Grad Project : Design Issues in Wireless Sensor Networks using CC2530 Zigbee Network Processor under Dr. Asis Nasipuri [anasipur@uncc.edu]

1. Design Issues in Wireless Sensor Networks using CC2530 Zigbee Network Processor
Sreekesh Padmanabhan
Electrical Engineering Department
University Of North Carolina at Charlotte - NC, USA
sreekeshpadmanabhan@gmail.com
Abstract—Deployment of medium to large size wireless sensor
networks with optimum power consumption has always been a
topic of high research interest. This project investigates the
design issues for the development of wireless sensor networks
with CC2530 ZNP devices, with a network Coordinator, end
devices, and routers as network nodes. With the onboard sensors
and multiple low power modes, the CC2530 ZNP can be
configured for maximum efficiency, shutting off the processor
clocks and peripherals and waking up as per the energy
efficiency requirements. In this project, a multi hop wireless
network is deployed using Z-stack and experiments are
performed to evaluate the power consumption in the end device
and comparison of the low power modes performed.
Index Terms—CC2530 ZNP, Zigbee, Low power.
I. INTRODUCTION
Wireless sensor networks (WSN) have been used in various
home automation systems, industrial and medical applications
and embedded smart energy utilities. AWSN typically consists
of multiple end devices that are deployed over a geographical
location to collect various data through external or inbuilt
sensors, and relayed over the network routers to the network
gateway coordinator, which then process the data for analysis.
The research and development works for such networks were
originally initiated for military applications but gradually
became a part of the consumer and industrial application.
Multiple wireless sensor devices from different vendors are
available in the market: includes Crossbow’s Mica family of
Motes, Ember Corporation’s Zigbee EM35x SoC, Smart Dusts
aimed at developing sensor nodes of micro, to name a few.
Texas Instrument’s CC2530 Zigbee based solutions are one of
the prominent devices in the market. Available in different
designs and features, CC2530 Zigbee network Processor Mini
kits are one of the modules that are highly portable, light
weight and easy to deploy devices, equipped with on board
sensors consuming very low power. Once programmed, the
devices can be deployed anywhere without requiring any
additional equipment, except for a computer to interface with
the coordinator.
The objective of the project is to deploy a small scale wireless
sensor network, using a CC2530 ZNP based end device, a
router and a coordinator node and study its power
consumption in various low power modes. The End device
would measure certain analog parameter values like light
intensity and temperature using the Analog and digital
converter, using SPI communication to pass the measured
values to the CC2530 transmitter, which would transmit the
packets to the coordinator device hooked to a computer using
the USB stick. In the event that the distance between the end
device and coordinator becomes large enough that the signals
do not reach the intended destination, an intermediate router
node can be deployed, which would receive the packets
transmitted by the end device and route them to the
coordinator. Additional routers can be placed to further extend
the range of transmission. The received data is displayed by
the coordinator on to the hyper terminal.
This report is organized as follows. Section 2 touches upon
the related works in this domain. Section 3 of the document
provides the Hardware description details, describing the
CC2530 ZNP Mini system components and the CC2430 ZNP
Mini devices. It also introduces the Zigbee network protocol
and its variant, the Zstack and how the system components are
placed over the Network stack. Section 4 briefs the Integrated
Development Software Platforms involved: IAR & Code
Composer studio. Section 5 involves the MSP Embedded
architecture and components: Watch Dog Timer, Timers,
Clocks, General Input/Output Pins, Serial Communication,
Analog to Digital Converters and the low power modes.
Section 6 provides insight into the Network Configurations and
protocols, including the Network parameters, Zigbee network
creation, joining a Zigbee network and Routing protocol
involved. Section 7 encapsulates the current consumption
analysis in CC2530 ZNP Mini devices in its subsections. The
measurement setup is graphically described along with the
current calculation fundamentals. Besides these, the design
considerations for low power operations are dealt. The project
involved transmission and polling experimental analysis of end
devices, recording the oscilloscope plots, tabulating the
measured values and calculating the current consumption.
Behavioral analysis of events in end device and router were
conducted. Eventually, a comparative study of low power
modes was done.
II. RELATED WORK
Wireless sensor networks in low power modes is a highly
researched topic, with good research publications available.
Article [1] describes the utilization of minimum energy in
various scenarios, related technologies involved like signaling,
networking and the software optimizations. It gives an
overview of the node architectures, voltage scaling and the
hardware involved. The parameters of energy efficient
networks like the signal processing, computational algorithms
in parallel processing and energy efficiency of layers are
briefed. Finally, the operating systems and software are
considered.
1

2. Article [2] proposes the enhanced hierarchical routing
protocol (ERHP) for Zigbee mesh networks, which aims at
finding the shortest path for communication between Zigbee
based devices, reducing overheads and delays. The article
mentions about Zigbee networks combining hierarchical
addressing scheme protocols with ad-hoc on demand distance
vector protocol. Enhanced hierarchical routing protocol uses
the short cut to destination using the link to neighbor nodes
based on Zigbee hierarchical addressing scheme along with the
next hop relay node having the shortest hierarchical path to
destination. The proposal also mentions about routing path
recovery in case of link failure.
hence each of the boards can be programmed to be either
coordinator, router, or end-device.
Zigbee is a communication protocol specification, using low
power radios based on IEEE 802.15.4 standards, used to
transmit data over long distance through intermediate routers
in mesh networks. Zigbee standards have frequency of
operation in 2.4GHz or 915 Mhz or 868Mhz range.
III. CC2530 ZIGBEE NETWORK PROCESSOR MINI
Zstack is Texas Instruments Zigbee compliant protocol stack
for IEEE 802.15.4 products and platforms. Z-Stack is
compliant with the ZigBee 2007 (ZigBee and ZigBee PRO)
specification, supporting ZigBee 2007 on CC2530 SoC,
MSP430+CC2520 and Stellaris LM3S9B96+CC2520.[4].
The CC2530 ZNP Mini Development Kit is designed for
ZigBee Networks, providing ZigBee interface to any
application using a simple serial interface. The ZNP mini kit
has three target boards, two of which can be mobile using two
AAA batteries - used as end devices and routers. The target
board sensor includes sensors that can be combined with led
lights and push buttons for various applications. Figure 1
depicts the ZNP Mini kit.
The application processor can be connected to the CC2530
SoC based ZNP to obtain ZigBee connectivity. The
Application Processor describes the Processor/MCU that is
running the application code, which uses CC2530-ZNP API
over the UART/SPI/USB interface to communicate with the
ZNP providing ZigBee connectivity with its IEEE 802.15.4
radio. Figure 2 illustrate the Application over Zigbee stack.
Fig. 1. End device, Router and Coordinator [3]
The Zigbee Network Processor development kit is simple
enough yet designed to give an introduction to ZigBee
wireless networks. The hardware consists of:
• MSP430F2274 microcontroller controlling ZigBee device.
• CC2530 ZigBee device preloaded with ZigBee firmware.
Fig. 2. Application over Zigbee Stack [5]
IV. SOFTWARE PLATFORM
The device types in the network includes the following:
• ZigBee coordinator (ZC): The coordinator is the root of
any Zigbee network tree. Only one ZigBee coordinator
exists in each network. It stores all network information.
• ZigBee End Device (ZED): End devices are loaded with
functionality to talk to coordinator or a router parent node.
• ZigBee Router (ZR): A Router can run application
function, as well as can act as an intermediate router,
relaying data from other devices.
IAR Embedded Workbench is a high-performance
C/C++ compiler and debugger tool suite for applications based
on 8-, 16-, and 32-bit microcontrollers, including MSP430s.
Most of open source code for MSP430 is coded in IAR, but it
has a limitation that the free version allows only a code limit of
4kB, which is enough for small scale developments but will not
suffice for any application developments like Multi Hop
networks. Thus, Code Composer was used to develop Multi
Hop network application.
The one and only coordinator in the Zigbee network is
responsible to set up the network, configuring the ZigBee
network parameters. The end-devices periodically poll their
key data to coordinator. The target boards can also be
programmed as routers through software. Routers typically
route messages from other devices, thus extending ZigBee
networks. All the target boards has identical hardware and
Code Composer Studio (CCStudio) is an integrated
development environment (IDE) for Texas Instruments (TI)
embedded processor families to develop and debug embedded
applications. Since the available examples for CC2530 ZNP
Mini was all compiled for IAR Embedded Workbench, all the
code had to be translated to Code Composer. It involved code
analysis and rectifying errors while maintain the code logic,
and in the process understanding Z-stack protocol stack.
2

3. V. MSP EMBEDDED SYSTEM COMPONENTS
A. MSP Architecture
The MSP430 is powered by a 16-bit RISC CPU, multiple
clocks and peripherals, interconnected using a von-Neumann
common memory address bus (MAB) and memory data bus
(MDB). The key features of the architecture include:
•Architecture based on Ultralow-power modes.
•High-performance analog ideal for precision measurement
•16-bit RISC CPU supporting applications of low code size.
•In-system programmable Flash permits flexible code
changes, field upgrades and data logging
restarts counting from zero. CCIFG and TAIFG interrupt flags
are set by the timer events:
CCIFG interrupt flag is set when timer counts to the TACCR0
value. TAIFG interrupt flag is set when the timer counts from
TACCR0 to zero. The timer in UP mode is illustrated in
Figure 4.
0FFFh
TACCR0
Fig. 4. Timer A in UP mode.
D. Clock Modules
The MSP architecture includes three clock sources:
• LFXT1CLK: Low-frequency/high-frequency oscillator.
• DCOCLK: Digitally controlled oscillator (DCO).
• VLOCLK: Internal very low power, low frequency oscillator
with 12-kHz typical frequency.
Fig. 3. MSP Architecture [6].
B. Watch Dog Timer
Programming MSPs usually involves first configuring the
system Watch Dog Timer, which is a 16-bit timer that can be
used as a watchdog or as an interval timer. The primary
function of the WDT+ module is to perform a controlled
system restart after a software problem occurs. If the selected
time interval expires, a system reset is generated. The code line
WDTCTL = WDTPW+WDTHOLD; will stop the Watchdog
timer.
The clocks sources three clock signals:
• ACLK: Auxiliary clock, sourced from LFXT1CLK or
VLOCLK, and signals individual peripheral.
• MCLK: Master clock, is powered by LFXT1CLK,
VLOCLK, XT2CLK and are used by the CPU.
• SMCLK: Sub-main clock is sourced from LFXT1CLK,
VLOCLK or DCOCLK, used by peripherals.
E. General Pin Input Output
The MSP430 used have 4 different ports, each with 8 pins
and 8 bit registers that control them and provide information
about their current status. Table II briefs the port register bit
status.
TABLE II. GENERAL PIN INPUT OUTPUT REGISTERS
Register
Bit value at 0
Bit value at 1
PxIN
TABLE I. TIMER OPERATION MODES
Mode
Operation
Stop
Timer stops
Up
Repeatedly counts from zero to TACCR0 & back to zero
The output is low
The output is high
port pin is switched to
input direction
Pullup/pulldown resistor
disabled
port pin is switched to output
direction
Pullup/pulldown resistor
enabled
Resistor in PULL-DOWN
Resistor in PULL-UP
PXIES
PxIFGx flag set low-tohigh transition
PxIFGx flag set high-to-low
transition
PXIE
interrupt is disabled
Interrupt is enabled
PXIFG
No interrupt is pending
Interrupt is pending
PxDIR
PxREN
Repeats count from zero to TACCR0
Up/Down
PxOUT
Repeats count from zero to TACCR0
Continuous
The input is high
PxOUT
C. Timers
The MSP430 has 2 timers: Timer A and Timer B. Timer_A
is a 16-bit timer/counter with multiple capture/compare
registers. The timer has four modes of operation as given in
Table I.
The input is low
In the UP mode, the timer repeatedly counts up to the value of
compare register TACCR0, which defines the period. Once
the timer value reaches TACCR0, the timer is reset and
F. Analog to Digital Converter
The MSP430 is equipped with a 10-bit analog-to-digital
converter ADC10 module. The module includes a 10-bit SAR
core, data transfer controller (DTC), sample select control and
a reference generator. The DTC allows ADC10 samples to be
converted and stored anywhere in memory without CPU
3

4. intervention. Two registers control the ADC10: ADC10CTL0
and ADC10CTL1and enabled with the ADC10ON bit. The
ADC10 registers are altered only when ENC = 0 and hence
ENC must be set to 1 before any conversion can take place.
ADC10CLK sources include SMCLK, MCLK, ACLK, and 5MHz internal oscillator ADC10OSC.
G. Operating power modes
The MSP430 family is designed for ultralow-power
applications and uses different operating. Figure 5 illustrates
the low power modes and its corresponding current
consumption.
• Network Depth
The number of nodes from the coordinator to the device
defines the depth of a device in a network. Maximum
number of hops from the coordinator to the most distant
device in the network defines the maximum network depth,
which determines the overall diameter for the network.
• Number of Children
The Co-ordinator fixes the maximum number of child
devices per Router. Each Router in the network can have a
fixed number of child devices attached to it. These may be
either Routers or End Devices.
• Number of Child Routers
In addition to the number of children per Router, a limit is
put on how many of these children may be Routers
themselves.
A. ZigBee Network Creation
The coordinator initializes and maintains ZigBee network.
Network initialization involves the following:
Fig. 5. MSP in low power modes
[6]
The MSP is configured in various low power modes by
setting the System Clock Generator 1, System Clock Generator
2, Oscillator Bit and CPU Clock bit in the status register (SR).
Since the status register is stored into the stack before entering
an interrupt service routine, on return from interrupt service
routine, the operational mode before entering the ISR is
resumed – if the relevant bits in SR are not changed within the
ISR. On the contrary, the status bits can be altered within the
ISR, which causes the operation mode to change once the ISR
is serviced. Table III indicates the status of status register clock
bits in various low power modes, switching off CPU clocks or
other oscillators as per the mode chosen
TABLE III. LOW POWER MODES STATUS REGISTER BITS
Mode
CPU and clock status
Active
CPU & all enabled clocks active
LPM0
CPUOFF is set, thus shutting down processor
LPM1
LPM2
LPM3
LPM4
SCG0 & CPUOFF are set, thus shutting down processor &
system clock generator 0
SCG1 & CPUOFF are set, thus shutting down processor &
system clock generator 1
SCG1,SCG0,CPUOFF are set, thus shutting down processor
& & system clock generators
SCG1,SCG0,OSCOFF,CPUOFF are set, thus shutting down
processor down processor & & system clock generators
VI. NETWORK CONFIGURATION
The coordinator initializes the network to configure its
parameters and determines its shape and topology.
1. Radio Channel Setup: Radio channel on which the
communication should take place is searched, with priority to
the channel with least activity. The default radio channel is
channel 11 operating at 2405 Ghz and can range upto channel
26at 2480 Ghz.
2. PAN ID Assignment: The network is assigned a Personal
Area Network identifier or PAN ID by the coordinator. The
PAN ID should be unique and thus should not conflict with
any other PAN IDs. At this stage, the coordinator also assigns
a network (short) address to itself, with default address of
0x0000.
3. Network Startup: Once the Co-ordinator has been
configured, it responds to queries from other devices that wish
to join the network.
B. Joining a ZigBee Network
Following the network creation, the routers and end devices
can join the network. Both Routers and the coordinator allows
other end devices and routers to join the network. The join
process is as follows:
1. Network search: A network search is initiated by the node
that intends to join a network by searching the available
channels. There may be numerous networks operating in the
same channel and thus, these networks are distinguished by
the PAN IDs.
2. Parent selection: The node opts to join a router or a
coordinator with best signal amongst the numerous nodes
available within the network.
3. Join Request: The new node must get the permission from
the node it intends to join with and hence ends a message to
the Router or coordinator requesting network join permission.
4. Accept or Reject: The join request reaches the router or
coordinator with which the node intends to link and the router
or coordinator will decide about whether the node has to be
permitted or rejected. If the permission is granted, the node
can be a part of the network and will be allocated an address.
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5. C. Routing
Zigbee networks use Ad hoc On-Demand Distance
Vector (AODV) Routing protocol. This routing protocol
establishes a route to destination on demand. In AODV, the
network is silent until when a connection is required. When
demanded, the node initiates a route discovery to another node
and broadcasts a request for connection. Routing tables of
neighbor nodes are organized for establishment of routes.
AODV establishes route table entries at router nodes
dynamically, with nodes maintaining sequence numbers for
routes. Nodes forward message and keeps a track of the node
that they heard from, thus maintaining a track of the route.
Once the connectivity is done, the destination node sends a
message back to the requesting node through the temporary
route. The route that has the least number of hops through the
routers is opted for communication. [7]
VII. POWER CONSUMPTION ANALYSIS
This section presents the experiments conducted to measure
the current consumption in end devices along with the analysis
of the observations. Out of the two end pointes deployed in the
application, the sink device is mapped to the logical device
type Coordinator and the source to the logical device type: End
Device or Router. The sink receives temperature and voltage
samples sent periodically from the sources. The end device
goes to sleep to save power between the transmissions which is
how battery power consumption is optimized. All of the
measurements are done on the CC2530ZNP Mini Kit, with
only one Sink and one Source in the ZigBee network.
A. Current Measurement Setup
Current consumption measurement is done to plot the
current profile on an oscilloscope by measuring the voltage
drop across a 10 Ohm resistor. The setup is as illustrated in
figure 6.
Fig. 6. Current Measurement Setup.
To calculate the average current consumption, an end
Device and a coordinator is utilized. As indicated in the setup,
a 10 ohm resistor is connected in series with the battery, and
the oscilloscope probes measure the voltages across this
resistor. An Agilent technologies 6052A Mixed Signal
Oscilloscope (MSO) is used for this purpose to plot different
events. The oscilloscope provides a graphical representation of
the voltage drop across the resistor. Since the voltage and
current are linearly related, the oscilloscope graphical
representation indicates the current consumed by the devices.
B. Current calculation fundamentals
Since the resistor is in series with target board, the voltage at
the target board is calculated by subtracting the voltage across
the resistor from the supply voltage. Thus,
Thus, the value of the resistor R should not be too large so that
the operation of the board is not affected. The R factor will
reduce the effective voltage over the target board itself. As
long as both I and R are small enough, the voltage drop effects
are negligible. A resistor of R = 10Ω is used for the analysis.
C. Design considerations for low power operation
The ZNP Mini kit comprises of the MSP430F2274 and
CC2530. MSP430F2274 wake up time is of short duration,
with both the operating current and sleep current being low.
This low power operating modes of MSP430 makes it possible
to develop applications with just a fraction of the current other
MCU's would consume. But care must be taken to configure
MSP430 so that the current consumption is as low an average
as possible. The CC2530 ZNP Mini Kit Target Board does not
have any 32 kHz crystals connected to the MSP430, thus they
lack ultra-low power sleep timer traditional clock sources. The
only solution in many systems uses the internal high speed RC
oscillator of MCU as clock source but then, current
consumption even in “sleep” modes can be several hundred
uA, which is costly given that the system is idle. Ideally, it
should be less than 10 uA.
The MSP430F2274 utilizes a low power, low frequency
oscillator called the VLO (refer MSP Clocks previously). It can
operate in the low power mode 3, consuming only a couple of
hundred nA. The sleep timer uses VLO as the clock source.
The system thus performs periodic tasks and has a sleep current
of just a few hundred nA, even without a crystal. The halInit
function configures the MSP430 to set up the DCO to any
frequency up to 16 MHz. The current consumption though
increases with frequency of operation by logic. There should be
tradeoff between speed and current consumption. The slower
the clock, the longer time the transactions take and the longer
the MSP430 has to stay awake. However, the higher the clock
rate, the more energy you burn when the system is active.
For the application running on the eZ430-RF2530 ZNP Mini
Kit, having a high clock rate is advantageous, since there are a
lot of data being transferred over the SPI bus between the
CC2530 and the MSP430. For both the devices, it is beneficial
that these transactions (or really remote procedure calls) are
effectuated as quickly as possible, such that each device can
go to sleep mode immediately when its part of the transaction
is finished. Thus, the application has been set up to operate at
8 MHz in active mode with the on board voltage being above
2.2V. Care must be taken to ensure that all peripherals and
GPIOs on the MSP430 are configured correctly to reduce the
current consumption. Though most of the peripherals are
turned off automatically when the MSP430 enters a low power
mode, but peripherals must be turned off manually and
individually. In the application, the internal reference voltage
for the ADC had to be turned off using the following code:
ADC10CTL0 &= ~ENC;ADC10CTL0 &= ~(REFON +
5

6. ADC10ON); The General Pin Input/Output is a factor of
extensive current leakage and thus should be ensured to
configure appropriately.
D. Experimental Results
This section presents the analysis of observations obtained
from the experimental tests. Specifically, the current drawn by
the end device under different events are analyzed. The
analysis includes:
• Study of events during transmission of measured data at
interval of 4 seconds, the current consumption during an
event and calculating the average current consumption.
• Analysis of Packet transmission & request additional data
during transmission.
• Analysis of data polling at interval of 1Seconds & the
average Current Consumption
• Behavioral description of End Devices & Router
• Low power mode comparative study
The different events observed are tabulated and current
consumption during the duration of an event, noted.
Figure 8 depicts the peak events during transmission which
are depicted in dotted box in figure 7, whose frequency is set
using the timer initiation in the function initTimer(); This
schedules the CC2530 to be woken up at interval of 4 seconds
using timer interrupts, during which the end device transmits
and further goes into low power mode.
Transmission OTA
CC2530 Wake Up
LPM3
MSP430 & CC2530 in sleep
Fig. 8. Transmission Events
Table 4 records the events and the corresponding duration and
current measured during a transmission of sensor values from
end device to coordinator, as captured in Figure 8.
TABLE IV. EVENTS DURING TRANSMISSION CYCLE
1)Transmission Cycle : Figure 7 is the plot obtained for
packet transmissions at an interval of 4 seconds, with data
polling from end device to coordinator at an interval of
1Second.
Event
Description
Duration
[ms]
Current
[mA]
15.28
9.34
HAL on
174
6.0
3
CSMA-CA (RX), Tx packet, receive MAC
ACK
13.4
14.2
Sum
Polling at 1Seconds
CC2530 Wake Up
2
Transmission at 4Seconds
1
202
Average
7.5
Once the currents are analyzed, the overall average current
consumption is calculated using general formula:
1 transmission cycle
Fig. 7. Transmission and Polling cycle
The application measures the light intensity followed by
temperature values using the onboard ADCs. The measurement
duration lasts couple of milliseconds. The ADC measurements
are done while the MSP430 cores are shut off, thus reducing
power consumption to a minimum. The first peak indicates the
CC2530 waking up, starting its local oscillators, crystals and
timers. The following peak occurs when the packet is prepared
and sent over the air. At the end, the CC2530 prepares for
going back down to deep sleep to conserve battery power when
not in transmission mode. This way, power efficiency is
achieved by turning off the MCU, Transceivers and peripherals
when not in use. Events like CSMA-CA which senses the
carrier for any activity before transmission might take a short
time or a long time, depending on the traffic of the selected
channel at that instant.
= average
Where = average current consumption time,
= sleep mode Current
consumption Total time,
consumption,
= Average current consumption over period
; Knowing the above parameters,
can be calculated
based on the period of active sequences. Thus, calculate the
total life time of the system, knowing that,
LifeTime = Battery Capacity / Average Current.
For normal AAA batteries available in stores, the capacity is
typically 1200 mAh. The analysis was done using two 1.5V
AAA Duracell Alkaline Batteries.
The timer for the application is initialized to transmit the data
every 4 seconds (4000 mSec). The sleep current was measured
to be ~6uA using ampere meter. Calculating average measured
current for only transmission events in a cycle:
(202/4000)*7.5mA + (1-202/4000)*0.006mA = .384mA
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7. 2) Packet Transmission Event
The plot corresponding to packet transmission of measured
ADC values have been captured as indicated in Figure 9.
Before transmitting a packet, the end device senses the channel
to make sure that it is clear for packet transmission. Once the
channel is clear, the packets are send and the device switches to
receive mode to receive acknowledgment for the packet
transmitted. [8]
2
1
4
3 5
6
7
3) Request Additional Data
An end device will be able to receive data from another node
by periodically sending data requests to the associated device.
This packet can be send by the associated device when end
device ask for it when there are packets destined for the end
device. Figure 10 depicts the events in the peak following the
packet transmission, which requests for additional data from
the coordinator.
8
9
12
3
4
7
5
8 9
10
11
6
Fig. 10. Example of a figure caption.
Fig. 9. Transmission of Packet Over the air.
Table V records the events in the figure 8. Each event number
corresponds to the edge in figure 9.
The event values are tabulated in table VI.
TABLE VI. EVENTS DURING DATA REQUEST
TABLE V. EVENTS DURING TRANSMISSION CYCLE
Event
1
2
3
4
5
6
7
8
9
Description
MSP430 passes the data and command
over the SPI to CC2530. Once done,
MSP430 will immediately go to sleep,
and wait for acknowledgement from
CC2530 to signal that it has processed
the command
CC2530 starts the 32 MHz crystal and
sets it up as the core clock. The
command from the MSP430 is processed
and the CC2530 starts synchronizing an
internal timer in order to be able to
transmit the packet
CC2530 sets up the radio and churns the
packet through the ZigBee stack,
preparing it for transmission
Carrier sense Multiple Access Collision
avoidance is initiated by CC2530. The
radio is initially in RX mode to check
whether the channel is clear for
transmission. The duration of this step
will vary if the channel is noisy. If not
clear, the CC2530 will wait for a random
time and initiate listening again.
Once the channel is clear for
transmission, the mode is switched from
RX to TX.
In the transmission mode, the packet is
sent over the air.
The mode is switched back from TX to
RX mode to receive acknowledgements.
CC2530 receives the MAC ACK from
the associated device in the network
CC2530 enters an IDLE state, waiting to
request the APS ACK from the recipient.
Description
CC2530 is sleeping, but has only
entered LPM3, as it needs to wake up
one last time. Sensor Network
Monitor Sample Application has
configured CC2530 such that this
duration is 100 ms
CC2530 wakes up from LPM3. The
node will transmit a new data request
just to make sure that there are no
more pending data destined for the
node before it enters deep sleep. The
MSP430 is not involved in this
transaction
CC2530 starts the 32 MHz clock.
Duration
100
Current
0.008
0.5
5.5
0.5
7.6
1.45
8.0
5
Internal processing and preparing for
transmit.
CSMA-CA
1
24.7
6
Duration
0.4
Event
Switch from RX to TX.
0.2
8.5
The data request packet is sent over
the air.
Switch from TX to RX.
0.8
31.6
0.2
17.5
Receive
MAC
ACK.
This
acknowledgment does not guarantee
the successful reception of the data at
the recipient end but only indicates the
acknowledgement on MAC layer.
Post processing and prepare for deep
sleep.
Deep sleep
1
20.5
1.6
8.5
4000
0.008
Current
7
1
3.8
8.5
2
1.5
8.5
3
4
1
28.5
7
8
0.3
14
9
2
33.8
0.3
20
1.3
28.5
100
8.5
10
11
7

8. 4) Data polling
The CC2530 can be configured to automatically poll for
data (sending data requests) without involving the host MCU.
The MCU will only be notified when data is received. The
device parameter ZCD_NV_POLL_RATE manages this
polling: A CC2530-ZNP device that is configured as an enddevice will wake up periodically with this duration to check for
data with its parent device. This value is specified in
milliseconds and can range from 1 to 65000. The active
sequence of the data request is represented with the following
current profile on the oscilloscope. Figure 11 captures the
events during data polling.
coordinator realignment message but since the coordinator is
out it will not receive this. After this, the end devices will
attempt to join/rejoin a network by sending period beacon
requests. Figure 12 is the plot obtained when the end device
sends beacons to connect to a network.
Fig. 12. End Device sending beacons
Figure 13 is the plot obtained for end device once it joins a
network coordinator.
Fig. 11. Data Polling Cycle.
Table VII records the events in the above data poll cycle.
TABLE VII. EVENTS DURING TRANSMISSION CYCLE
Event
Duration
Current
1
Wake Up
Description
1.7
6.5
2
CSMA-CA (RX), transmit packet,
receive MAC ACK
4.1
22.5
3
Prepare for Sleep
1.5
6.5
Sum
7.3
Fig. 13. End Device joining a network.
Average
6) Router Behavior
14.5
In this case, the sleep current was measured to be 8 uA. The
increase in the sleep current is caused by a timer on the
CC2530 that has to be up and running to handle the timing of
the periodic data requests. For a polling period of 1
second(1000 ms), calculating the average current consumption
using :
The router searches for a network on its list of available
channels, and then joins that network as indicated in figure 14.
The average current values are indicated in the figures.
The Average current during data polling at an interval of 1Sec
is found to be:
[(7.3/1000) *14.5mA] + [(1-7.3/1000)*0.008mA] = 0.1138mA
5) End Device Behavior
Once the coordinator is disabled, end device will start
sending MAC DATA POLLs using the default configuration,
which when not responded to will, make End device think it
has lost connection with the parent and it will send an orphan
notification. For orphan notification, it expects to receive
Fig. 14. Router in search Mode
The router devices are generally not put in sleep mode,
though it is not impossible to do so – it would require
intelligent network to handle such routers. Figure 15
8

9. shows the average current once the router joins a
coordinator in the range of 25mA.
Fig. 15. Router joining network
7) Router~End Device Behavior
to low power mode as measured in the oscilloscope. This is
important, given that the idle state doesn’t engage in any
constructive activity during the sleep time, which is the
dominant fraction of the total event cycle. The low power
mode is achieved using the code:
__bis_SR_register(LPM3_bits + GIE)
This shuts down System Clock Generator 1, System Clock
Generator 2and the CPU Clock, as defined by the macro
#define LPM3_bits (SCG1+SCG0+CPUOFF)
The various low power modes of operation were studied
and the sleep currents in those modes measured. Table VIII
evaluates the average current in the corresponding low power
modes of operation. The calculations involved the transmission
peaks and the data polls at an interval of 1mSec.
TABLE VIII. SLEEP CURRENT IN LPM MODES
Fig. 17. Low power current variation region in sleep modes
Though the comparative plots are identical, there has been a
steady drop in current consumption after the packet
transmission (on zoomed analysis) when the device switched
60000
Seconds
900000
Seconds
LPM3
5.9
0.490159
0.136937
0.113389
6.4
0.49063
0.137432
0.113885
14.3
0.498073
0.145247
0.121726
LPM0
Sleep Current Variation
4000
Seconds
14.3
0.498073
0.145247
0.121726
Active
Mode
E. Low Power Mode Comparison
One of the key aspects of CC2530 ZNP lit is its low power
mode. As described previously, the ZNP goes into low power
mode 3 once the transmission is done. Figure 18 shows the
area where the current consumption value varies according to
the modes opted.
Current[uA]
LPM1
Fig. 16. End Device joining a network.
Low
Power
Mode
LPM2
The router once joined by end device relays the packets
over to the coordinator. Figure 17 displays an end device
joining a router node.
60.3
0.541415
0.190757
0.16738
The average current consumption were evaluated considering
the transmission current depicted in figure 8 and the polling
current illustrated in figure 11. The values were calculated
using excel math, varying duration and sleep current values.
Thus, without Low power mode, the sleep current consumption
is nearly 10 times more, as observed
VIII. CONCLUSION
The performance behavior of CC2430 devices was
evaluated. As seen from the results, the current consumption of
the ZNP mini devices is low in idle states and decreases when
the transmission interval increases. Thus, increasing the
interval between transmissions, especially the data polling from
end device which does not carry any measurement data, would
significantly reduce the power consumption and thus increase
the battery life. The analysis can be extended to larger
networks with multiple routers. The low power consumption
was intelligently achieved by switching of the clocks and
peripherals when not in used and turning on when required.
The overall reduction in the current consumption with and
without low power modes were compared, which significantly
enhances the device efficiency. The routers, which are
constantly active consumes continuous current since they are
not put into low power modes.
Achieving low power modes intelligently even in routers is
a challenging task, since the router may be asleep when the end
device requires it to relay the packets. One probable way is to
synchronize the end device and router such that they both wake
up in a particular pattern – though it would fail once the pattern
breaks. Intelligent algorithms handle such scenarios which can
9

10. sharply increase energy savings thus the usage of these devices
in wide scale applications.
REFERENCES
[1] Rex Min, Manish Bhardwaj, Seong-Hwan Cho, Eugene
Shih, Amit Sinha, Alice Wang, Anantha Chandrakasan, "LowPower Wireless Sensor Networks," VLSI Design,
International Conference on, p. 205, The 14th International
Conference on VLSI Design (VLSID '01), 2001.
[2]Jae Yeol Ha, Hong Seong Park , Sunghyun Choi, Wook
Hyun Kwon, “EHRP: Enhanced Hierarchical Routing
Protocol for Zigbee Mesh Networks,” IEEE communications
letters, December 2007.
[3]Texas Instruments, “CC2530ZNP Mini Kit Quick Start
Guide” SWRU268A, 2010.
[4]Texas Instruments, “Z-Stack – Zigbee Protocol Stack,”
[Online] http://www.ti.com/tool/z-stack, 2012.
[5]Texas Instruments, “Zigbee-PRO Network Processor,
Accelerate your Zigbee development,” SWRA312, 2010.
[6]Texas Instruments, “MSP430x2xx Family Users Guide,”
[Online] http://www.ti.com/lit/ug/slau144i/slau144i.pdf, 2012,
pp.26-41.
[7]Charles E. Perkins, Elizabeth M. Royer, “Ad-hoc Ondemand Distance Vector Routing,” 2nd IEEE workshop on
Mobile Computing systems and applications, 1997.
[8]Suyash Jain and Morten Braathen, “ Measuring Power
Consumption on Using CC2530 ZNP Mini Kit,” Texas
Instruments Application Note AN108, 2011.
[9]Texas Instruments Low Power RF Forum [Online]
http://e2e.ti.com/support/low_power_rf/f/158.aspx
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