NuMicro® M2351 applications – Short-range wireless communication module, 802.15.4 thread module

[NuvotonMarcom]

Nuvoton Microcontroller Application Business Group Technology Manager – Robert Ling

What is 802.15.4 Thread?
First, let’s take a look at which are the mainstream communication standards of the Internet of Things (IoT).

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According to the figure above, we can see that the communication methods of IoT are divided into two major categories long-range wireless and short-range wireless; and these two major standards include many detailed standards that need to be discussed. Let’s take a look at the explanations in the next table to learn about some factors that need to be considered when these different standards are used.

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*1: Low-Power Wide-Area Network Range > 1km, for example, LoRA, SigFox, NB-IoT
*2: Short Range < 100m, for example, ZigBee, Thread, Z-Wave or Bluetooth

From the table above we can clearly understand that wireless communication needed for terminal devices with sensors to collect data is more of a short-range solution, so we think that providing a set of short-range reference design module that is easy to develop and equipped with data communication security consideration features will be very helpful to the industry. Among the many standards that comply with the IEEE 802.15.4 standard, such as ZigBee Pro, Thread and RF4CE, we discovered that the development of Thread has the most potential. The reasons for this include the following: (1) Supported by major companies such as Google, Arm, and Samsung; Apple also joined the Thread faction in 2018. (2) IP-based protocols can be easily integrated with software communication protocols. (3) Devices that are highly standardized, highly interoperable, highly secure and suitable to use the battery to supply power. The figure below is the forecast statistics for market development.

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From the figure above, we can see that applications based on IEEE 802.15.4-based protocols are expected to grow, and mainly centered on ZigBee and Thread; Thread in particular. In terms of application, based on the market research data, Smart Home, Medical Devices, Auto Metering, Smart Building, and Industrial are the main application fields.

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Thread reference design for NuMicro® M2351
We and the company Cascode located in Great Britain collaborated and released a transceiver reference design for a microcontroller plus 802.15.4 that includes the MAC (Media Access Control) layer. Since M2351 can provide TrustZone® as well as XOM functions, the communication protocol layer can be placed in the secure world or XOM (eXecute-Only memory) based on the program development plan; and since Cascoda’s transceiver ICs (CA8210, CA8211) all include pre-processing of the MAC layer (ROM-based MAC firmware and MAC Co-processor), so M2351 is more than capable for being responsible for post-processing of the MAC layer and processing its upper IP layer and above, including the application layer. The inclusion of MAC pre-processing (Low-MAC Transceiver) provides the following benefits:
1. The API of the communication protocol is not affected by the timing as much; it has fast response times and complies with the standard more.
2. Smaller dependence on specific microcontrollers and OS.
3. Mutual pure-software processing of the MAC layer has fewer risks; the protocols cannot be easily tampered with and are safer.
We organized the application architectural diagram as shown below:

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The architectural diagram described above can achieve approximately 3 times increase in wireless transmission power improvement (about 5dB) based on Cascoda’s innovative patent for wireless transceivers (U.S.A., China, Taiwan, and South Korea), doubling the transceiving distance compared to average solutions while having super low-power consumption performances. In other words, it allows devices that use batteries to have longer battery usage time. Moreover, additional microcontroller dedicated to processing wireless communication protocols is not needed; the two main chips included in the overall reference design module can fully handle the design requirements for communication and terminal products. For example, wireless meter reading, remote monitoring, smart home, smart factory, smart building, and other IoT applications.

Detailed features and market opportunities brought by Nuvoton’s 802.15.4 Thread reference design.
Here, we also included the following schematic description for the Thread communication protocol (Thread Stack) run on M2351:

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From the figure above we can see that the Cascoda Company developed ROM code based on hardware MAC to support Open Thread protocol; Nuvoton also ported this protocol onto M2351 based on Open Thread. Since there is sufficient resource, M2351 can also run upper layer applications or even RTOS; place these upper layer applications or RTOS into the non-secure world of Trusts® to fully utilize the features of Armv8-M to achieve software security for networked applications. Such a solution can bring the following market opportunities:
(A) It is a high performance wireless transceiving invention. The doubled reception distance solved the stability issue of service scope.
(B) Complies with standard reference design platforms. Fully compatible with existing 802.15.4 Thread standards; the Open Thread Stack reference design provided for free by Cascoda and Nuvoton makes it convenient for communication software protocol developers to perform the integration.
(C) Wide coverage of communication/monitoring areas with low power consumption.
(D) Quickly keep up with mainstream applications on the market. 802.15.4 already exists on Comcast, Amazon Echo+ and Google NEST; Cascoda and Nuvoton provide an open and universal platform that is very convenient for the development and design for products that require short-range communication. It is an innovative, secure and high performance 802.15.4 Thread terminal product reference design example.