Digi XBee DigiMesh User manual
Digi International Inc.
11001 Bren Road East
Minnetonka, MN 55343
877 912-3444 or 952 912-3444
http://www.digi.com
XBee®/XBee-PRO® DigiMesh™ 2.4 OEM RF Modules
XBee® DigiMesh 2.4 OEM RF Modules
RF Module Operation
RF Module Configuration
OEM RF Modules by Digi International
Firmware version:
8x0x XBee DigiMesh 2.4
90000991_A
9/12/2008
XBee/XBee‐PRODigiMesh2.4OEMRFModules.
©2008DigiInternational,Inc. 2
© 2008 Digi International, Inc. All rights reserved
Nopartofthecontentsofthismanualmaybetransmittedorreproducedinany
formorbyanymeanswithoutthewrittenpermissionofDigiInternational,Inc.
XBee®/XBee‐PRO®andDigiMesharetrademarksorregisteredtrademarksof
DigiInternational,Inc.
TechnicalSupport:Phone:(801)765‐9885
LiveChat:www.digi.com
Onlinesupport:http://www.digi.com/support/eservice/eservicelogin.jsp
Contents
XBee®/XBee‐PRO®DigiMesh2.4OEMRFModules
©2008DigiInternaitonal,Inc. 3
1. XBee/XBee-PRO DigiMesh 2.4 OEM RF
Modules 4
Key Features 4Worldwide Acceptance 4
Specifications 5
Mechanical Drawings 6
Mounting Considerations 6
Pin Signals 7
Electrical Characteristics 8
2. RF Module Operation 9
Serial Communications 9
UART Data Flow 9
Serial Buffers 9
Serial Flow Control 10
API Operation 11
Modes of Operation 12
Idle Mode 12
Transmit Mode 12
Receive Mode 12
Command Mode 13
3. XBee/XBee-PRO® DigiMesh 2.4 14
DigiMesh Networking 14
DigiMesh Feature Set 14
Data Transmission and Routing 14
Unicast Addressing 14
Broadcast Addressing 14
Routing 15
Route Discovery 15
Sleeping Routers 15
Operation 16
4. DigiMesh 2.4 Command Reference Tables 19
API Operation 24
API Frame Specifications 24
API Frames 25
Appendix A: Definitions 34
Appendix B: Agency Certifications 35
United States (FCC) 35
OEM Labeling Requirements 35
FCC Notices 35
FCC-Approved Antennas (2.4 GHz) 35
Europe (ETSI) 38
OEM Labeling Requirements 38
Restrictions 38
Declarations of Conformity 38
Approved Antennas 39
Canada (IC) 39
Labeling Requirements 39
Japan 39
Labeling Requirements 39
©2008DigiInternational,Inc. 4
1.XBee/XBee‐PRODigiMesh2.4OEMRF
Modules
The XBee/XBee-PRO DigiMesh 2.4 OEM RF Modules were engineered to support the unique needs
of low-cost, low-power wireless sensor networks. The modules require minimal power and provide
reliable delivery of data between remote devices.
Key Features
Worldwide Acceptance
FCC Approval (USA) Refer to Appendix A [p63] for FCC Requirements.
Systems that contain XBee®/XBee-PRO RF Modules inherit Digi Certifications.
ISM (Industrial, Scientific & Medical) 2.4 GHz frequency band
Manufactured under ISO 9001:2000 registered standards
XBee®/XBee-PRO RF Modules aare optimized for use in the United States, Canada, Australia,
Israel, Japan, and Europe. Contact Digi for complete list of government agency approvals.
Long-range Data Integrity
XBee
• Indoor/Urban: up to 100' (30 m)
• Outdoor line-of-sight: up to 300' (100m)
• Transmit Power: 1 mW (0dBm)
• Receiver Sensitivity: -92 dBm
XBee-PRO
• Indoor/Urban: up to 300' (90 m)
• Outdoor line-of-sight: up to 1 mile (1600m)
• Transmit Power: 63mW (18dBm) EIRP
• Receiver Sensitivity: -100 dBm (1% packet
error rate)
• RF Data Rate: 250,000 bps
Advanced Networking & Security
• Retries and Acknowledgements
• Self-routing, self-healing mesh networking
• DSSS (Direct Sequence Spread Spectrum)
Low Power
XBee
• TX Peak Current: 45mA
• RX Current: 50mA
• Sleep Current: <50uA
XBee-PRO
• TX Peak Current: 250mA (150mA for
international variant)
• TX Peak Current (RPSMA module only):
340mA (180mA for international variant)
• RX Current: 55mA
• Sleep Current: <50uA
Easy-to-Use
• No configuration necessary for out-of
box RF communications
• AT and API Command Modes for
configuring module parameters
• Small form factor
• Extensive command set
• Free X-CTU Software
(Testing and configuration software)
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 5
Specifications
*WhenoperatinginEurope,XBee‐PRODigiMesh2.4modulesmustoperateatorbelowatransmitpoweroutputlevelof10dBm
Customershavetwochoicesfortransmittingatorbelow10dBm:
a.OrderthestandardXBee‐PROmoduleandchangethePLcommandtoʺ0ʺ(10dBm).
b.OrdertheInternationalvariantoftheXBee‐PROmodule,whichhasamaximumtransmitoutputpowerof10dBm(@PL=4).
Additionally,EuropeanregulationsstipulateanEIRPpowermaximumof12.86dBm(19mW)fortheXBee‐PROand12.11dBm
fortheXBeewhenintegratingantennas.
**WhenoperatinginJapan,onlytheInternationalvariantoftheXBee‐PRODigiMesh2.4moduleisapprovedforuse.
SpecificationsoftheXBee/XBee‐PRODigiMesh2.4OEMRFModules
Specification XBee XBee-PRO
Performance
Indoor/Urban Range Up to 100 ft (30 m) Up to 300 ft. (90 m), up to 200 ft (60 m) International
variant
Outdoor RF line-of-sight Range Up to 300 ft (90 m) Up to 1 mile (1600 m), up to 2500 ft (750 m)
international variant
Transmit Power Output
(software selectable) 1mW (0 dBm) 63mW (18dBm)*
10mW (10 dBm) for International variant
RF Data Rate 250,000 bps 250,000 bps
Serial Interface Data Rate
(software selectable)
1200 bps - 250 kbps
(non-standard baud rates also supported)
1200 bps - 250 kbps
(non-standard baud rates also supported)
Receiver Sensitivity -92 dBm (1% packet error rate) -100 dBm (1% packet error rate)
Power Requirements
Supply Voltage 2.8 – 3.4 V 2.8 – 3.4 V
Transmit Current (peak) 45mA (@ 3.3 V)
250mA (@3.3 V) (150mA for international variant)
RPSMA module only: 340mA (@3.3 V) (180mA for
international variant)
Idle / Receive Current (typical) 50mA (@ 3.3 V) 55mA (@ 3.3 V)
Power-down Current < 50 µA < 50 µA
General
Operating Frequency ISM 2.4 GHz ISM 2.4 GHz
Dimensions 0.960” x 1.087” (2.438cm x 2.761cm) 0.960” x 1.297” (2.438cm x 3.294cm)
Operating Temperature -40 to 85º C (industrial) -40 to 85º C (industrial)
Antenna Options Integrated whip, Chip, U.Fl Connector, RPSMA
Connector
Integrated whip, Chip, U.Fl Connector, RPSMA
Connector
Networking & Security
Supported Network Topologies Point-to-point, Point-to-multipoint & Peer-to-peer
Number of Channels
(software selectable) 16 Direct Sequence Channels 12 Direct Sequence Channels
Addressing Options PAN ID, Channel and Addresses PAN ID, Channel and Addresses
Agency Approvals
United States (FCC Part 15.247) OUR-XBEE OUR-XBEEPRO
Industry Canada (IC) 4214A XBEE 4214A XBEEPRO
Europe (CE) ETSI ETSI (Max. 10 dBm transmit power output)*
Japan R201WW07215214 R201WW08215111 (Max. 10 dBm transmit power
output)**
Austraila C-Tick C-Tick
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 6
Mechanical Drawings
Antenna Options: The ranges specified are typical when using the integrated Whip (1.5 dBi) and Dipole (2.1 dBi) anten-
nas. The Chip antenna option provides advantages in its form factor; however, it typically yields shorter range than the
Whip and Dipole antenna options when transmitting outdoors.For more information, refer to the "XBee Antennas" Knowl-
edgebase Article located on Digi's Support Web site
MechanicaldrawingsoftheXBee/XBee‐PRODigiMesh2.4OEMRFModules
TheXBeeandXBee‐PRORFModulesarepin‐for‐pincompatible.
Mounting Considerations
The XBee/XBee-Pro DigiMesh 2.4 RF Module (through-hole) was designed to mount into a
receptacle (socket) and therefore does not require any soldering when mounting it to a board. The
Development Kits contain RS-232 and USB interface boards which use two 20-pin receptacles to
receive modules.
XBee/XBee‐ProDigiMesh2.4ModuleMountingtoanRS‐232InterfaceBoard.
The receptacles used on Digi development boards are manufactured by Century Interconnect.
Several other manufacturers provide comparable mounting solutions; however, Digi currently uses
the following receptacles:
• Through-hole single-row receptacles -
Samtec P/N: MMS-110-01-L-SV (or equivalent)
• Surface-mount double-row receptacles -
Century Interconnect P/N: CPRMSL20-D-0-1 (or equivalent)
• Surface-mount single-row receptacles -
Samtec P/N: SMM-110-02-SM-S
Digi also recommends printing an outline of the module on the board to indicate the orientation the
module should be mounted.
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 7
Pin Signals
XBee/XBee‐PRODigiMesh2.4RFModulePin
Numbers
(topsidesshown‐shieldsonbottom)
*Functionisnotsupportedatthetimeofthisrelease
Design Notes:
• Minimum connections: VCC, GND, DOUT & DIN
• Minimum connections for updating firmware: VCC, GND, DIN, DOUT, RTS & DTR
• Signal Direction is specified with respect to the module
• Module includes a 50k Ω pull-up resistor attached to RESET
• Several of the input pull-ups can be configured using the PR command
• Unused pins should be left disconnected
Table3‐01. PinAssignmentsfortheXBee/XBee‐PRO2.4DigiMeshModules
(Low‐assertedsignalsaredistinguishedwithahorizontallineabovesignalname.)
Pin # Name Direction Description
1 VCC - Power supply
2 DOUT Output UART Data Out
3 DIN / CONFIG Input UART Data In
4 DO8* Output Digital Output 8
5RESET Input Module Reset (reset pulse must be at least 200 ns)
6 PWM0 / RSSI Output PWM Output 0 / RX Signal Strength Indicator
7 PWM1 Output PWM Output 1
8 [reserved] - Do not connect
9DTR
/ SLEEP_RQ / DI8 Input Pin Sleep Control Line or Digital Input 8
10 GND - Ground
11 AD4 / DIO4 Either Analog Input 4 or Digital I/O 4
12 CTS / DIO7 Either Clear-to-Send Flow Control or Digital I/O 7
13 ON / SLEEP Output Module Status Indicator
14 VREF Input Voltage Reference for A/D Inputs
15 Associate / AD5 / DIO5 Either Associated Indicator, Analog Input 5 or Digital I/O 5
16 RTS / AD6 / DIO6 Either Request-to-Send Flow Control, Analog Input 6 or Digital I/O 6
17 AD3 / DIO3 Either Analog Input 3 or Digital I/O 3
18 AD2 / DIO2 Either Analog Input 2 or Digital I/O 2
19 AD1 / DIO1 Either Analog Input 1 or Digital I/O 1
20 AD0 / DIO0 Either Analog Input 0 or Digital I/O 0
Pin 1
Pin 10
Pin 1
Pin 10
Pin 20
Pin 11
Pin 20
Pin 11
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 8
Electrical Characteristics
Table3‐02. DCCharacteristics(VCC=2.8‐3.4VDC)
Symbol Characteristic Condition Min Typical Max Unit
VIL Input Low Voltage All Digital Inputs - - 0.35 * VCC V
VIH Input High Voltage All Digital Inputs 0.7 * VCC - - V
VOL Output Low Voltage IOL = 2 mA, VCC >= 2.7 V --0.5V
VOH Output High Voltage IOH = -2 mA, VCC >= 2.7 V VCC - 0.5 - - V
IIIN Input Leakage Current VIN = VCC or GND, all inputs, per pin - 0.025 1 µA
IIOZ High Impedance Leakage Current VIN = VCC or GND, all I/O High-Z, per pin - 0.025 1 µA
TX Transmit Current VCC = 3.3 V - 45
(XBee)
215, 140
(PRO,
Int)
-mA
RX Receive Current VCC = 3.3 V - 50
(XBee)
55
(PRO) -mA
PWR-DWN Power-down Current SM parameter = 1 - < 10 - µA
Table3‐03. ADCCharacteristics(Operating)
Symbol Characteristic Condition Min Typical Max Unit
VREFH VREF - Analog-to-Digital converter
reference range 2.08 - VDDAD V
IREF VREF - Reference Supply Current Enabled - 200 - µA
Disabled or Sleep Mode - < 0.01 0.02 µA
VINDC Analog Input Voltage1
1. Maximumelectricaloperatingrange,notvalidconversionrange.
VSSAD - 0.3 -VDDAD + 0.3 V
Table3‐04. ADCTiming/PerformanceCharacteristics1
1. AllACCURACYnumbersarebasedonprocessorandsystembeinginWAITstate(verylittleactivityandnoIOswitching)
andthatadequatelow‐passfilteringispresentonanaloginputpins(filterwith0.01μFto0.1μFcapacitorbetweenanalog
inputandVREFL).Failuretoobservetheseguidelinesmayresultinsystemormicrocontrollernoisecausingaccuracyerrors
whichwillvarybasedonboardlayoutandthetypeandmagnitudeoftheactivity.
Datatransmissionandreceptionduringdataconversionmaycausesomedegradationofthesespecifications,dependingon
thenumberandtimingofpackets.ItisadvisabletotesttheADCsinyourinstallationifbestaccuracyisrequired.
Symbol Characteristic Condition Min Typical Max Unit
RAS Source Impedance at Input2
2. RASistherealportionoftheimpedanceofthenetworkdrivingtheanaloginputpin.Valuesgreaterthanthisamountmay
notfullychargetheinputcircuitryoftheATDresultinginaccuracyerror.
--10 k
VAIN Analog Input Voltage3
3. AnaloginputmustbebetweenVREFLandVREFHforvalidconversion.ValuesgreaterthanVREFHwillconvertto$3FF.
VREFL VREFH V
RES Ideal Resolution (1 LSB)4
4. Theresolutionistheidealstepsizeor1LSB=(VREFH–VREFL)/1024
2.08V < VDDAD < 3.6V 2.031 - 3.516 mV
DNL Differential Non-linearity5
5. Differentialnon‐linearityisthedifferencebetweenthecurrentcodewidthandtheidealcodewidth(1LSB).Thecurrent
codewidthisthedifferenceinthetransitionvoltagestoandfromthecurrentcode.
- ±0.5 ±1.0 LSB
INL Integral Non-linearity6
6. Integralnon‐linearityisthedifferencebetweenthetransitionvoltagetothecurrentcodeandtheadjustedidealtransition
voltageforthecurrentcode.Theadjustedidealtransitionvoltageis(CurrentCode–1/2)*(1/((VREFH+EFS)–(VREFL+EZS))).
- ±0.5 ±1.0 LSB
EZS Zero-scale Error7
7. Zero‐scaleerroristhedifferencebetweenthetransitiontothefirstvalidcodeandtheidealtransitiontothatcode.The
Idealtransitionvoltagetoagivencodeis(Code–1/2)*(1/(VREFH–VREFL)).
- ±0.4 ±1.0 LSB
FFS Full-scale Error8
8. Full‐scaleerroristhedifferencebetweenthetransitiontothelastvalidcodeandtheidealtransitiontothatcode.Theideal
transitionvoltagetoagivencodeis(Code–1/2)*(1/(VREFH–VREFL)).
- ±0.4 ±1.0 LSB
EIL Input Leakage Error9
9. Inputleakageerroriserrorduetoinputleakageacrosstherealportionoftheimpedanceofthenetworkdrivingtheanalog
pin.Reducingtheimpedanceofthenetworkreducesthiserror.
- ±0.05 ±5.0 LSB
ETU Total Unadjusted Error10
10.Totalunadjustederroristhedifferencebetweenthetransitionvoltagetothecurrentcodeandtheidealstraight‐linetrans‐
ferfunction.Thismeasureoferrorincludesinherentquantizationerror(1/2LSB)andcircuiterror(differential,integral,zero‐
scale,andfull‐scale)error.ThespecifiedvalueofETUassumeszeroEIL(noleakageorzerorealsourceimpedance).
- ±1.1 ±2.5 LSB
©2008DigiInternational,Inc. 9
2.RFModuleOperation
Serial Communications
The XBee/XBee-PRO 2.4 DigiMesh OEM RF Modules interface to a host device through a logic-level
asynchronous serial port. Through its serial port, the module can communicate with any logic and
voltage compatible UART; or through a level translator to any serial device (For example: Through
a Digi proprietary RS-232 or USB interface board).
UART Data Flow
Devices that have a UART interface can connect directly to the pins of the RF module as shown in
the figure below.
SystemDataFlowDiagraminaUART‐interfacedenvironment
(Low‐assertedsignalsdistinguishedwithhorizontallineoversignalname.)
Serial Data
Data enters the module UART through the DIN (pin 3) as an asynchronous serial signal. The signal
should idle high when no data is being transmitted.
Each data byte consists of a start bit (low), 8 data bits (least significant bit first) and a stop bit
(high). The following figure illustrates the serial bit pattern of data passing through the module.
UARTdatapacket0x1F(decimalnumberʺ31ʺ)astransmittedthroughtheRFmodule
ExampleDataFormatis8‐N‐1(bits‐parity‐#ofstopbits)
The module UART performs tasks, such as timing and parity checking, that are needed for data
communications. Serial communications depend on the two UARTs to be configured with
compatible settings (baud rate, parity, start bits, stop bits, data bits).
Serial Buffers
The XBee-PRO modules maintain buffers to collect received serial and RF data, which is illustrated
in the figure below. The serial receive buffer collects incoming serial characters and holds them
until they can be processed. The serial transmit buffer collects data that is received via the RF link
that will be transmitted out the UART.
Microcontroller Microcontroller
XBee
Module
XBee
Module
CMOS Logic (3.0-3.6V)
DOUT (data out)
DIN (data in)
CTS
RTS
CMOS Logic (3.0-3.6V)
DOUT (data out)
DIN (data in)
CTS
RTS
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 10
InternalDataFlowDiagram
Serial Receive Buffer
When serial data enters the RF module through the DIN Pin (pin 3), the data is stored in the serial
receive buffer until it can be processed. Under certain conditions, the module may not be able to
process data in the serial receive buffer immediately. If large amounts of serial data are sent to
the module, CTS flow control may be required to avoid overflowing the serial receive buffer.
Cases in which the serial receive buffer may become full and possibly overflow:
1. If the module is receiving a continuous stream of RF data, the data in the serial receive buffer
will not be transmitted until the module is no longer receiving RF data.
2. If the module is transmitting an RF data packet, the module may need to discover the
destination address or establish a route to the destination. After transmitting the data, the module
may need to retransmit the data if an acknowledgment is not received, or if the transmission is a
broadcast. These issues could delay the processing of data in the serial receive buffer.
Serial Transmit Buffer
When RF data is received, the data is moved into the serial transmit buffer and is sent out the
serial port. If the serial transmit buffer becomes full enough such that all data in a received RF
packet won’t fit in the serial transmit buffer, the entire RF data packet is dropped.
Cases in which the serial transmit buffer may become full resulting in dropped RF
packets
If the RF data rate is set higher than the interface data rate of the module, the module could
receive data faster than it can send the data to the host.
If the host does not allow the module to transmit data out from the serial transmit buffer because
of being held off by hardware flow control.
Serial Flow Control
The RTS and CTS module pins can be used to provide RTS and/or CTS flow control. CTS flow
control provides an indication to the host to stop sending serial data to the module. RTS flow
control allows the host to signal the module to not send data in the serial transmit buffer out the
UART. RTS and CTS flow control are enabled using the D6 and D7 commands.
CTS Flow Control
If CTS flow control is enabled (D7 command), when the serial receive buffer is is filled with FT
bytes, the module de-asserts CTS (sets it high) to signal to the host device to stop sending serial
data. CTS is re-asserted when less than FT - 16 bytes are in the UART receive buffer.
Serial
Receiver
Buffer
RF TX
Buffer Transmitter
RF Switch
Antenna
Port
Receiver
Serial Transmit
Buffer
RF RX
Buffer
Processor
GND
DIN
VCC
DOUT
CTS
RTS
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 11
RTS Flow Control
If flow RTS control is enabled (D6 command), data in the serial transmit buffer will not be sent
out the DOUT pin as long as RTS is de-asserted (set high). The host device should not de-assert
RTS for long periods of time to avoid filling the serial transmit buffer. If an RF data packet is
received, and the serial transmit buffer does not have enough space for all of the data bytes, the
entire RF data packet will be discarded.
Transparent Operation
When operating in Transparent Operation, the modules act as a serial line replacement. All UART
data received through the DIN pin is queued up for RF transmission. When RF data is received, the
data is sent out the DOUT pin. The module configuration parameters are configured using the AT
command mode interface. (See RF Module Operation --> Command Mode.)
Serial-to-RF Packetization
Data is buffered in the serial receive buffer until one of the following causes the data to be
packetized and transmitted:
No serial characters are received for the amount of time determined by the RO (Packetization
Timeout) parameter. If RO = 0, packetization begins when a character is received.
The maximum number of characters that will fit (73) in an RF packet is received.
The Command Mode Sequence (GT + CC + GT) is received. Any character buffered in the serial
receive buffer before the sequence is transmitted.
API Operation
API (Application Programming Interface) Operation is an alternative to the default Transparent
Operation. The frame-based API extends the level to which a host application can interact with the
networking capabilities of the module. When in API mode, all data entering and leaving the
module is contained in frames that define operations or events within the module.
Transmit Data Frames (received through the DIN pin (pin 3)) include:
• RF Transmit Data Frame
• Command Frame (equivalent to AT commands)
Receive Data Frames (sent out the DOUT pin (pin 2)) include:
• RF-received data frame
• Command response
• Event notifications such as reset, etc.
The API provides alternative means of configuring modules and routing data at the host
application layer. A host application can send data frames to the module that contain address and
payload information instead of using command mode to modify addresses. The module will send
data frames to the application containing status packets; as well as source, and payload
information from received data packets.
The API operation option facilitates many operations such as the examples cited below:
->Transmitting data to multiple destinations without entering Command Mode
->Receive success/failure status of each transmitted RF packet
->Identify the source address of each received packet
To implement API operations, refer to the API Operation chapter 6.
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 12
Modes of Operation
Idle Mode
When not receiving or transmitting data, the RF module is in Idle Mode. During Idle Mode, the RF
module is also checking for valid RF data. The module shifts into the other modes of operation
under the following conditions:
• Transmit Mode (Serial data in the serial receive buffer is ready to be packetized)
• Receive Mode (Valid RF data is received through the antenna)
• Command Mode (Command Mode Sequence is issued)
Transmit Mode
When serial data is received and is ready for packetization, the RF module will exit Idle Mode and
attempt to transmit the data. The destination address determines which node(s) will receive the
data.
If a route is not known, route discovery will take place for the purpose of establishing a route to
the destination node. If a module with a matching network address is not discovered, the packet is
discarded. The data will be transmitted once a route is established. If route discovery fails to
establish a route, the packet will be discarded.
TransmitModeSequence
When data is transmitted from one node to another, a network-level acknowledgement is
transmitted back across the established route to the source node. This acknowledgement packet
indicates to the source node that the data packet was received by the destination node. If a
network acknowledgement is not received, the source node will re-transmit the data. See Data
Transmission and Routing in chapter 3 for more information.
Receive Mode
If a valid RF packet is received, the data is transferred to the serial transmit buffer
Data Discarded
Successful
Transmission
New
Transmission
Route Known?
Route Discovered?
Route Discovery
Transmit Data
Idle Mode
No
Yes
No
Yes
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 13
Command Mode
To modify or read RF Module parameters, the module must first enter into Command Mode - a
state in which incoming serial characters are interpreted as commands. Refer to the API Mode
section for an alternate means of configuring modules.
AT Command Mode
To Enter AT Command Mode:
Send the 3-character command sequence “+++” and observe guard times before and after the
command characters. [Refer to the “Default AT Command Mode Sequence” below.]
Default AT Command Mode Sequence (for transition to Command Mode):
• No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
• Input three plus characters (“+++”) within one second [CC (Command Sequence Character)
parameter = 0x2B.]
• No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
All of the parameter values in the sequence can be modified to reflect user preferences.
NOTE: Failure to enter AT Command Mode is most commonly due to baud rate mismatch. Ensure the
‘Baud’ setting on the “PC Settings” tab matches the interface data rate of the RF module. By default,
the BD parameter = 3 (9600 bps).
To Send AT Commands:
Send AT commands and parameters using the syntax shown below.
SyntaxforsendingATCommands
To read a parameter value stored in the RF module’s register, omit the parameter field.
The preceding example would change the RF module Destination Address (Low) to “0x1F”. To
store the new value to non-volatile (long term) memory, subsequently send the WR (Write)
command.
For modified parameter values to persist in the module’s registry after a reset, changes must be
saved to non-volatile memory using the WR (Write) Command. Otherwise, parameters are
restored to previously saved values after the module is reset.
System Response. When a command is sent to the module, the module will parse and execute
the command. Upon successful execution of a command, the module returns an “OK” message. If
execution of a command results in an error, the module returns an “ERROR” message.
To Exit AT Command Mode:
1. Send the ATCN (Exit Command Mode) command (followed by a carriage return).
[OR]
2. If no valid AT Commands are received within the time specified by CT (Command Mode
Timeout) Command, the RF module automatically returns to Idle Mode.
For an example of programming the RF module using AT Commands and descriptions of each config-
urable parameter, refer to the "Command Reference Tables" chapter.
Sleep Mode
Sleep mode allows the module to enter a low power state. See chapter 3 for more information.
©2008DigiInternational,Inc. 14
3.XBee/XBee‐PRO®DigiMesh2.4
DigiMesh Networking
Mesh networking allows messages to be routed through several different nodes to a final
destination. DigiMesh firmware allows OEMs and system integrators to bolster their networks with
the self-healing attributes of mesh networking. In the event that one RF connection between
nodes is lost (due to power-loss, environmental obstructions, etc.) critical data can still reach its
destination due to the mesh networking capabilities embedded inside the modules.
DigiMesh Feature Set
DigiMesh contains the following features
•Self-healing
Any node may enter or leave the network at any time without causing the network as a whole
to fail.
•Peer-to-peer architecture
No hierarchy and no parent-child relationships are needed.
•Quiet Protocol
Routing overhead will be reduced by using a reactive protocol similar to AODV.
•Route Discovery
Rather than maintaining a network map, routes will be discovered and created only when
needed.
•Selective acknowledgements
Only the destination node will reply to route requests.
•Reliable delivery
Reliable delivery of data is accomplished by means of acknowledgements.
•Sleep Modes
Low power sleep modes with synchronized wake are supported, with variable sleep and wake
times.
Data Transmission and Routing
Unicast Addressing
When transmitting while using Unicast communications, reliable delivery of data is accomplished
using retries and acknowledgements. The number of retries is determined by the NR (Network
Retries) parameter. RF data packets are sent up to NR + 1 times and ACKs (acknowledgements)
are transmitted by the receiving node upon receipt. If a network ACK is not received within the
time it would take for a packet to traverse the network twice, a retransmission occurs.
To send Unicast messages, set the DH and DL on the transmitting module to match the
corresponding SH and SL parameter values on the receiving module.
Broadcast Addressing
Broadcast transmissions will be received and repeated by all nodes in the network. Because ACKs
are not used the originating node will send the broadcast four times. Essentially the extra
transmissions become automatic retries without acknowledgments. This will result in all nodes
repeating the transmission four times as well. In order to avoid RF packet collisions, a random
delay is inserted before each node relays the broadcast message. (See NN parameter for details
on changing this random delay time.) Sending frequent broadcast transmissions can quickly
reduce the available network bandwidth and as such should be used sparingly.
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 15
Routing
A module within a mesh network is able to determine reliable routes using a routing algorithm and
table. The routing algorithm uses a reactive method derived from AODV (Ad-hoc On-demand
Distance Vector). An associative routing table is used to map a destination node address with its
next hop. By sending a message to the next hop address, either the message will reach its
destination or be forwarded to an intermediate node which will route the message on to its
destination. A message with a Broadcast address is broadcast to all neighbors. All receiving
neighbors will rebroadcast the message and eventually the message will reach all corners of the
network. Packet tracking prevents a node from resending a broadcast message twice.
Route Discovery
If the source node doesn’t have a route to the requested destination, the packet is queued to
await a route discovery (RD) process. This process is also used when a route fails. A route fails
when the source node uses up its network retries without ever receiving an ACK. This results in
the source node initiating RD.
RD begins by the source node broadcasting a route request (RREQ). Any node that receives the
RREQ that is not the ultimate destination is called an intermediate node.
Intermediate nodes may either drop or forward a RREQ, depending on whether the new RREQ has
a better route back to the source node. If so, information from the RREQ is saved and the RREQ is
updated and broadcast. When the ultimate destination receives the RREQ, it unicasts a route reply
(RREP) back to the source node along the path of the RREQ. This is done regardless of route
quality and regardless of how many times an RREQ has been seen before.
This allows the source node to receive multiple route replies. The source node selects the route
with the best round trip route quality, which it will use for the queued packet and for subsequent
packets with the same destination address.
Sleeping Routers
Sleeping routers under DigiMesh allows for all nodes in the network to synchronize their sleep and
wake times. All synchronized nodes enter and exit a low power state at the same time. This
forms a cyclic sleeping network. Nodes synchronize by receiving a special RF packet called a synch
message which is sent by a sleep coordinator. Any node in the network can become a sleep
coordinator through a process called nomination. The sleep coordinator will send one synch
message at the beginning of each wake period. The synch message being a broadcast packet is
repeated by every node in the network.
There are two modes of operation:
SM0 - Normal (default)
SM4 - Cyclic Sleep (low power)
A network should consist of nodes operating in the same mode. Mesh route discovery, and thereby
routing, is incompatible between nodes operating in different modes. However, during network
setup and maintenance, a mix of nodes is useful, and can be tolerated provided route discovery is
not attempted.
Sleep Mode
A node in cyclic sleep mode sleeps for a programmed time, wakes in unison with other nodes,
exchanges data and synch messages, and then returns to sleep. While asleep, it cannot receive RF
messages, neither will it read commands from the UART port. Sleep and wake times are set by SP
and ST respectively. These parameters must be set the same for all nodes in the network. If D7 =
1 (CTS Flow control) CTS is de-asserted while asleep, and asserted while awake.
An unsynched sleeping node, newly powered, will wake and poll for a synch message and then
return to sleep, repeating the cycle until it becomes synched by receiving a synch message. Once
synched, the node will wake to exchange messages for the programmed time interval and then
return to sleep.
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 16
Normal Mode
Normal mode is the default mode for a newly powered on node. In this mode a node will not sleep,
but will synchronize to a sleeping network. When synchronized a normal node can aid in setting up
and maintaining a synchronized network by responding to synch message requests from nodes in
cyclic sleep mode (SM4) by sending a special unicast synch message.
Note: Although a normal node can synchronize to a sleeping network, it will not defer data
transmission during sleep. A normal mode node synchronized to a sleeping network can be used
for maintenance purposes such as adding new nodes to the sleeping networks.
Operation
Nomination
Nomination is the process where a node becomes a sleep coordinator at the start of a sleeping
network or in the event a sleep coordinator fails as a replacement. This process is automatic with
any sleeping node being eligible to become the sleep coordinator for the network. This process can
be managed through SO by allowing a node to alter the algorithm used for nomination giving the
node a greater chance to become the sleep coordinator. This option is designed for maintenance
purposes and is not necessary for cyclic sleep operation.
If the node has the preferred sleep coordinator option-enabled (SO=1), then it will poll during its
first cycle for a synch message. If it becomes synched by receiving a synch message, it will cycle
back to sleep and will not become the sleep coordinator. If it does not become synched during that
first cycle, then it will nominate itself as the sleep coordinator and will start sending synch
messages at the start of its second cycle.
Any sleeping node, if it does not receive a message for three cycles, may nominate itself to act as
a replacement sleep coordinator. Depending on the platform and other configured options, such a
node will eventually nominate itself after a number of cycles without a synch. If preferred sleep
coordinator option is enabled, a sleeping node will nominate itself immediately after one cycle
without a synch message.
Election
If multiple nodes nominate themselves at the same time, then an election will take place to
resolve which node will function as the network's sleep coordinator. A node will disable synching if
it receives a synch message from a senior node. A node running in normal mode (with preferred
sleep coordinator option enabled) is senior to any node operating in sleep mode. A node with the
largest MAC address value is senior to any other node operating in the same mode.
Preferred Sleep Coordinator Option
The preferred sleep coordinator option is
• SO = 1 - preferred sleep coordinator.
Enabling this bit will cause a node operating in normal mode to act as a sleep coordinator or cause
a sleeping node to nominate itself after one cycle without receiving a synch message. Setting a
normal mode node to act as a sleep coordinator can be used to start a network. After the network
is set up the normal node can be turned off if no longer needed. A sleeping node, after several
cycles, will elect itself as the sleep coordinator. Designating a cyclic sleep mode node as a
preferred sleep coordinator is useful where a node or nodes are conveniently positioned for
maintenance. It is also useful when enabled on a centrally located node to minimize the number of
hops a synch message must take to get across the network.
Programming Sleep Time Intervals
The commands for programming sleep time intervals are
• SP - sleep time
• ST - wake time.
Starting a Sleeping Network
By default, all new nodes operate in normal mode. To start a sleeping network, follow these steps:
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 17
1. Enable the preferred sleep coordinator on one of the nodes, and set its SP and ST to their
default values. The idea is to set these values short enough so that commands can be sent quickly
throughout the network which will set a longer sleep cycle.
2. Next, power on the other nodes within range of the sleep coordinator.
The nodes will receive the synch message and synchronize themselves to the short cycle SP and
ST.
3. Configure one or more of the nodes with the preferred sleep coordinator option.
Since they are already synched and in range of the sleep coordinator, they will not nominate
themselves.
4. Configure the nodes which do not have the preferred sleep coordinator option enabled with
SM4, putting them into cyclic sleep mode.
5. Reconfigure the sleep coordinator to the SP and ST values selected for the deployed network.
6. Wait a cycle for the sleeping nodes to synch themselves to the new SP and ST values.
7. Deploy the sleeping nodes to their positions.
8. Reconfigure the sleep coordinator node with SM4 to operate in sleep node and deploy the node.
Maintaining a Network
Use the following tasks to help maintain a network: adding a node--both normal and sleeping,
changing sleep parameters, and rejoining subnets operating out of synch.
Adding a Normal Node
To add a node to an existing network:
Power on the new node and deploy it within range of a node in the network. If there is a sleep
coordinator in the network, the new node will pick up the message when it is broadcast. Through
the synch message it will become aware of the network's wake and sleep time intervals, and the
time the next cycle will begin.
Adding a Sleeping Node
Adding a sleeping node to an existing network of sleeping nodes is easier if you use a node
operating in normal mode as an assist.
1. Set up a normal node in range of another node in the network.
2. Wait a cycle time for the normal node to synch with the network.
3. Configure the sleeping node with the command ATSM4, write the mode to the configuration
with ATWR, and reset the node.
4. Place the new sleeping node in range of the normal node. As the sleeping node wakes, it
realizes it is unsynched, and will request a synch message. The normal node will then respond
with a special unicast synch special unicast synch message. The new sleeping node will adjust its
configuration to match the synch message's contents, and a cycle later will wake in synch with the
rest of the sleeping network.
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 18
Changing Sleep Parameters
Use the following steps to change sleep parameters:
1. Enter the SP command with the sleep time interval represented in units of 10 msec.
2. Enter the ST command with the wake time interval represented in units of 1 msec.
3. Verify the values of the SP and ST commands.
Note: the value of the ST configuration parameter will be automatically adjusted to a minimum
effective value if the value of SP is increased enough. However, ST will not be automatically
adjusted downwards should the value of SP be decreased. Enter the apply changes command AC.
At the start of the next cycle, a special overriding synch message will be broadcast across the
network. It will override any synch message coming from any sleep coordinator. Then, a cycle
later, the network will wake and operate according to the new ST and SP values.
Rejoining Subnets
Mesh networks get their robustness from taking advantage of routing redundancies which may be
available in a network. It is recommended to architect the network with redundant mesh nodes to
increase robustness. If a scenario exists such that the only route connecting a subnet to the rest of
the network depends on a single node, and that node fails--or the wireless link fails due to
changing environmental conditions (catastrophic failure condition), then multiple subnets may
arise while using the same wake and sleep intervals, but out of phase with each other due to clock
drift. The first task is to repair, replace, and strengthen the weak link with new and/or redundant
nodes so this problem doesn't arise again. The second task is to get the subnets back in phase
(rejoin subnets).
To get the subnets back in phase, follow these steps:
1. Power up a node in normal mode, and position it next to a node in the subnet you want to use
as a reference.
2. Wait a cycle (plus a bit more for safety margin) for it to synch with the network.
3. Enable its preferred sleep coordinator option. This node will now become the sleep coordinator
for the network. A synch from a normal node overrides synch messages from any sleeping node
and will cause any sleep coordinator node to disable its own synch message.
To place each out-of-phase sleeping node, follow these steps:
1. Place the sleep coordinator node in range of the sleeping node and toggle power for the
sleeping node off and back on.
2. When the sleeping coordinator node powers up, it sees that it is out of synch, and requests a
synch message. The sleep coordinator node will receive the request and transmit a special unicast
synch response. The sleeping node will return to sleep and wake again in synch with the rest of
the network.
3. Power down and store away the normal node for safe keeping.
©2008DigiInternational,Inc. 19
4.DigiMesh2.4CommandReferenceTables
Special
Addressing
Serial Interfacing (I/O)
SpecialCommands
AT
Command Name and Description Parameter Range Default
WR
Write. Write parameter values to non-volatile memory so that parameter modifications
persist through subsequent resets.
Note: Once WR is issued, no additional characters should be sent to the module until
after the "OK\r" response is received.
-- --
RE Restore Defaults. Restore module parameters to factory defaults. -- --
FR Software Reset. Reset module. Responds immediately with an “OK” then performs a
reset 100ms later. -- --
AC Apply Changes. Immediately applies new settings without exiting command mode. -- --
VL Version Long. Shows detailed version information including application build date and
time. -- --
AddressingCommands)
AT
Command Name and Description Parameter Range Default
DH Destination Address High. Set/Get the upper 32 bits of the 64-bit destination address.
When combined with DL, it defines the destination address used for transmission. 0 to 0xFFFFFFFF 0
DL Destination Address Low. Set/Get the lower 32 bits of the 64-bit destination address.
When combined with DH, DL defines the destination address used for transmission. 0 to 0xFFFFFFFF 0x0000FFFF
SH
Serial Number High. Read high 32 bits of the RF module's unique IEEE 64-bit
address. 64-bit source address is always enabled. This value is read-only and it never
changes
0x-0xFFFFFFFF Factory
SL
Serial Number Low. Read low 32 bits of the RF module's unique IEEE 64-bit address.
64-bit source address is always enabled . This is read only and it is also the serial
number of the node. .
0 to 0xFFFFFFFF Factory
NI
Node Identifier. Stores a string identifier. The register only accepts printable ASCII
data. In AT Command Mode, a string can not start with a space. A carriage return ends
the command. Command will automatically end when maximum bytes for the string
have been entered. This string is returned as part of the ND (Node Discover) command.
This identifier is also used with the DN (Destination Node) command.
20-Byte printable
ASCII string Space Character
SerialInterfacingCommands
AT
Command Name and Description Parameter Range Default
AP
API mode. Set or read the API mode of the radio. The following settings are allowed:
0API mode is off. All UART input and output is raw data and packets are delineated
using the RO parameter.
1API mode is on. All UART input and output data is packetized in the API format,
without escape sequences.
2API mode is on with escaped sequences inserted to allow for control characters (XON,
XOFF, escape, and the 0x7e delimiter to be passed as data.
0, 1, or 2 0
AO
API Output Format. Enables different API output frames. Options include:
0Standard Data Frames (0x90 for RF rx)
1Explicit Addressing Data Frames (0x91 for RF rx)
0, 1 0
BD
Baud rate. Set or read serial interface rate (speed for data transfer between radio
modem and host). Values from 0-8 select preset standard rates. Values at 0x7A and
above select the actual baud rate. Baud rates above 250,00 bps are not supported.The
values from 0 to 8 are interpreted as follows:
0- 1,200bps 3 - 9,600bps 6- 57,600bps
1- 2,400bps 4- 19,200bps 7- 115,200bps
2- 4,800bps 5 - 38,400bps 8- 230,400bps
Note that exact baud rates cannot be achieved for 115,200 and 230,400 bps and are
111,111 and 250,000 respectively.
0 to 8, and 0x7a to
0x1C9C38
0x03 (9600
bps)
RO
Packetization Timeout. Set/Read number of character times of inter-character silence
required before packetization. Set (RO=0) to transmit characters as they arrive instead of
buffering them into one RF packet.
0 - 0xFF
[x character times] 3
XBee/XBee‐PRODigiMesh2.4OEMRFModules
©2008DigiInternational,Inc. 20
I/O Commands
FT
Flow Control Threshhold. Set or read flow control threshhold. De-assert CTS and/or
send XOFF when FT bytes are in the UART receive buffer. Re-assert CTS when less
than FT - 16 bytes are in the UART receive buffer.
0x11 to 0xEE 0xbe = 190
NB
Parity. Set or read parity settings for UART communications. The values from 0 to 4 are
interpreted as follows:
0No parity 3Forced high parity
1Even parity 4Forced low parity
2 Odd parity
0 to 4 0 (No parity)
D7
DIO7 Configuration. Configure options for the DIO7 line of the module. Options include:
0 = Input, unmonitored
1 = CTS flow control
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
6 = RS-485 Tx enable, low TX (0V on transmit, high when idle)
7 = RS-485 Tx enable, high TX (high on transmit, 0V when idle)
0-1, 3-7 0
D6
DIO6 Configuration. Configure options for the DIO6 line of the module. Options include:
0 = Input, unmonitored
1 = RTS flow control
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
0-1, 3-5 0
D5
AD5/DIO5 Configuration. Configure options for the AD5/DIO5 line of the module.
Options include:
0 = Input, unmonitored
1 = Power LED output
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
0-1, 3-5 1
I/OCommands
AT
Command Name and Description Parameter Range Default
P0
DIO10/PWM0 Configuration. Configure options for the DIO10/PWM0 line of the
module. Options include:
0 = Input, unmonitored
1 = RSSI
2 = PWM0
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
0-5 1
P1
DIO11/PWM1 Configuration. Configure options for the DIO11/PWM1 line of the
module. Options include:
0 = Input, unmonitored
2 = PWM1
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
0, 2-5 0
P2
DIO12 Configuration. Configure options for the DIO12 line of the module. Options
include:
0 = Input, unmonitored
3 = Digital input, monitored
4 = Digital output low
5 = Digital output high
0, 3-5 0
RP RSSI PWM Timer. Time RSSI signal will be output after last transmission. When RP =
0xFF, output will always be on. 0 - 0xFF [x 100 ms] 2032 3.2
seconds)
SerialInterfacingCommands
AT
Command Name and Description Parameter Range Default
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