
● Recommended Learning Resources
Books: There are many directions in this area, and I am not familiar with all of them. Here are a few good kernel books: Design and Implementation of the Linux Kernel, Understanding the Linux Kernel, Deep Dive into Linux Kernel Architecture.
Videos: Search for Linux Kernel Lectures on Bilibili.
5. Summary
END
Source: Embedded Systems and Linux Matters
→ Follow for More Updates ←