2.4GHz ZigBee Wireless Network Coordinator CC2531USB-RD

# Abstract The CC2531USB-RD provides a PC interface to 802.15.4 / ZigBee applications. The dongle can be plugged directly into your PC and can be used as an IEEE 802.15.4 packet sniffer or for other purposes. With the CC2531 USB Firmware Library available on the web you can develop your own software to utilize this part. To program the dongle, an external programmer (e.g. the CC debugger or SmartRF05EB) is required. This is not included in the kit. The USB dongle can be used as a reference module for prototyping of USB devices and for testing the RF performance of CC2531 with a small size whip antenna. - 3D models of body parts, as well as device assembly: [https://grabcad.com/library/2-4ghz-zigbee-wireless-network-coordinator-cc2531usb-rd-with-stand-1](https://grabcad.com/library/2-4ghz-zigbee-wireless-network-coordinator-cc2531usb-rd-with-stand-1) - Flashing the CC2531 USB stick: [https://www.zigbee2mqtt.io/guide/adapters/flashing/flashing_the_cc2531.html](https://www.zigbee2mqtt.io/guide/adapters/flashing/flashing_the_cc2531.html) - This project is based on the CC2531 USB Dongle Reference Design (reverse engineering performed): [https://www.ti.com/tool/CC2531USB-RD](https://www.ti.com/tool/CC2531USB-RD)  ## Features - CC2531 USB Firmware Library and Examples (downloadable from web) - RemoTI, TIMAC and Z-Stack for CC2530 - SmartRF® Studio, Packet Sniffer and Flash Programmer # Theory ## Relevance Currently, wirelessly controlled devices connected to systems, the so-called "Internet of Things", are becoming widespread. An increasing number of "Internet of Things" devices are created for the consumer market segment, including home automation or "smart home". "Smart home" can be based on a platform or concentrators that control intelligent devices and appliances. The concentrator is sometimes also called a hub, gateway or coordinator. The most common standard for wireless connection between devices and the "smart home" coordinator is the ZigBee protocol. To control devices in the network, a coordinator from the same manufacturer as the end devices is usually used. This creates some inconveniences. For example, you cannot use devices from different manufacturers in the same network. In them, control, setting parameters and operating scenarios is not always convenient and implemented in detail. This device will simplify the control of sensors, as well as use devices from different manufacturers in the same network.  *IoT Map* ## Proposed solution The physical part of the solution consists of sensors and smart home devices from various manufacturers, as well as a developed coordinator. The server or software part of the solution combines: ZigBee2MQTT bridge, with which it is possible to control ZigBee devices via an MQTT broker. Message Queuing Telemetry Transport (MQTT) is a simplified network protocol that runs on top of the Transmission Control Protocol (TCP). TCP is one of the main protocols for transmitting data on the Internet. MQTT is focused on exchanging messages between devices on the publisher-subscriber principle. The broker is the central MQTT node that ensures interaction between clients. Data exchange between clients occurs only through the broker. Home automation is the direct configuration and execution of scenarios and algorithms for the operation of smart home devices. To organize the operation of the entire scheme, you must use your own server (for example, a home computer or miniPC), to which the coordinator is connected.  *Architecture* ## More about the ZigBee network protocol ZigBee is a wireless network similar in its operating principle to Wi-Fi or Bluetooth. It differs from the above-mentioned networks, first of all, in its high energy efficiency - devices can operate on one battery for a year or more. There are three types of devices in the ZigBee network: - coordinator - the main network device, without which the user cannot interact with the end devices; - router - an auxiliary device that allows data to be transmitted from end devices to the coordinator. Almost any end device powered by a constant power source can act as a router; - end device - the sensors themselves, or actuators. If the device is powered by batteries, then most of the time it is in sleep mode, due to which high energy efficiency is achieved. A network operating on the ZigBee protocol uses a more advanced "Mesh" topology. In it, if one connection is broken, a bypass route will be laid, and the signal will reach the recipient along a new path. This is possible because there is a direct connection between the network nodes, and not just a connection with the "center". It is much more reliable and is used, for example, in the Internet itself.  *Network topology types* --- # Software Below is a graphical visualization of the smart home network as a map in the [ZigBee2MQTT](https://www.zigbee2mqtt.io/) control panel. The star in the center is the coordinator. The repeater devices and sensors are shown in the form of pictures of devices and red logos. The network address is signed in the form of text next to each device. To connect your sensors to the coordinator in ZigBee2MQTT, you need to go to the service web page and add each device separately.  *Real Network map* ___ # Hardware The coordinator circuit is implemented on the basis of the CC2531 system on a crystal with USB and ZigBee support for a frequency of 2.4 GHz. Allows you to create devices or network nodes with the ability to update via USB with minimal material costs, has a built-in programmable flash memory of 256 KB and 8 KB of RAM. A low-power linear regulator with a low voltage drop (LDO) is installed to power the chip. It generates a voltage of 3.3 V from 5 volts of the USB bus. The circuit also includes connectors: USB A, a 10-pin debug connector, and a high-frequency connector for connecting an external antenna. A balun is installed in the antenna circuit, it converts an electrical signal from symmetrical to asymmetrical and vice versa. The circuit also includes two programmable buttons and two LEDs. ## PCB A four-layer printed circuit board is used. Some of its features: - The SMA antenna connector is mounted horizontally on the end of the board using surface mounting. - Near the CC2531 microcontroller, the QFN-40 case has 8 “test point” holes for factory firmware. - To connect the shielding polygons in the high-frequency part of the PCB, metallized vias are made near the antenna. - The width of the printed conductor for connecting to the antenna is matched with an impedance of 50 Ohms. ## Case It is made in a case made of black ABS plastic. In SolidWorks Plastics, the injection molding of the case base and cover is simulated. In the animations, the colors from blue to red show the melt temperature of the material when pouring the mold.  *CC2531USB-RD Module Assy*  *Top case*  *Bot case* ## Stand "Puck" For convenient installation on flat surfaces, a stand with a USB extension cable was developed for the coordinator. It is used in the kit and allows the user not to bother with finding a place to install the device. It can also be used to connect other peripheral devices.  *Puck* --- # Result The completed view of the coordinator. The case consists of a cover and a base and has no mounting holes. The connection between the cover and the base is made in the form of plastic latches. The shape of the case parts is oriented towards injection molding. For convenient installation on flat surfaces, a stand with a USB extension cable was developed for the coordinator. It allows the user not to bother with finding a place to install the device. It can also be used to connect other peripheral devices. * The assembly drawing of the device is in the file CC2531USB-RD_v1_ASSY.PDF. * The electrical connection diagram is in the file CC2531USB-RD_v1_CONN.PDF.