Wireless Buying Guide

When it comes to throwing data over the ether, there are a lot of options. If you're confused about what wireless technology is best for your next project then keep on reading. Hopefully our entirely biased view will steer you toward the wireless module of your dreams (or at least your design requirements).

Bluetooth

While Bluetooth is rarely the less expensive option, it does carry the advantage of being fairly universal. There is an ever-growing number of Bluetooth enabled devices on the market and almost all of them are capable of communicating with each other. The Serial Port Profile (SPP) is a Bluetooth profile for piping serial data from one Bluetooth device to another and works really well. Bluetooth modules that support audio are one of the easier ways to transmit audio signals wirelessly. Keep in mind, however, that Bluetooth can be a power hungry technology. Also, it's pretty much limited to point-to-point networking.

Nordic

Nordic radio modules are a very flexible solution for near-field wireless data transmission. They're the go-to wireless device for low-power applications and can "sleep" in the micro-amps. Not to mention that they're one of the less expensive RF solutions so if you just need to get a small amount of data from one point to another, this is the way to do it. Don't forget, though, Nordic modules are low power and high-frequency which limits their range to near-field applications and you'll need to write your own communication protocol to do things like multi-point networks, encryption or checksums.

WiFi

WiFi is awesome because it's all over the place. Being such a common standard, unless you're in the middle of nowhere, you can probably access a WiFi router and hop onto the internet. Also, because they communicate with WiFi routers and access points, the range of your communication is only limited by the range of the network whether it's a WAN or the entire internet. WiFi is great for moving larger amounts of data (1Mb+) and can do so quickly. It does take more power to do all the cool stuff that WiFi does, so it isn't the right way to go for power savings. Also, it's a little bulkier than some other options, not only physically but control-wise.

¹ Because Wi-Fi is usually used to access the internet through a wireless router, no point-to-point range is listed.

RF Modem

These long-range 433MHz modems are super handy when you just need to open up a long distance pipe for serial data. All of the buffering, error detection, etc. is wrapped up and handled by the modem so all your system needs to be able to do is send or receive serial data. Just power them up and whatever serial character enters the Tx pin on one unit shows up on the other unit's Rx pin. They aren't cheap, however, and the unit and antenna together is a tad bulky compared to other devices.

Synapse

Synapse modules are smart radio modules similar to the XBee except that they run the the award-winning Synapse SNAP network operating system. The embedded Python virtual machine makes application programming fast and easy and you can send your code to the module over the air. That's right, the synapse modules can be programmed with a stripped-down Python style language and execute code on it's own, no separate microcontroller required! You do pay for the extra processing power, though, so if you just need to send a few bits point-to-point the Synapse stuff may not be right for you.

General RF

This is a sort of catch-all category for RF transmitters and receivers that don't necessarily fit into our other categories. RF Link devices are the most bare bones radio communication device that we carry, they're also the cheapest. Because they're cheap, they don't come with any frills, so they can be a little more complicated to use although they're common enough that example code is fairly easy to come across. Also, we sell the receivers and transmitters as separate devices and you'll need both to make a complete one-way link. The RFM devices are also inexpensive but they're a little smarter, they're also sold as single unit transceivers capable of both sending and receiving data. Example code is readily available for these as well, there's even an Arduino Shield for the RFM22. The Wixel is a bit of an outlier in this category, it's certainly the 'smartest'. The Wixel is essentially a development board for TI's  CC2511F32 microcontroller which is capable of acting as a serial relay, an I/O tunnel, or as a stand-alone controller.

Cellular

Cellular technology is the ultimate in compatibility and coverage. There are cellular networks covering more than 80% of the world's population making it a nearly ubiquitous technology. Depending on the type of cellular network, you can push fairly large amounts of data continuously over the network. Though, data doesn't have to stay within the cellular network and can usually be sent straight on to the internet. For all this versatility, there is a price to be paid. Cellular networks require a subscription service that make them more expensive than WiFi or other wireless networking alternatives, but when your device is in South America and you're in Europe getting data from it... it's worth every penny. Beware though, cellular networks may cover large portions of the globe but they're not everywhere, there are also concerns about reliability depending on how far afield your device is. Cellular modules are also bulky when compared to other radio network devices and consume significantly more power.

Glossary of Terms

Range: The range of a wireless device is affected by several factors including the transmit power of the device, the type of antenna connected and the surrounding obstacles or conditions. The range listed here reflects the maximum range of the device in ideal conditions and in open air, line-of-sight. Expect this distance to be smaller if you're trying to communicate indoors or through walls, trees or other barriers.

Power Consumption: This represents the amount of power that the device will typically consume during transmission, your system should be capable of sourcing at least this much current and then some to avoid erratic behavior or brown-out conditions.

Frequency: The operating frequency of the device will affect its range and penetrative force as well as its tendency for interference. Lower frequencies require larger antennas to be effective but they also have greater penetrating power when it comes to transmitting through walls and barriers.

Tx Power: The Tx (Transmit) Power is the amount of power that the device actually broadcasts. While this is closely tied to range, it isn't the only factor. This number is important to keep in mind when selecting an antenna for a device to ensure that you comply with your local radio communication laws. The power listed on this chart is the maximum output power and it can be adjusted in firmware in case you need to dial it back.

Data Rate: The speed at which the device can communicate over the air will effect not only how much data you can push over the network at once, but also how reliably the device will communicate at long distance. Slower transmission rates can be beneficial if your network spans a large distance, a fact exploited by the XSC line of devices. The speeds listed here are maximums and can be adjusted in firmware for several of these devices.

Antenna: The type of antenna, if any, that the module comes equipped with. There are several things to keep in mind when it comes to selecting the proper antenna or antenna connector for your project. A chip antenna is small and easy to enclose, but it doesn't give the best gain. A wire antenna is simple and effective but it's also not as small as the chip antenna and can be more difficult to incorporate into your design. If you're building your wireless device into an enclosure it can be beneficial to attach an external antenna, this can be achieved either by U.FL or RPSMA connection. U.FL is the type of connector often found on the wireless adapters in laptop computers and other small devices, routers and larger devices often have RPSMA connectors. Remember that whenever you add an external antenna to a device you change the gain of the transmitter, so be sure you stay in compliance with your local radio communication regulations.