How to build a RISC-V MCU ecosystem?

How to build a RISC-V MCU ecosystem?

In 2021, the global microcontroller (MCU) market has total sales of 19 billion U.S. dollars, with shipments exceeding 25 billion. From 2021 to 2028, the compound annual growth rate of MCU is about 10%, and it will increase to 36 billion U.S. dollars by 2028. According to a report released by IC Insights in August 2021, automotive MCUs account for 40% of the global MCU market. It is estimated that automotive MCU sales in 2021 will reach 7.6 billion U.S. dollars, an increase of 23% compared to last year, of which about 77% are 32-bit MCUs.

In addition to the automotive market, the second largest market for MCUs is industrial applications (accounting for 30%), and the remaining 30% is mainly used in consumer electronics/home appliances, Internet of Things, smart cards, and computers and communication networks.

MCU ecology based on Arm Cortex

32-bit MCUs basically use Arm Cortex-M series microprocessor cores. Major MCU manufacturers include: ST, Renesas, Infineon, NXP and Microchip. The Cortex-M processor series is based on the Arm M-Profile architecture, designed for embedded systems, and has the advantages of low latency and high deterministic operation. This series of processors has models with different performance specifications, including M0, M0+, M1, M23, M3, M4, M33, M35P, M55 and M7, which can meet the needs of microprocessor chips with different performance, power consumption and cost.

The MCU ecology based on the Arm core has been relatively mature after years of development. Around the Cortex-M core, Arm provides a variety of tools for MCU developers from development environment to software. For example, the integrated development environment includes Arm Keil MDK and Arm Development Studio; the compiler includes Arm Compiler 6, GCC; the software includes Cortex Microcontroller Software Interface Standard (CMSIS), Trusted Firmware-M (TF-M); the operating system includes Mbed OS, Keil RTX5; debugging tools and development boards have JTAG and SWD debugging hardware. In addition, there are many third-party software and development tool chains to choose from, such as compilers, debuggers, RTOS, and software libraries.

In order to enhance market leadership, leading MCU manufacturers are also actively building an ecosystem with their own MCU chips as the core. The STM32 MCU ecosystem is a typical example. As the leader of Arm Cortex 32-bit MCUs and MPUs, ST not only depicts and builds a complete STM32 MCU chip development circuit diagram, but also provides customers and developers with a complete learning, development, testing and evaluation environment.

The STM32 MCU ecosystem also brings together many third-party development tools and partners, including the world’s major cloud access platforms; supports mainstream RTOS in the Chinese market, such as OneOS, TencentOS Tiny and RT-Thread; hardware development tools include various development boards and Debugging and burning tools; software development tools include RT-Thread Studio, etc.

RISC-V and MCU

Originating from the University of California-Berkeley, RISC-V has caused a lot of disturbance in the global open source hardware community in recent years. Universities, research institutions, chip manufacturers, and Internet giants have adopted and supported this instruction set that is promising to compete with Arm. Architecture (ISA). China has tried for many years on the road of independent and controllable microprocessor development, but it is still subject to international mainstream architectures such as X86, MIPS and Arm. RISC-V has ignited new hopes for domestic CPUs.

RISC-V has now received global support and active participation. In addition to the RISC-V International Foundation, which is responsible for the promotion of RISC-V, there are many industry organizations dedicated to promoting RISC-V and open source hardware in China alone. Including China RISC-V Industry Alliance, China Open Command Ecosystem (RISC-V) Alliance, and Taiwan RISC-V Industry Alliance. Global vendors that support RISC-V include Intel, Google, Nvidia, Western Digital, Qualcomm, NXP, Huawei, Ali, ZTE, and Unigroup Zhanrui.

Currently, manufacturers focusing on the development of RISC-V core IP include SiFive, Saifang Technology, Xinlai Technology, Alibaba, and Andes Technology. The RISC-V core IP provided by these IP vendors are open source, commercial, and developed for their own chips. From the application of RISC-V chips, RISC-V can be seen from high-performance computing processors with up to 1000 cores to ultra-low power single-transmit/two-stage pipeline microprocessors. In terms of the application and development of RISC-V in the microcontroller (MCU) market, many domestic MCU manufacturers have developed MCU chips based on the RISC-V core. RISC-V MCU developers include Zhaoyi Innovation, Qinhengwei, Espressif Technology, Boliu Intelligent, Telink Microelectronics, Zhongwei Semiconductor and Hangshun, etc.

In MCU design, what are the advantages and disadvantages of the RISC-V core compared with Arm? According to Nanjing Qinheng Microelectronics, after decades of development, Arm has become more mature, but its CPU architecture has become extremely complex. This can be seen from the complexity of its architecture documents and the number of instructions. There are also patents and Issues such as the high cost of architecture authorization. RISC-V is positioned as a completely open source, simple structure, and modular design, which greatly facilitates customers to freely customize according to their own needs (from the beginning, it has avoided the problems that existed in the development of Arm for decades). However, the development time of RISC-V is still relatively short, and the ecological elements such as compilers and development tools are still developing, unlike the Arm ecosystem which has been relatively mature.

RT-Thread developers also agree with the many advantages of RISC-V, and especially emphasize the value of RISC-V to MCUs. Using the RISC-V instruction set to design the MCU allows chip manufacturers/developers to quickly complete low-threshold, low-cost chip design, and can be customized for specific application scenarios, with strong flexibility. However, RISC-V related compiler, tool chain, IDE, OS support, etc. are not yet complete. In addition, as more and more companies use RISC-V architecture to customize chips, the fragmentation problem has become more prominent.

How to build a RISC-V MCU ecosystem?

If RISC-V wants to gain a foothold in the USD 20 billion MCU market, it must establish a healthy MCU ecology. There are many challenges in building a RISC-V MCU ecosystem, which are briefly listed as follows:

RISC-V processor cores are mixed: open source, commercial, self-developed RISC-V cores are available, and it is difficult to form a unified ecosystem like Arm;

The trade-off between RISC-V and Arm core: Most of the existing MCU manufacturers choose to develop and support both Arm and RISC-V MCUs, and it may be difficult for RISC-V to obtain sufficient resource support in the general-purpose MCU market;

Software and development tools: Compared with the Arm ecosystem, it is still not perfect, and the functions, performance and ease of use need to be improved;

Developer community: training tutorials, offline and online exchange meetings, development boards and application solutions all require resource investment and continuous maintenance;

New model of open source hardware: Unlike open source software (such as Linux), open source hardware requires chip design and tape-out costs, and the profit model is not yet clear.

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