ZigBee & Z-Wave

‘Home Area Network’ Radios

Now we’re getting into set-ups where you have to run your own network. Remember, with Ethernet, WiFi, Cellular, and Satellite you’ve got an existing network you’re joining as a client, and with BTLE your phone or computer can act as the network manager.

ZigBee and Z-Wave (as well as ‘similar’ low power radios such as XBees) are often used for home or office-scale networks and automation. These are low power radios, so great for battery usage. But more importantly, they are usable in mesh and high-density point-multipoint or multipoint-multipoint networks - something BTLE does not yet do very well.

These two transports, despite both starting with Z and both used for home/industrial automation, have nothing to do with each other.

ZigBee

ZigBee/802.15.4 is available in both ~900MHz and  2.4GHz. You’ll see it most often as 2.4GHz though, so it shares the same frequencies as WiFi/BT. Zigbee and is a freely available standard with dozens of chips available and a flexible protocols. You can use an existing ‘profile’ like the ZLL (Zigbee Light Link) or just make your own.

For example, here's a slide from the ZigBee Alliance presentation on Zigbee Light Link showing the defined protocol for a lamp and switch to 'pair'. It's complicated, sure, but it's well defined and interoperable.

Gateways

ZigBee is cheap, cheaper than WiFi, but to connect it to the Internet you’ll need a gateway.

So, for example, Phillips Hue bulbs have a ZigBee chipset (The ATSAMR21 series of chip) inside that does both the radio and LED control.

 

They could have gone with WiFi or Bluetooth in each bulb but it would have greatly increased the cost and complexity. When you need it to be, well, as cheap as a light bulb, ZigBee radio’s $1-per-chip radio probably helped a lot.

All the lightbulbs talk to a gateway bridge/hub which as both Zigbee and WiFi or Ethernet. All of the switches and controls all talk to the same hub. That hub then connects to the internet or just is used from within the home without external access.

 

Slide from Philips' technical presentation

Z-Wave

Z-Wave is a more constrained-use protocol, its design for home use and to make equivalent devices you have to buy chips from the single-supplier. It’s a 900 MHz standard so you get a little more range than 2.4GHz ZigBee. especially in an industrial or urban environment since Sub-1GHz penetrates brick and concrete better than 2.4GHz.

The big benefit to going with Z-Wave is you’re joining 100+ other companies that provide cross-compatible support.

The big downside is you are stuck with a very proprietary protocol - even though some parts have been open sourced, you’re still marrying a single company - compare that to the dozen suppliers of ZigBee chips and multiple ZigBee stacks available.

Like ZigBee, you need to have a Z-Wave gateway device to get to the Internet and enable BTLE/WiFi access

Mesh Networking

ZigBee and Z-Wave do have one thing that they do well that Ethernet/WiFi/Cellular/BTLE do not - that's 'mesh' networking. Mesh, when done right, lets you increase network range with every new device added because each radio acts as a transceiver/router. But, that's when its done well. And it's not easy to do well. In particular, mesh doesn't work nicely with low power networks because every device has to be ready to wake up at any moment and start to do a bunch of packet routing.

That said, BTLE 5.0 will have mesh capabilies, so you may want to compare BTLE 5.0 and ZigBee when designing your low power radio device. In general, BLE is still being improved and developed and is gaining more Z-Wave/ZigBee-like capabilities than the other way around.

Reasons To Use ZigBee or Z-Wave

  • Very low cost and complexity (compared to WiFi, cellular)
  • Low power
  • 802.15.4 stacks are popular and available from multiple vendors, many even bundle a microcontroller with it
  • ZigBee profiles may make your design easy - e.g. ZLL for light control or HA for home automation
  • Interoperability: May be able to join existing home area network if on a compatible profile
  • Can be mesh-networked (just watch out for power usage)

Watch out for...

  • Need a gateway for internet access
  • Need to manage your own network
  • Z-Wave chips are only available from one supplier.
  • May have to join an ‘alliance’ or pay into a proprietary network
  • DIY authentication, some security built in

Adding ZigBee to your Project

There are vast numbers of available 900 Mhz & 2.4GHz ZigBee modules and chipsets. If you want plug+play, the XBee series use a simple AT command set that you can drive from a secondary micocontroller.

 

There are also dozens of chips and modules that have a microcontroller core + ZigBee radio. You can get these chips from TI, Microchip, Atmel, NXP, SiLabs...pretty much everyone. So if you have a favorite core that you use a lot already, it's pretty easy to find one in the family with ZigBee built in!

Check out the huge offerings at DigiKey

If you want to use ZigBee Light Link, there are some nice existing dev kits such as the ATSAMR21ZLL-EK from Atmel available from DigiKey

Adding Z-Wave

For Z-Wave, there aren't as many options - remember that there's only one chip available - but you can get various modules and dev-kits built on the ZM chips.

You can see the full range of Sigma Z-Wave offerings at DigiKey

Last updated on 2017-11-01 at 04.24.04 PM Published on 2017-11-01 at 04.23.54 PM