"Z-Wave ® Emphasizing ease of use and interoperability, it is one of the cutting-edge wireless network technologies in the application fields of consumer and "smart home". However, it is very challenging for designers to realize the unique ease of use of Z-Wave. Each Z-Wave based device must formally pass the compliance certification before it goes on the market.
These challenges increase the cost and time of application development, but minimizing them is very important for successful design. Unless internal members have rich rf hardware and firmware expertise, it is wise for designers to choose pre certified components and off the shelf solutions. For the design with tight time and budget, there is no margin to study and experiment on RF design. Radio frequency propagation and the coupling between airborne reader and radio frequency card are subtle and too complex.
This paper introduces some basic knowledge of wireless mesh networking, especially Z-Wave. Then, taking silicon labs's 700 series Z-Wave compatible microcontroller chip series and related development tools as examples, this paper shows how to quickly build a certified and available Z-Wave network and apply it to new consumer devices.
What is Z-Wave?
Z-Wave is one of many competing home wireless mesh networking standards (Figure 1). Other standards include ZigBee, thread and insteon. Although Wi Fi and Bluetooth were originally designed without mesh network function, they have been updated for mesh network, and now they have joined the competition in this field, although their power level and data rate are different.
Each wireless network has its advantages and disadvantages, but Z-Wave is designed for low-cost and low-power consumer devices, and continues to develop to meet new needs.
In mesh networks, packets can "jump" from one device on the network to another until they reach the target device. Therefore, the two devices do not have to be within each other's radio range. As long as a device is at least within the radio range of another device on the network, the device can forward the data to the next device in the range, and so on until the data reaches the destination. There may be multiple different paths between any two devices on the network, so the mesh network protocol needs to determine the shortest and most effective path. The more devices connected to the network, the higher the redundancy level, and the more stable the network performance.
Although the concept of network hopping is very simple, it is difficult to realize its practical application. Each Z-Wave device (i.e. node) must be able to communicate with any other node regardless of its manufacturer, function, age, range or firmware version level. As part of a mesh network, nodes must be able to act as intermediaries between starting, target, or other nodes beyond each other. In addition, each node must be able to exchange application level data and commands with any other node. Users may add or delete nodes at any time, and the network must remain stable, operate seamlessly and without interruption. For ease of use, the node must be able to join (and leave) the network without complex user settings, dip switch, service set identifier (SSID) or password, and keyboard, mouse, interface, etc. (if applicable).
Technically, Z-Wave is a low-speed, low-power wireless network with a maximum data rate of 100 Kbps, but the common speed is about 40 Kbps. The typical operating range is about 30 to 40 m, depending on the network RF components, design layout, antenna location, and environmental factors such as wall and environmental interference. Unlike point-to-point networks such as Wi Fi or Bluetooth, Z-Wave is a mesh network. Data packets often jump from one node to another, with a total effective range of hundreds of meters, providing sufficient coverage for home applications.
The operating frequency of Z-Wave is lower than 1 GHz. It is in the industrial, scientific and medical (ISM) band (908.42 MHz in North America and 868.42 MHz in Europe). It is not interfered by Wi Fi or Bluetooth. Although ZigBee can also work in the same ISM frequency band, it still works in the more general 2.4 GHz frequency band in most cases, which is a globally shared frequency band. Therefore, this also means that Z-Wave devices usually do not interfere with other wireless networks.
Zen gecko introduction
The gecko series launched by silicon labs includes a variety of low-cost and low-power microcontrollers. The product family can be further subdivided into several specific application areas, including the "Zen gecko" sub series for Z-Wave development.
The company's Zen gecko series introduces two different Z-Wave devices. One is a "smart modem" chip, and the other is a complete stand-alone module chip. The modem chip (Part No. efr32zg14p231f256gm32-br) is designed to be used with the host processor, while the module (zgm130s037hgn1r) can be used alone without external components.
Both devices are based on 39 MHz arm ® Cortex ®- M4 microcontroller core, although the implementation methods of the two are different. Arm's cortex architecture is a new microcontroller design based on RISC, which is widely supported by software and hardware development tools from hundreds of suppliers.
For the 'zg14 modem chip, the internal cortex-m4 comes with a pre programmed Z-Wave protocol stack. If the processor is not available to users, its existence can be almost ignored by developers. Therefore, although the modem chip can handle the complex Z-Wave protocol, it still needs an external processor to process the application code, which makes' zg14 an ideal choice for relatively complex products, because these products have space and performance requirements to support independent microprocessors or microcontrollers. In addition, just add a 'zg14 smart modem and access the signal and RF components to make the existing products easily compatible with Z-Wave.
On the other hand, the '130s module is a fully self-contained chip and can be used alone as the only microcontroller in the product. The internal cortex-m4 of the device is available to developers and can be used for application code. Compared with the 'zg14 smart modem,' 130s module has larger size but more powerful functions, including analog-to-digital converter (ADC) and digital to analog converter (DAC), analog comparator, capacitance detection interface (for touch screen), counter, timer, watchdog timer and UART. The module only needs to be connected to power supply, grounding and antenna to realize a fully functional Z-Wave controller.
These two devices together constitute the 700 series, the latest Z-Wave component of silicon labs, which conforms to the latest Z-Wave specification. Specifically, both devices support the latest security function (security-2, or S2) and the optional function smartstart to simplify user settings. In addition, all three Z-Wave data rates (9.6, 40 and 100 kbps) and all global bands are supported. Like all Z-Wave devices, these two devices are backward compatible with all lower versions of Z-Wave devices and controllers.
Users who have previously used silicon labs 8051 based Z-Wave devices ("500 Series") may want to migrate some or all of their existing code to the new version of arm based devices. To solve this problem, silicon labs provides software libraries and "building blocks" to simplify transformation. Although the old version of 8051 code can not be converted to the new version of arm code simply by recompiling, the code base should be able to provide great help.
Internal structure of efr32zg14 Z-Wave chip
Efr32zg14 is an intelligent modem system on chip (SOC) with simple concept (Figure 2). The device includes a two-wire serial interface for connecting external host processor and an internal arm cortex-m4 MCU core for processing Z-Wave protocol stack. The radio part contains almost all components required for physical radio.
During operation, the 'zg14 communicates with the host processor only through the UART interface, and the baud rate can be up to 115200 BD. Only two signal lines need to be connected for receiving and transmitting respectively. The host processor sends commands and data through the UART interface for 'zg14 response. Resetn is the third signal line for 'zg14 reset and can be easily driven by any I / O pin of the host processor.
'only three digital signal lines need to be connected between the zg14 and the host processor, four digital signals with the simple IPD (integrated passive device), and then connected to the crystal oscillator and several simple analog components (Fig. 3).
Alternatively, the designer can choose to connect a low-level valid suspend signal, which can put 'zg14 in a low-power state and interrupt all radio communications. In fact, 'zg14 may be suspended most of the time to save energy, depending on the expected application.
In addition, developers can also choose to connect the internal flash memory of the chip through three core wires to reprogram the 'zg14 firmware in real time. Silicon labs provides such binary firmware. As mentioned earlier, 'zg14 firmware cannot be used for user code.
As shown in Figure 3, designers can choose to use surface acoustic wave (SAW) filters, depending on the geographical location where the final product is deployed: SAW filters are required in some parts of the world and not in others. In addition, designers can also choose to be equipped with saw filter banks and configure them in real time through the two output pins saw0 and saw1 of 'zg14, so as to make the final product applicable to any region and simplify design, manufacturing and inventory.
Internal structure of zgm130s Z-Wave module
Compared with the 'zg14 modem SOC,' 130s module has more complex structure and more powerful functions. Silicon labs calls it system level packaging (SIP). From name to reality, the '130s essentially integrates multiple chips, so it can be used as an independent microcontroller and Z-Wave controller (Figure 4).
The arm cortex-m4 CPU core of the module runs at 39 MHz, with 512 KB flash memory and 64 kb SRAM. Since the Z-Wave protocol stack has been included in the transceiver module of the module (upper left corner of the block diagram), the user can use most of the storage space. In fact, the module is equivalent to 'zg14 smart modem chip.
The '130s contains independent internal DC / DC voltage regulators and internal crystal oscillators, so no external clock elements are required. In addition, the module also has several analog and digital peripherals, including ADC and DAC, temperature sensor, two analog comparators, three operational amplifiers, capacitance detection interface, DMA controller, 32 general-purpose I / O pins, etc. " The 130s is packaged in lga64 and is limited by pins. Not all I / O pins are available at any time, depending on the software configuration.
Although the '130s is packaged in a 64 pin package, the external connection is very simple. As shown in figures 5 and 6, the device only needs to connect a simple bypass capacitor (for power supply / grounding) and connect the antenna through a single line, and the other pins can be used for user I / O.
Start with the starter kit
Start Z-Wave development with Zen gecko series. The easiest way is to use Z-Wave 700 starter kit. All components of the kit are equipped in pairs to form the smallest two node network: two mainboards, two wireless boards, two expansion boards with switches and LEDs, two flexible antennas and two USB cables. In addition, there are two USB dongles that can be used with personal computers: one with Z-Wave radio sniffer application (zniffer) and the other with Z-Wave controller function. The hardware and accompanying software support all Z-Wave options and protocols in all regions of the world.
Figure 7 shows a group of circuit boards, with a radio board on the top and an expansion board on the right. The main board does not include zgm130s sip, which is installed on the radio board. On the contrary, the most significant feature of the motherboard is the bitmap LCD, which is very useful for debugging or GUI development.
Software installation
Simplicity studio is an integrated development environment (IDE) launched by silicon labs, which can be used for the company's Zen gecko and other microcontrollers, and supports windows, MacOS and Linux systems.
When installing simplicity studio, if you connect a motherboard (no matter which one) in the development kit to the development system, the installation and configuration process will be simpler. The IDE will detect the hardware and automatically load the necessary software support.
If the hardware is not available, you can manually perform the following configuration:
After running simplicity studio, click the green arrow in the upper right corner (Figure 8).
Simplicity Studio provides two options: "install by device" or "install by product group" (Figure 9). The final results of the two options are the same, but it is easier to choose the former, so click the large green button "install by device".
If the development board is installed, simplicity studio should automatically detect the hardware, but if not, it is also easy to manually find the required software package. Just type "" 6050a "" (short for the full name of the development kit) in the search box, as shown in Figure 10. Double click the indicated software support package and click next.
Next, simple
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