The Internet of Things shows a lot of promise now and for the future with customers, designers and end users having an almost limitless amount of ideas for new products and their implementation.
However, to drive these innovations, one has to choose from the wide range of options available in wireless chipsets, especially when it involves Wi-Fi.
Thanks to its widespread use and availability of a nearly ubiquitous existing network infrastructure, the 802.11 wireless LAN is an attractive technology for building networks of wireless sensors and embedded devices.
This article examines a few chipsets on the market that can be used to add wireless networking to existing embedded designs with relatively low complexity and cost.
The RN131 802.11b/g Wi-Fi module by Roving Networks is a complete low-power embedded networking solution, incorporating a 2.4 GHz radio, processor, TCP/IP stack, real-time clock, crypto accelerator, power management and analogue sensor interfaces into a single, relatively power-efficient module. In the simplest of configurations, the hardware requires only 3.3V power, ground, and a pair of serial UART lines for connection to an existing microcontroller, allowing wireless networking to easily be added to an existing embedded system.
The module incorporates a U.FL connector for connection of an external antenna, without any microwave layout or design needed to use the module. This module has a current consumption of 40mA when awake and receiving, 200mA when actively transmitting, and 4µA when asleep, and the device can wake up, connect to a Wi-Fi network, send data, and return to sleep mode in less than 100 milliseconds. It is possible therefore, to achieve a runtime of years from a pair of standard AA batteries, making it an ideal solution for power-efficient, battery powered wireless sensor networks and Internet-of-Things solutions.
The Texas Instruments CC3000 wireless network processor allows Wi-Fi to be added to any existing microcontroller system relatively easily, and at a low cost. Measuring only 16.3mm x 13.5mm, the CC3000 integrates an entire IPv4 TCP/IP stack, Wi-Fi driver and security supplicant on the chip, making it easily portable for lightweight microcontrollers without the memory burden of implementing a TCP/IP stack in the host microcontroller where relatively low-power, low-cost microcontrollers such as 8-bit AVR or PIC devices are used.
CC3000 reference designs available from TI demonstrate chip-antenna based designs that are already FCC, IC and CE certified, which can make it easier to develop bespoke solutions that can pass compliance testing for products going into markets where such compliance is needed. The CC3000 requires no external crystal or antenna balun, and in fact requires almost no external components at all except for an SPI interface to the host microcontroller and an antenna.
The flexible 2.7-4.8V power supply requirement offers great flexibility when combined with battery power or energy harvesting solutions. Not being a PCB-based module, the chip requires a 50 ohm 2.4 GHz antenna to be added externally; the designer therefore, must have a little familiarity with microwave design, such as microstrip transmission line layout and the choice of the right antenna connector. However, this offers the designer complete flexibility to choose the most appropriate antenna type for the size, range and gain requirements of the design such as a larger external antenna, a compact chip antenna, or a microstrip antenna fabricated on the PCB with no bill-of-materials cost.
The Redpine Signals’ Connect-IO-n series of modules allows 802.11 wireless LAN connectivity to be added relatively easily to an embedded microcontroller system. In collaboration with Atmel these modules have been optimised for use with Atmel microcontrollers, particularly the Atmel AVR XMEGA and AVR UC3 series microcontrollers.
Some modules in this family provide 802.11a/b/g/n Wi-Fi connectivity, while all modules provide the TCP/IP stack on board and are FCC certified, simplifying RF compliance certification of the entire design. These modules are aimed at providing the ability to add 802.11 wireless connectivity to 8-bit and 16-bit microcontrollers with low integration effort and low memory footprint required in the host microcontroller to support the WiFi device, especially where 802.11n support is desired.
The modules in this series can also be interfaced to the host microcontroller over a UART or SPI interface, while a standby current consumption of only a few microamps potentially allows for years of battery life with no external energy source as long as the radio is only briefly enabled when it is needed.
The RedPine RS9110-N-11-28 module from the Connect-IO-n family is relatively unusual in that it provides dual-band 2.4GHz/5GHz 802.11 a/b/g/n connectivity for an embedded device, supporting connection to any Wi-Fi device or network and potentially avoiding congestion in the 2.4 GHz band as used with 802.11b/g devices.
There are plenty of possibilities for low-power connected devices on the open market. Having the right technology partner is advised, if the design team is not too familiar with wireless or Internet connectivity, or there are time constraints, reduced R&D budgets, or need for guidance.
Product manufacturers can partner with LX Group and benefit from their experience with connected devices, embedded and wireless hardware/software design, and ability to transfer ideas from the whiteboard to the white box while covering the entire gamut of testing, standards, compliance or market dynamics abroad.
Clients seeking a reliable implementation can partner with LX Group, which is equipped to create or tailor just about anything from a wireless temperature sensor to a complete Internet-enabled system within the required timeframe and budget.
An award-winning electronics design company based in Sydney, Australia, LX Group specialises in embedded systems design and wireless technologies.