What’s the best way to give a device a wireless connection? The answer is “It depends.” It depends on the device’s purpose, what it needs to connect to, the data rates and volumes it needs to support, the power budget, the radio frequency (RF) environment, the intended price, and many other factors.
One way of narrowing the options is to look at where the most popular wireless protocols came from, as a way of understanding the appropriate ways of applying them in your design.
Take the near-ubiquitous Wi-Fi, developed to extend the popular wired IEEE 802.3 Ethernet standard beyond the reach of thick Cat5 cables and RJ45 connectors to a more elegant wireless physical interface. Because of its wired-network heritage, Wi-Fi is a relatively complex and power-hungry way of implementing a wireless interface. Wi-Fi chips and modules often integrate support for the Transmission Control Protocol (TCP)/Internet Protocol (IP) stack that enables Internet connectivity, but this integration means having to run relatively complex software. This in turn has implications on the cost and power consumption of the implementation. Wi-Fi based networks also tend to have a star topology, with an access point acting as the Internet gateway for multiple devices.
Bluetooth, on the other hand, was developed as a “wireless wire” or common wireless approach, serving to replace multiple “wired connection” standards in use in the early days of mobile telephony. (Interestingly, the Wireless Universal Serial Bus (WUSB) attempted to do something similar for the now-ubiquitous USB connector, but despite hundreds of millions of dollars of investment somehow it didn’t take off.) Because of its heritage, Bluetooth implementations tend to use less energy than Wi-Fi connections, transmit data more slowly, and have a shorter reach. And they establish peer-to-peer or mesh network topologies, rather than the star topologies of Wi-Fi.
For many Internet of Things (IoT) device designers, power consumption is the governing factor in the choice of which wireless interface to use. Wi-Fi normally loses out here, because common implementations can consume up to 300mA during an active data transfer compared with Bluetooth’s 3mA, and it consumes 1mA in an idle state compared with Bluetooth’s 50nA. If you’re trying to build devices that can run for a decade on a coin cell (think door-closure sensors, for example), then these figures will effectively make the choice for you. Bluetooth has also evolved steadily since its introduction with updates, such as Bluetooth Low Energy (BLE) that significantly reduces power consumption, which successfully enables new applications like fitness monitors, toys, and remote sensing.
The other important issue designers face when choosing a wireless standard is the “make versus buy” question: That is, is the implementation style of the wireless interface going to define your design’s differentiating value, or is it enough to simply have a wireless interface? If it’s the latter, then designers can relieve themselves from a great deal of complex RF engineering, printed circuit board (PCB) design, firmware development and validation, and certification challenges by simply buying a packaged solution. Of course, these may appear costlier than a do-it-yourself (DIY) approach, but they are likely to reduce the design’s time-to-market substantially, enabling your design to steal a march on its competitors and therefore reach volume pricing more quickly than would otherwise be possible.
One practical way to explore your options is to find a supplier that produces a range of Wi-Fi and/or Bluetooth modules in similar footprints. Panasonic can help here, offering a Wi-Fi module and a module series that integrates both Wi-Fi and Bluetooth.
The Panasonic PAN9420 Embedded Wi-Fi Module supports the 802.11 b/g/n Wi-Fi standard at 2.4GHz. It has an onboard central processing unit (CPU) to run a full network IP stack along with a Web server, internal static-random-access memory (SRAM), and in-system programmable flash memory (Figure 1). The module supports both access-point and infrastructure modes concurrently, to make it easy to set-up simultaneous Wi-Fi connections to smart devices and home network routers. The firmware also supports client, micro-access-point, and ad-hoc mode applications. It can also receive updates over-the-air, a vitally important feature for IoT devices.
Figure 1: The Panasonic PAN9420 Wi-Fi module has an onboard CPU to run a full network stack. (Source: Panasonic)
For more sophisticated applications, Panasonic offers the PAN9026 Wi-Fi and Bluetooth Radio Modules (Figure 2). These modules run 802.11 a/b/g/n Wi-Fi at both 2.4GHz and 5GHz as well as the Bluetooth and BLE protocols. The modules’ capabilities empower designers to build hybrid devices that include both Wi-Fi and Bluetooth connectivity. This allows use cases such as Wi-Fi access points that can also provide Internet access to a network of low-cost BLE devices that are connected to each other in a meshed network. Furthermore, these modules also have a “coexistence interface” to enable arbitration between multiple co-located Wi-Fi networks, Bluetooth, and/or a mobile network such as Long-Term Evolution (LTE), all this implying that the modules can be useful with even-more flexible connectivity solutions.
Figure 2: PAN9026 Wi-Fi and Bluetooth radio modules can act as a bridge between devices running on different wireless interfaces. (Source: Panasonic)
Both the PAN9420 and PAN9026 modules come with support. The PAN9420 evaluation kit includes a PAN9420 host board, with two USB to Universal Asynchronous Receiver/Transmitter (UART) converters, and a PAN9420 target board, with a PAN9420 Wi-Fi module. The module itself is loaded with example firmware for IoT applications and serving Web content.
The PAN9026 evaluation kit includes a micro Secure Digital (SD) adapter, a Cortex A9 microcontroller, and a micro SD card, with a Yocto Linux XFCE desktop environment image. There’s also a power cable that adapts a USB-A connector to a 5.5/2.5mm plug.
At the beginning of this discussion we asked, “What’s the best way to give a device a wireless connection?” The answer may still be “It depends,” but the availability of embedded modules, like those outlined in this article, at least makes exploring the options much easier. It may also mean that in some circumstances you don’t have to choose one or the other, because you can have both.
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