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[Mesh]

Hi again,

What's all the "buzz" about ZigBee? (pun intended  ) I'm not familiar with wireless protocols but ZigBee in particular is popping up just about everywhere. Can anyone share their experiences with ZigBee? (i.e. anyone have a ZigBee network installed and running?) What separates the protocol from others like WiFi or Bluetooth?

Mesh

[emmsys]

Hi Mesh,

Viconics has been an active participant in the ZigBee Alliance for over a year, taking part in numerous profile task groups (PTGs) and ZigBee Member meetings. I was vice-chair of the HVAC PTG for a while as well. The ZigBee Alliance is a consortium of companies around the world, working together to define an interoperable, low power, wirelessly networked protocol for monitoring and control http://www.zigbee.org . The ZigBee protocol defines the OSI layers above the MAC and PHY layer. These include the networking and security layers as well as the application framework. ZigBee runs on the low power, low data rate 802.15.4 specification. That immediately separates it from Bluetooth and WiFi which run on 802.15.1 and 802.11 respectively. 802.15.4 is the slowest of the 3 (250kbps versus 1Mbps and 54Mbps, with lower power consumption as well and smaller stack size.  This makes ZigBee much more suitable for sensor and control applications. With regards to experiences with ZigBee, there are currently no ZigBee certified products on the market yet (to my knowledge). Wireless technology poses new hurdles that are yet to be fully realized and documented, which may be one of the reasons why ZigBee technology has not been adopted yet.

[Mesh]

Hi Ettore,

Thank you for the information! So the fact that ZigBee, WiFi and Bluetooth use different IEEE standards means they cannot communicate with each other right? They are all running at 2.4GHz though. Does that mean they can interfere with each other?  Furthermore, it seems like ZigBee and 802.15.4 are synonymous with each other. Is ZigBee the same as 802.15.4? 

Mesh

[emmsys]

Hi,

You are correct that WiFi, Bluetooth and ZigBee all run on 2.4GHz. Actually, ZigBee has an 868/915MHz PHY layer as well but so far the 2.4GHz is the most widely known. The 868MHz layer runs at 25kbps, the 915MHz layer at 40kbps and the 2.4GHz layer at 250kpbs. The 3 IEEE standards are quite different and are thus incompatible. As with anything running in the same frequency band, all 3 standards can interfere with each other if the networks are not setup properly. It's the same with 2.4GHz phones and microwaves.

ZigBee is probably the most popular of protocols running on 802.15.4 and that is why it's synonymous with the IEEE standard. ZigBee is actually defining the OSI layers above the 802.15.4 PHY and MAC layers.

[DV8]

Mesh,

How are you doing?
I've heard through the grapevine that a Developers’ Conference will be hosted by the ZigBee Alliance in San Jose, CA, at the McEnery Convention Center on April 3-5 2007 in conjunction with the Embedded Systems Conference, Silicon Valley. Since you seem to be heavy all the technology revolving around Zigbee, I was wondering if you were going to attend?

If you do let us know what goes down.

Thanks

DV8

[emmsys]

Hi DV8 and Mesh,

The ZigBee Developers conference is a great place to see different ZigBee development platforms all in one location. I have been to a number of ZigBee technology forums and training sessions so I definitely recommend attending the developers conference. There's no better way to see which platform suits your needs best. The developers conferences usually have a few different tracks, allowing you to attend more than one platform developer during your visit.

e

[Mesh]

Hi,

The developers forum sounds interesting! Hope my boss lets me go!  What should I look for when deciding on a  hardware vendor?

Mesh

[emmsys]

Hi Mesh,

Lots of good questions! Keep it up!

First off, you need to decide if you require a System-on-Chip (SoC) design or separate radio and microcontroller. SoC are generally cheaper than the 2 chip solution but you might be limited on flash size and peripherals. With 2 chips you sometimes get the luxury of picking the microcontroller that best suits your needs.

Different vendors have different transceivers. You should look out for power consumption (TX/RX), power savings (in various sleep modes), interference rejection, form factor, cost and external component requirements. Some vendors have transceivers that require very little in terms of external components, while others require a lot more. This can result in cost savings and less variation when it comes to the RF characteristics of external components.

You can't have hardware without software so always look at the ZigBee stack provided by the vendors. Check out the size, the availability of demos, the ease of use and the integrated development environments available (as well as their cost).

e

[amigo]

Okay I need a refresher of sorts:

Let's say I have a HMI touch screen which the manufacturer says has a zigbee module/transmitter/receiver,
Now I also have a zigbee thermostat from a separate/different manufacturer.

How do I display and control data from my HMI?
What documentation does a zigbee device manufacturer provides that makes integration of different zigbee devices possible?.
Is there standards for data types, structures,etc. Is there device profiles(read: device has standard set of datapoints) in zigbee.
Do you get where I am going? I understand that zigbee defines OSI layers implementation data,but how are the data structures defined?

Thanks,
Amigo

[emmsys]

Hi Amigo,

You've asked a number of excellent questions!

First, check the frequency that the ZigBee device is running at. Although 2.4GHz is by far the most popular, there are some 900MHz transceivers popping up on the market. If your thermostat and HMI are running at different frequencies then you're simply out of luck! 

Second, you need to know what type of ZigBee profile is running on the HMI and the thermostat. There are 2 types of profiles:

1) Manufacturer Specific (MS)
2) ZigBee Certified Product (ZCP)

The first type of profile is company specific. If the HMI and the thermostat are each running their own MS profile then they will not be able to communicate with each other. Each manufacturer is allocated MS Profile IDs so there will not be any confusion.

A ZCP is a product that has undergone ZigBee certification and runs a certified ZigBee profile. These profiles cover a gamut of industries (Home Automation, Commercial Building Automation, Automatic Meter Reading etc.). Two devices can communicate with each other if they support the same ZigBee profile. These profiles come about from the hard work of ZigBee members. A tremendous amount of effort goes into defining the profiles available to the public.

One small note, a ZigBee profile usually runs on a ZigBee Stack profile. There are 2 stack profiles:

1) ZigBee 2006
2) ZigBee Pro

The stack profiles support different types of addressing schemes, features etc. that are more suited to the profiles that run on them.

So to answer your questions: yes ZigBee defines standards for data types and messages. A ZigBee profile is a collection of device descriptions. For example, the Home Automation profile has device descriptions for light switches, thermostats etc. These devices are made up of ZigBee clusters, which define messages or attributes (datapoints). For example, a thermostat can have an attributes for room temperature, display setting (degrees F or C) etc. Another cluster could define the messages that command the devices (like changing the setpoints on the thermostat).

As for the documentation that a manufacturer supplies, I think the ZigBee marketing workgroup is looking at different ways (like logos, blurbs etc.) for that. I need to look into it more but you would definitely need to know the information above to make sure that 2 devices are compatible. Hope this helps!

e

[amigo]

Okay emmsys, thank you for the reply.

I understand the frequencies being the same.

Now, all the other things are very inetersting as well as complicated for simple user/buyer to check.
All zigbee or proclaimed to be zigbee products that I have seen provide no such information that I can readily find.

Are the products that you know that provide this sort of documentation, readily, online?

I mean to get two zigbee devices from the same manufacturer to talk to each other is nice, but does not really interest a person like me or any other real integrator that wants to mix and match different product lines.

[Zinc22]

May I pitch in my 2 cents on the commercial control side 

Zigbee as it stands today........

A Zigbee device will use a what is typically called a Zigbee radio chip. ( 900 or 2.4 )

However, the Zigbee device may use one of the following:
- A proprietary mesh stack
- The open Zigbee mesh stack

Again, all on the same processor chip component.

As it stands today on the Zigbee side, a lot of the necessity for open interoperability is currently in the brewing and being defined:
- Application profiles
- Point definition
- Network and database tools
- Etc....

Viconics is a very active member for the Zigbee open HVAC temperature control standards.

In therms of interop, Zigbee is where LON was about 10 years ago and BACnet 5 years ago.

So to your question. Even if the device uses the open Zigbee mesh stack, most manufacturer only use the physical layer of the protocol. I.E. They will use proprietary messages between each devices because the standards are not advance yet enough to get to the same plug and play interop found in wired open standard networks.

However, the technology is now robust enough that a lot of manufacturer will release products using a set of proprietary network rules using a Zigbee chip with either a proprietary network stack or the open Zigbee stack.

To make a long story short......

The chance of having 2 devices from different manufacturer talk together today is pretty slim  :

However, if you look at Zigbee.org, you will see the amount of work behind poured behind the standards by a sizable number of manufacturer. Interop will the the goodies will happen pretty soon I think so.

So why do manufacturer release products with a Zigbee tag even if they are proprietary ?

- The technology is robust enough for the market and it's cost is now where it will be more cost effective than pulling wires in certain area where labour is expensive.

- Also, there will be gateways translating the information from wireless to today's open wired standards ( BACnet & LON ). Making the most use of what is available with today's commercial control system.

There will be ( and is today ) a lot of wireless residential system available and they will offer all the peripheral component needed under one brand and one stop. However, for commercial applications.....we are not there yet. 

Stay tuned for more interesting things from Viconics pretty, pretty soon.

[amigo]

Thanks Zinc.

Can you possibly please point me to a BACnet or LON zigbee translating gateway?
I am curious if such devices exist presently, if so how many.

[Zinc22]

Here you go.

I sent you a PM with a PDF attachement.

Planned for release soon.