“With the introduction of Zigbee, sensor networks have become increasingly popular. Most Zigbee devices are extremely sensitive to power consumption (thermostats, security sensors, etc.) and their target battery life is measured in “years”. Bluetooth focuses on enabling specific interoperability between cell phones, headsets and PDAs, and is also used as a cable replacement solution for wireless computer peripherals. Most PDAs and high-end cell phones include a Bluetooth solution.
Authors: Ryan, Woodings, Deepak, Sharma
You drive home and press the garage door button – the garage door opens, the main lights in the hallway come on, the central air conditioner is turned on, the plasma TV is tuned to your favorite channel, and your various automatics are in place…though None of this is a reality, but with today’s wireless technology, the realization of the above is by no means a distant dream. When the 802.11 standard emerged in the field of wireless local area networks, a new revolution was quietly underway in the field of cable replacement and sensor networks. The core of these systems consists of a wireless communication device (usually using Bluetooth or WirelessUSB technology), a microcontroller (usually 8-bit), and various onboard external components.
Cable replacement technology
With the introduction of Zigbee, sensor networks have become increasingly popular. Most Zigbee devices are extremely sensitive to power consumption (thermostats, security sensors, etc.) and their target battery life is measured in “years”. Bluetooth focuses on enabling specific interoperability between cell phones, headsets and PDAs, and is also used as a cable replacement solution for wireless computer peripherals. Most PDAs and high-end cell phones include a Bluetooth solution. WirelessUSB does not require a complex networking protocol for simple point-to-point applications. The above three technologies work in the authorized 2.4GHz ISM frequency band, and their advantages include: can be used all over the world, multi-channel plus intelligent coding scheme can provide high bandwidth, using spread spectrum to achieve high interference tolerance and suppression performance, high cost performance .
With the miniaturization and cost reduction of microcontrollers, many external components are being integrated directly into microcontrollers. Currently, 8-bit microcontrollers are available in a variety of package sizes, RAM and ROM capacities, serial communication buses, and analog input and output methods, allowing designers to choose a microcontroller that matches their design requirements and cost constraints . Today, some microcontrollers integrate all relevant, analog and digital peripheral circuits commonly found in microcontrollers and embedded designs. This mixed-signal integration reduces the number of components used, thereby greatly improving system quality and reliability , and significantly reduce material costs.
The right fusion of microcontrollers and wireless communications will ultimately enable designers to significantly reduce development time, component count, and system cost, while improving metrics such as operating distance, power consumption, and latency. Going the “wireless” route can save people huge installation costs, for example if a CO2 detector is placed in an existing building, a wireless solution can be used to complete the installation in days without breaking walls or expensive wiring.
However, you must be careful and ingenious in choosing the right solution. Taking wireless technology as an example, the first decision is to decide what kind of system will be built, whether it is a high-end consumer electronics product (such as a lighting control system) or a low-end commodity (such as a wireless mouse). wireless protocol) to help. Second, the wireless protocol should be as simple as possible to allow for an easy learning curve and an implementation with an appropriate code space.
Choose a microcontroller
The next step is to choose a microcontroller. The first thing to do is to choose a microcontroller with integrated wireless communication circuitry. In addition, there are multiple factors that need to be considered.
(2) Toolbox integration: The ideal model is to make the wireless communication circuit a user module/library, which is expected to simplify the development of wireless communication in the design environment. The designer software development environment should be GUI based with easy click “n” options. It should provide the flexibility to code in C or assembly and use event triggering and multiple breakpoints in the debugging of the design.
(3) Reduced design time: Toolboxes with advanced and higher abstraction levels can be designed at a level that does not require the use of C language or assembly language. This will allow designers to focus on adopting a system to create custom solutions. If the tool can generate data sheets, electrical schematics, and bills of materials, the total design cycle will be reduced from weeks or months to hours!
In addition to separate microcontroller and radio communication chips, discrete multi-chip solutions often require additional external components. This increases the size and cost of the design. By using integrated solutions, designs can achieve extremely small size, lower power consumption and cost, and shorter development time. Figure 1 shows a block diagram of an 8-bit microcontroller with integrated 2.4GHz radio communication circuitry. We note that since the two chips are integrated, the interface between the microcontroller and the radio communication circuit is fully built-in, thereby reducing the number of external pins required, or freeing external pins to Make it a general purpose I/O pin (rather than dedicated to the radio communication interface).
Figure 1 Block diagram of a microcontroller with integrated radio communication circuitry
The integrated solution can take advantage of the tight coupling between the microcontroller and the radio communication circuitry to implement an easy-to-use firmware library for wireless access. Some solutions even offer a complete protocol stack for full bidirectional links between devices. By providing a complete protocol stack tailored to specific radio communication circuits and microcontrollers, these solutions make it easy to establish connections between two or more devices. A simple API is used to interface with radio communication circuits. After the connection is established, the protocol sends the packet to the target device and resends the packet if an error is detected. If the connection to the target device is lost, the protocol will re-establish the connection or find another route to the target device. Figure 2 shows an example of a protocol state machine that handles wireless connection establishment, providing reliable packet delivery and anti-jamming performance without increasing design effort. This enables designers to treat the wireless link as a wired serial bus such as SPI, UART, or I2C.
Figure 2 Protocol state machine example
With the integration of radio communication circuits and microcontrollers, make small temperature sensors that can be placed in each room of the house, and have each sensor periodically report the temperature of its location to the main thermostat (for more accurate room heating and air conditioning control) is a trivial thing these days.
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