Basics of ZigBee™
1. What is ZigBee?
2. How ZigBee came into existence?
3. Where ZigBee can be used?
4. What can ZigBee network contain?
5. What are the features of ZigBee?
6. What are the layers in ZigBee?
7. What are the device types in the ZigBee network?
8. What are the frame structures supported by ZigBee?
9. What are advantage of cluster / mesh network over star networks?
10. What is CSMA – CA Technology?
11. What is CSMA – CD Technology?
Basics of Microchip ZigBee
1. What does Microchip offer for ZigBee?
2. Is the Microchip ZigBee Stack fully ZigBee Protocol Compliant?
3. Does the stack support both 8 and 16 bit Microchip architectures?
4. What application profiles does the Microchip stack support?
5. What are memory requirements of the Microchip ZigBee stack?
6. What are the frame structures supported by Microchip ZigBee Stack?
7. Which are the transceivers supported by the Microchip ZigBee Stack?
8. How will the parent node respond to the child node if it goes out of the vicinity
and then again comes back, in a ZigBee network?
9. Can an RFD node have more than one Coordinator in a ZigBee network?
10. How do I change the MAC address if I am using multiple RFDs in my ZigBee
Network?
11. Can Heap allocated space on the RAM (data memory) be transferred on to
the Flash in ZigBee Stack?
12. What is the effect of reducing heap size for the over all performance ZigBee
stack?
13. Does heap size reduction require re-certification of ZigBee Stack?
14. As ZigBee network supports 65536 devices. With the current stack will it
support all 65536 devices?
15. With the addition of each extra RFD, what is the memory (RAM and Flash /
EEPROM) requirement on the PAN Coordinator and Coordinator side?
16. What is the most important thing the customers can take advantage of from
Microchip ZigBee Stack?
17. What are the basic requirements for a PIC MCU in a ZigBee application?
Basics of ZigBee
1. What is ZigBee?
ZigBee is a standard for embedded application software and has been ratified in
late 2004 under IEEE 802.15.4 Wireless Networking Standards.
ZigBee is an established set of specifications for wireless personal area
networking (WPAN), i.e., lighting control among related devices. This kind of
network eliminates use of physical data buses like USB and Ethernet cables. The
devices could include telephones, hand-held digital assistants, sensors and
controls located within a few meters of each other.
ZigBee is one of the global standards of communication protocol formulated by
the relevant task force under the IEEE 802.15 working group
2. How ZigBee came into existence?
The ZigBee Alliance has been set up as “an association of companies working
together to enable reliable, cost-effective, low-power, wirelessly networked,
monitoring and control products based on an open global standard”. For the first
time, companies will have a standards-based wireless platform optimized for the
unique needs of remote monitoring and control applications, including simplicity,
reliability, low-cost and low-power”.
3. Where ZigBee can be used?
The goal is “to provide the consumer with ultimate flexibility, mobility, and ease of
use by building wireless intelligence and capabilities into every day devices.
ZigBee technology will be embedded in a wide range of products and
applications across consumer, commercial, industrial and government markets
worldwide. Presently this includes broadly the Home Automation, Building
Automation, Consumer Electronics, Personal Health Care and Industrial
Automation categories.
Some of the direct applications are:
Security
HVAC
Lighting Control
Access Control
PC & Peripherals
Remote controls for TV/DVD
4. What can ZigBee network contain?
The target networks encompass a wide range of devices with low data rates in
the Industrial, Scientific and Medical (ISM) radio bands, with building-automation
controls like intruder/fire alarms, thermostats and remote (wireless) switches,
video/audio remote controls likely to be the most popular applications. So far
sensor and control devices have been marketed as proprietary items for want of
a standard. With acceptance and implementation of ZigBee, interoperability will
be enabled in multi-purpose, self-organizing mesh networks.
5. What are the features of ZigBee?
1. Has low power consumption with battery life ranging from months to years.
(Operates in discontinuous Tx/Rx mode or sleep mode)
2. Maximum data rates allowed for each of these frequency bands are fixed as
250 kbps @2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz.
3. High throughput and low latency for low duty-cycle applications (<0.1%)
4. Channel access using Carrier Sense Multiple Access with Collision Avoidance
(CSMA-CA)
5. Addressing space of up to 64-bit IEEE address devices, 65,535 nodes per
network and support typical range of 50 M.
6. Fully reliable “hand-shake” data transfer protocol.
7. Supports network topologies like star, peer-to-peer, mesh and cluster tree
6. What are the layers in ZigBee?
The ZigBee Standard has evolved standardized sets of solutions, called ‘layers'.
These layers facilitate the features that make ZigBee very attractive: low cost,
easy implementation, reliable data transfer, short-range operations, very low
power consumption and adequate security features. The layers are
Application Support layer
Network Layer
Media access control (MAC) layer
Physical (PHY) layer
For more details please refer the application note AN965 (Microchip Stack for the
ZigBee Protocol) from the link
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
7. What are the device types in the ZigBee network?
There are three different ZigBee device types that operate in any self-organizing
application network.
Coordinator
Router
End Device( either full function FFD or reduced function RFD devices)
For more details please refer the application note AN965 (Microchip Stack for the
ZigBee Protocol) from the link
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
8. What are the frame structures supported by ZigBee?
The four frame structures are :
Beacon frame for transmission of beacons
Data frame for all data transfers
Acknowledgement frame for successful frame receipt confirmations
MAC command frame
9. What are advantage of cluster / mesh network over star networks?
The cluster and mesh network are also known as a multi-hop network, due to
their abilities to route packets between multiple networks, while the star network
is called a single-hop network. The mesh network allows the designer the
extended the physical range of the network, and to provide adequate
redundancy.
10. What is CSMA – CA Technology?
CSMA – CA is Carrier sense multiple access collision avoidance, CSMA/CA is a
modification of pure CSMA. Collision avoidance is used to improve the
performance of CSMA by attempting to be less "greedy" on the channel. If the
channel is sensed busy before transmission then the transmission is deferred for
a "random" backl-off interval. This reduces the probability of collisions on the
channel.
11. What is CSMA – CD Technology?
CSMA – CD is Carrier sense multiple access collision detection, is a network
control protocol in which
a carrier sensing scheme is used.
a transmitting data station that detects another signal while transmitting a frame,
stops transmitting that frame, transmits a jam signal, and then waits for a random
time interval (known as "backoff delay" and determined using the truncated
binary exponential backoff algorithm) before trying to send that frame again.
Collision detection is used to improve CSMA performance by terminating
transmission as soon as a collision is detected, and reducing the probability of a
second collision on retry, also methods for collision detection are media
dependent.
Basics of Microchip ZigBee
1. What does Microchip offer for ZigBee?
Microchip offers the following to support ZigBee :
Zero-cost-license and royalty-free ZigBee protocol stack
Source-code format, allowing designers to customize their products
ZigBee compliant transceiver called MRF24J40 (MRF24J40 is a 2.4 GHz IEEE
802.15.4 transceiver targeted for the ZigBee protocol)
ZigBee compliant transceiver module called MRF24J40MA (MRF24J40MA is an
agency certified transceiver module based on the MRF24J40)
Hardware support tools include
PICDEM Z MRF24J40 2.4 GHz Daughter Card
PICDEM Z 2.4 GHz DEMO KIT
ZENA (ZigBee) NETWORK ANALYZER
2. Is the Microchip ZigBee Stack fully ZigBee Protocol Compliant?
Version 1.0-3.8 of the Microchip Stack for the ZigBee Protocol provides all the
required features of the v1.0 ZigBee protocol specification (except those
limitations listed below) with a simple interface in a minimum amount of program
memory. This version has passed ZigBee Compliant Platform (ZCP) certification
1.0 from ZigBee Alliance and is certified to be able to work with other certified
ZigBee devices.
Note - Limitations from the ZigBee Protocol and IEEE 802.15.4 Specifications
1. Only security residential mode is supported.
2. Only non-beacon networks are supported. This is an IEEE 802.15.4 limitation
only.
Currently, ZigBee specifies only non-beacon networks.
For more details and update on please refer the Microchip ZigBee Stack from the
link
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
3. Does the stack support both 8 and 16 bit Microchip architectures?
Microchip has developed two different stacks supporting 8 and 16 bit Microchip
architectures
8 bit - PIC18F/PIC18FxxJ architectures - AN965 Stack v1.0-3.8 for PIC18
16 bit - PIC24H/PIC33F architectures - AN965 Stack v1.0-3.8.1 for PIC24 and
dsPIC33 . However the 16-bit stack is not ZigBee certified.
For more details please refer the link
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
4. What application profiles does the Microchip stack support?
Currently Microchip supports the Home Control Lighting Profile along with the
ZigBee stack.
5. What are memory requirements of the Microchip ZigBee stack?
Approximate program memory requirements for the Microchip ZigBee stack (Ver
3.80) are as follows. These numbers include
Minimum binding and neighbor table size as specified by the Stack Profile.
All optimizations enabled. Procedural-abstraction passes to set to 4.
All start-up code, initialization, interrupt vectors, and required libraries are
included.
Following stack size is for PIC18LF4620 microcontroller. Stack size for other
PIC18 family (8-bit) microcontrollers may have small differences.
Without Security (KB)
With Security (KB)
Coordinator
39.7
46.1
Router
32.9
39.3
End Device (RFD)
20.9
26.4
Following stack size is for dsPIC33FJ256GP710 microcontroller. Stack size for
other 16-bit microcontrollers may have small differences.
Without Security (KB)
With Security (KB)
Coordinator
38.9
44.0
Router
32.1
36.9
End Device (RFD)
22.3
26.2
RAM requirements are highly dependent on the application configuration. A
simple RFD will require at least 5 banks of available RAM. Coordinators and
Routers can require a great deal more, especially if they have RFD children.
Refer to the latest AN965 for more information.
For more details and update on please refer the Microchip ZigBee Stack from the
link,
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
6. What are the frame structures supported by Microchip ZigBee Stack?
Microchip stack supports all the four ZigBee frames.
7. Which are the transceivers supported by the Microchip ZigBee Stack?
Version 1.0-3.8 of the Microchip Stack for the ZigBee Protocol supports
Microchip MRF24J40 and UBEC UZ2400.
For more details on device update on please refer the Microchip ZigBee Stack
readme file from the link
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1
824&appnote=en021878
8. How will the parent node respond to the child node if it goes out of the vicinity
and then again comes back, in a ZigBee network?
Once the child note gets out of the vicinity / switches off from of the parent node,
the parent node will not have any information of the child node. However it is the
duty of the child node to scan through again once it switches on / gets into the
vicinity of the same parent node or a different parent node.
9. Can an RFD node have more than one Coordinator in a ZigBee network?
The RFD nodes can communicate or register itself with only one coordinator at a
time, which becomes its parent node. If the RFD leaves the its current parent, it
can register itself with another parent node.
10. How do I change the MAC address if I am using multiple RFDs in my ZigBee
Netwrok?
There are two ways of changing the MAC address,
From the program, each RFD is compiled with a ZigBee.def file. The file contains
the following below MAC address which is 64-bit and later converted to a short
address of 16-bit.
RFD 1 // Device MAC Address
#define MAC_LONG_ADDR_BYTE7 0x00
#define MAC_LONG_ADDR_BYTE6 0x04
#define MAC_LONG_ADDR_BYTE5 0xA3
#define MAC_LONG_ADDR_BYTE4 0x00
#define MAC_LONG_ADDR_BYTE3 0x00
#define MAC_LONG_ADDR_BYTE2 0x00
#define MAC_LONG_ADDR_BYTE1 0x00
#define MAC_LONG_ADDR_BYTE0 0x67
Similarly we need to change for RDF 2 also
RFD2 // Device MAC Address
#define MAC_LONG_ADDR_BYTE7 0x00
#define MAC_LONG_ADDR_BYTE6 0x04
#define MAC_LONG_ADDR_BYTE5 0xA3
#define MAC_LONG_ADDR_BYTE4 0x0
#define MAC_LONG_ADDR_BYTE3 0x0
#define MAC_LONG_ADDR_BYTE2 0x0
#define MAC_LONG_ADDR_BYTE1 0x0
#define MAC_LONG_ADDR_BYTE0 0x68
etc. for different RFD files.
Through the ZENA Analyzer, if you are using ZENA Analyzer then you can
change the MAC address as follows:
1. Open ZENA Analyzer (Software on PC)
2. Specify you required MAC address as
#define MAC_LONG_ADDR_BYTE7 0x00 Common for all RFDs (as from
Vendor ID)
#define MAC_LONG_ADDR_BYTE6 0x04 Common for all RFDs (as from
Vendor ID)
#define MAC_LONG_ADDR_BYTE5 0xA3 Common for all RFDs (as from
Vendor ID)
#define MAC_LONG_ADDR_BYTE4 0x00
#define MAC_LONG_ADDR_BYTE3 0x00
#define MAC_LONG_ADDR_BYTE2 0x00
#define MAC_LONG_ADDR_BYTE1 0x00
#define MAC_LONG_ADDR_BYTE0 0x68 Byte address changed as required
3. Specify no. of End Points
4. Generate Files
That software will create the MyZigBee.c, ZigBee.def, Zlink.lkr files for you.
11. Can Heap allocated space on the RAM (data memory) be transferred on to
the Flash in ZigBee Stack?
The PIC18 has 64-byte sectors for the Flash, which needs to copied, changed
and then re-written each time there is an update of data. The Heap and stack
are the most dynamic portions of memory and moving them to flash is not
practical, you would automatically incur a 2-ms sector write overhead for EVERY
FUNCTION CALL. This might reduce the throughput of the system drastically
and hence not recommended at all. The Stack and Heap ought to reside in RAM.
12. What is the effect of reducing heap size for the over all performance ZigBee
stack?
Heap size is reserved for dynamic memory allocation in the stack. Reduced heap
size may reduce the performance and may reject packets in the heavily loaded
system especially for Coordinator. 1K heap would be enough for some small
demo i.e. LIGHT – SWITCH demo, it depends on the application and how much
data to send.
13. Does heap size reduction require re-certification of ZigBee Stack?
Changing heap size will not require recertification.
14. As ZigBee network supports 65536 devices. With the current stack will it
support all 65536 devices?
Yes. The data that supports devices being added to the network are not stored
on the stack, so there is not a direct relationship between the number of the
devices on the network and the stack size. But as a practical matter, the PIC18
will not support 64K devices, because with that many devices on the network, the
routing table, neighbor table etc, would not fit on the 64K PIC part.
15. With the addition of each extra RFD, what is the memory (RAM and Flash /
EEPROM) requirement on the PAN Coordinator and Coordinator side?
When the network is formed by a Coordinator, the MCHP ZigBee stack is
configured to specify the maximum number of End Devices, Routers and max
depth of the network. These parameters are used to set the upper limited how
many devices can be supported. Hence this is purely dependent on the network
topology.
Say for example if you consider Mesh routing. Based on the structures like in
currentNeighborTableInfo and neighborTableInfo in the coordinator any
additional neighboring device added in the network will increase the memory size
by around 25-32 bytes.
16. What is the most important thing the customers can take advantage of from
Microchip ZigBee Stack?
The most important thing is that the Stack is certified. With certification comes
the stamp of approval that the mandatory features are all in place. Also MCHP
ZigBee stack is one of the smallest code-size wise because we give the
customer the option of customizing it for their specific application and device type
(Coordinator, Router and End Devices are built separately – not a single library).
The size of the neighbor table, binding table etc can be customized etc. Most of
our customers are evaluating ZigBee as a part of their overall RF solution.
17. What are the basic requirements for a PIC MCU in a ZigBee application?
The Microchip ZigBee protocol stack runs on PIC18 devices. The basic
operating requirements for the PIC MCU are sufficient memory space for the
ZigBee stack and application code, SPI interface, and Enhanced Flash program
memory. The Enhanced Flash self-write capability of PIC18 MCUs is used at run
time in the ZigBee stack to configure the network and recognize and bind new
network members.
The Reduced Function Device (RFD) protocol stack requires approximately 10K
bytes Flash program memory. This size is based on our v0.9 specification
implementation. The ZigBee stack will be updated to the v1.0 specification. Any
of Microchip’s PIC18 Enhanced Flash MCUs with greater than 16K bytes Flash
program memory can support the stack. The final device decision is dependent
on the type of ZigBee node and the application code size. Microchip offers over
30 PIC18 Enhanced Microcontrollers with 28 to 80 pins and 32 K bytes to 128 K
bytes Flash program memory.
The RF transceivers are 3.3V devices so a PIC18LF, wide voltage, MCU enables
a single supply design. A PIC MCU can be used at 5V for additional
performance or features. However, a 3V supply will be required for the RF
transceiver as well as level translation for the PIC18F to RF transceiver interface.