Digi XBee 868LP User Manual
XBee® 868LP
Radio Frequency (RF) Modules
User Guide
Revision history—90002126
Revision Date Description
P July 2016 Updated pushbutton drawing and ISO spec number.
R October2016 Converted to the new MadCap Flare format with minor updates and
added the information from the XBee 868LP Getting Started Guide
(90002127).
S June 2017 Modified regulatory and certification information as required by RED
(Radio Equipment Directive).
T May 2018 Added note on range estimation.
U March 2019 Added a receiver category to Performance specifications.
Trademarks and copyright
Digi, Digi International, and the Digi logo are trademarks or registered trademarks in the United
States and other countries worldwide. All other trademarks mentioned in this document are the
property of their respective owners.
© 2018 Digi International Inc. All rights reserved.
Disclaimers
Information in this document is subject to change without notice and does not represent a
commitment on the part of Digi International. Digi provides this document “as is,” without warranty of
any kind, expressed or implied, including, but not limited to, the implied warranties of fitness or
merchantability for a particular purpose. Digi may make improvements and/or changes in this manual
or in the product(s) and/or the program(s) described in this manual at any time.
Warranty
To view product warranty information, go to the following website:
www.digi.com/howtobuy/terms
Customer support
Gather support information: Before contacting Digi technical support for help, gather the following
information:
Product name and model
Product serial number (s)
Firmware version
Operating system/browser (if applicable)
Logs (from time of reported issue)
XBee 868LP RF Modules User Guide
2
Trace (if possible)
Description of issue
Steps to reproduce
Contact Digi technical support: Digi offers multiple technical support plans and service packages.
Contact us at +1 952.912.3444 or visit us at www.digi.com/support.
Feedback
To provide feedback on this document, email your comments to
Include the document title and part number (XBee 868LP RF Modules User Guide, 90002126 S) in the
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XBee 868LP RF Modules User Guide
3
Contents
XBee 868LP RF Modules User Guide
XBee S8 hardware description 12
European acceptance 12
Technical specifications
Performance specifications 14
LBT and AFA specifications 14
Power requirements 15
General specifications 15
Networking and security 16
Regulatory conformity summary 16
Serial communication specifications 16
UART pin assignments 16
SPI pin assignments 17
GPIO specifications 17
Hardware specifications for the programmable variant 17
Hardware
Mechanical drawings 20
Pin signals 20
Design notes 22
Power supply design 22
Board layout 23
Antenna performance 23
Recommended pin connections 23
Design notes for PCB antenna devices 24
Design notes for RF pad devices 25
Module operation for the programmable variant 28
Programmable XBee SDK 29
Get started
Set up the devices 31
Before you begin 31
Connect the hardware 32
Step 1: Download and install XCTU 33
Step 2: Set up your first wireless connection 35
XBee 868LP RF Modules User Guide
4
Step 3: Create a mesh network 39
Step 4: Use API mode to talk to XBee modules 43
Do more with your XBee modules 47
Update the firmware 47
Configure remote devices 48
Set up and perform a range test 49
Configure basic synchronous sleep support 52
Set up basic encryption for an XBee network 57
Learn more about XBee module features 58
Unicast versus broadcast transmissions 58
Analog inputs and digital inputs and outputs 58
Sleep modes 59
Transparent and API operating modes 59
Troubleshooting 59
Cannot install device driver 59
Use LEDs to identify XBee modules 60
No remote devices to select for a range test 60
Port in use 61
XCTU cannot discover devices 61
XCTUcannot discover remote devices 62
XCTUcannot discover remote devices for a range test 62
XCTU installation error 63
Configure the XBee 868LP RF Module
Software libraries 66
XBee Network Assistant 66
Operation
Operation 68
Listen Before Talk and Automatic Frequency Agility 68
Single frequency mode band mode 69
Serial communications 69
UART data flow 69
SPI communications 70
SPI operation 71
Configuration considerations 73
Serial port selection 73
Data format 73
SPI parameters 74
Serial buffers 74
Serial receive buffer 74
Serial transmit buffer 74
UART flow control 74
CTS flow control 75
RTS flow control 75
Force UART operation 75
Condition 75
Solution 75
Serial interface protocols 75
Transparent operating mode 76
API operating mode 76
Comparing Transparent and API modes 76
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Modes
Transmit mode 79
Receive mode 79
Command mode 79
Enter Command mode 80
Troubleshooting 80
Send AT commands 80
Response to AT commands 81
Apply command changes 81
Make command changes permanent 81
Exit Command mode 81
Sleep mode 82
Sleep modes
About sleep modes 84
Asynchronous modes 84
Synchronous modes 84
Normal mode 84
Asynchronous pin sleep mode 84
Asynchronous cyclic sleep mode 85
Asynchronous cyclic sleep with pin wake up mode 85
Synchronous sleep support mode 85
Synchronous cyclic sleep mode 85
Wake timer 86
Indirect messaging and polling 86
Indirect messaging 86
Polling 86
Sleeping routers 87
Sleep coordinator sleep modes in the DigiMesh network 87
Synchronization messages 87
Become a sleep coordinator 90
Select sleep parameters 92
Start a sleeping synchronous network 92
Add a new node to an existing network 93
Change sleep parameters 94
Rejoin nodes that lose sync 94
Diagnostics 95
Advanced application features
Remote configuration commands 98
Send a remote command 98
Apply changes on remote devices 98
Remote command responses 98
Network commissioning and diagnostics 98
Configure devices 98
Network link establishment and maintenance 99
Place devices 100
Device discovery 101
Link reliability 101
Commissioning pushbutton and associate LED 104
I/O line monitoring 107
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I/O samples 107
Queried sampling 107
Periodic I/O sampling 109
Detect digital I/O changes 110
General Purpose Flash Memory 110
Access General Purpose Flash Memory 110
Work with flash memory 111
General Purpose Flash Memory commands 112
PLATFORM_INFO_REQUEST (0x00) 112
PLATFORM_INFO (0x80) 112
ERASE (0x01) 113
ERASE_RESPONSE (0x81) 113
WRITE (0x02) and ERASE_THEN_WRITE (0x03) 114
WRITE _RESPONSE (0x82) and ERASE_THEN_WRITE_RESPONSE (0x83) 114
READ (0x04) 115
READ_RESPONSE (0x84) 115
FIRMWARE_VERIFY (0x05) and FIRMWARE_VERIFY_AND_INSTALL(0x06) 116
FIRMWARE_VERIFY_RESPONSE (0x85) 117
FIRMWARE_VERIFY _AND_INSTALL_RESPONSE (0x86) 117
Over-the-air firmware updates 118
Distribute the new application 118
Verify the new application 119
Install the application 119
Networking methods
Directed Broadcast/Repeater mode 121
Point to Point/Multipoint mode 121
Permanent (dedicated) 121
Switched 121
DigiMesh networking 121
DigiMesh feature set 122
Networking concepts 123
Device Configuration 123
Network ID 123
Data transmission and routing 123
Unicast addressing 123
Broadcast addressing 123
Routing 124
Route discovery 124
DigiMesh throughput 124
Transmission timeouts 125
AT commands
Special commands 128
AC (Apply Changes) 128
FR (Software Reset) 128
RE (Restore Defaults) 128
WR (Write 128
MAC/PHY commands 129
CM (Channel Mask) 129
HP (Preamble ID) 129
ID (Network ID) 129
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MT(Broadcast Multi-Transmits) 130
PL (TX Power Level) 130
RR (Unicast Mac Retries) 130
ED (Energy Detect) 131
Diagnostic commands 131
BC (Bytes Transmitted) 131
DB (Last Packet RSSI) 131
ER (Received Error Count) 132
GD (Good Packets Received) 132
EA (MAC ACK Timeouts) 132
TR (Transmission Errors) 132
UA (MAC Unicast Transmission Count) 133
%H (MAC Unicast One Hop Time) 133
%8 (MAC Broadcast One Hop Time) 133
Network commands 133
CE (Node Messaging Options) 133
BH (Broadcast Hops) 134
NH (Network Hops) 134
NN (Network Delay Slots) 134
MR (Mesh Unicast Retries) 135
Addressing commands 135
SH (Serial Number High) 135
SL (Serial Number Low) 135
DH (Destination Address High) 136
DL (Destination Address Low) 136
TO (Transmit Options) 136
NI (Node Identifier) 137
NT (Node Discover Timeout) 137
NO (Node Discovery Options) 137
CI (Cluster ID) 138
DE (Destination Endpoint) 138
SE (Source Endpoint) 138
Addressing discovery/configuration commands 139
AG (Aggregator Support) 139
DN (Discover Node) 139
ND (Network Discover) 139
FN (Find Neighbors) 140
Diagnostic - addressing commands 141
N? (Network Discovery Timeout) 141
Security commands 141
EE (Security Enable) 141
KY (AES Encryption Key) 141
Serial interfacing commands 142
BD (Baud Rate) 142
NB (Parity) 142
SB (Stop Bits) 143
RO (Packetization Timeout) 143
FT (Flow Control Threshold) 143
AP (API Mode) 144
AO (API Options) 144
I/O settings commands 144
CB (Commissioning Pushbutton) 145
D0 (AD0/DIO0 Configuration) 145
D1 (DIO1/AD1) 145
D2 (DIO2/AD2) 146
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D3 (DIO3/AD3) 146
D4 (DIO4/AD4) 147
D5 (DIO5/ASSOCIATED_INDICATOR) 147
D6 (DIO6/RTS) 147
D7 (DIO7/CTS) 148
D8 (DIO8/SLEEP_REQUEST) 148
D9 (DIO9/ON_SLEEP) 149
P0 (DIO10/RSSI/PWM0 Configuration) 149
P1 (DIO11/PWM1 Configuration) 150
P2 (DIO12 Configuration) 150
P3 (DIO13/DOUT) 150
P4 (DIO14/DIN) 151
P5 (SPI_MISO) 151
P6 (SPI_MOSI Configuration) 151
P7 (DIO17/SPI_SSEL ) 152
P8 (DIO18/SPI_SCLK) 152
P9 (SPI_ATTN) 153
PD (Pull Up/Down Direction) 153
PR (Pull-up/Down Resistor Enable) 153
M0 (PWM0 Duty Cycle) 154
M1 (PWM1 Duty Cycle) 154
LT (Associate LED Blink Time) 155
RP (RSSI PWM Timer) 155
I/O sampling commands 155
AV (Analog Voltage Reference) 155
IC (DIO Change Detection) 156
IF (Sleep Sample Rate) 157
IR (I/O Sample Rate) 157
TP (Temperature) 157
IS (Force Sample) 157
%V (Voltage Supply Monitoring) 158
Sleep commands 158
SM (Sleep Mode) 158
SO (Sleep Options) 158
SN (Number of Cylcles Between ON_SLEEP) 159
SP (Sleep Period) 159
ST (Wake Time) 160
WH (Wake Host) 160
Diagnostic - sleep status/timing commands 160
SS (Sleep Status) 160
OS (Operating Sleep Time) 161
OW (Operating Wake Time) 161
MS (Missed Sync Messages) 161
SQ (Missed Sleep Sync Count) 162
Command mode options 162
CC (Command Sequence Character) 162
CT (Command Mode Timeout) 162
CN (Exit Command Mode) 162
GT (Guard Times) 163
Firmware commands 163
VL (Version Long) 163
VR (Firmware Version) 163
HV (Hardware Version) 163
HS (Hardware Series) 164
DD (Device Type Identifier) 164
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NP (Maximum Packet Payload Bytes) 164
CK (Configuration CRC) 164
Operate in API mode
API mode overview 166
API frame format 166
Data bytes that need to be escaped: 167
Calculate and verify checksums 168
API frame exchanges 169
Code to support future API frames 170
Frame data 171
Local AT Command Request - 0x08 172
Queue Local AT Command Request - 0x09 174
Transmit Request - 0x10 176
Explicit Addressing Command Request - 0x11 178
Remote AT Command Request - 0x17 181
Local AT Command Response - 0x88 184
Modem Status - 0x8A 186
Modem status codes 187
Extended Transmit Status - 0x8B 189
Route Information - 0x8D 191
Aggregate Addressing Update- 0x8E 193
Receive Packet - 0x90 195
Explicit Receive Indicator - 0x91 197
I/O Sample Indicator- 0x92 199
Node Identification Indicator - 0x95 202
Remote AT Command Response- 0x97 205
Migrate from XBee through-hole to surface-mount devices
Pin mapping 209
Mounting 210
Manufacturing information
Recommended solder reflow cycle 213
Recommended footprint and keepout 213
Flux and cleaning 215
Reworking 215
Regulatory information
Europe 218
Maximum power and frequency specifications 218
OEM labeling requirements 219
Declarations of conformity 220
Antennas 220
XBee 868LP RF Modules User Guide
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XBee 868LP RF Modules User Guide
The Digi XBee 868LP RF Modules provide wireless connectivity to end-point devices in mesh networks.
With the XBee, users can have their network up-and-running in a matter of minutes without
configuration or additional development. The Digi XBee 868LP RF Module consists of firmware loaded
onto Digi XBee S8 hardware.
You can build networks up to 128 nodes using the XBee modules. For larger networks up to 1000+
nodes, Digi offers RF Optimization Services to assist with proper network configuration. Contact Digi
Technical Support for more details.
Note The Digi XBee 868LP RF Modules are not compatible with other XBee products.
XBee S8 hardware description 12
European acceptance 12
XBee 868LP RF Modules User Guide
11
XBee 868LP RF Modules User Guide XBee S8 hardware description
XBee S8 hardware description
The XBee S8 radio module hardware consists of an Energy Micro EFM®32G230F128 microcontroller, an
Analog Devices ADF7023 radio transceiver, and in the Programmable version, a NXP MC9S08QE32
microcontroller.
European acceptance
The Digi XBee 868LP is manufactured under ISO 900:2015 registered standards.
The Digi XBee 868LP RF Modules are optimized for use in Europe and other regions. For more
information, see Regulatory information.
XBee 868LP RF Modules User Guide
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Technical specifications
Performance specifications 14
LBT and AFA specifications 14
Power requirements 15
General specifications 15
Networking and security 16
Regulatory conformity summary 16
Serial communication specifications 16
GPIO specifications 17
Hardware specifications for the programmable variant 17
XBee 868LP RF Modules User Guide
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Technical specifications Performance specifications
Performance specifications
The following table describes the performance specifications for the devices.
Note Range figure estimates are based on free-air terrain with limited sources of interference. Actual
range will vary based on transmitting power, orientation of transmitter and receiver, height of
transmitting antenna, height of receiving antenna, weather conditions, interference sources in the
area, and terrain between receiver and transmitter, including indoor and outdoor structures such as
walls, trees, buildings, hills, and mountains.
Specification
Indoor/urban range
Outdoor RF line-ofsight range
Transmit power
output
RF data rate (high)
RF data rate (low)
UART interface Complementary metal–oxide–semiconductor (CMOS) serial universal
UART data rate
(software
selectable)
SPI clock rate Up to 3.5 MHz
Receiver category Class 2
Receiver sensitivity
(typical)
XBee
Up to 370 ft (112 m) with a 2.1 dBi antenna, up to 46 ft (14 m) with a PCB
embedded antenna.
Up to 5.2 miles (8.4 km) with a 2.1 dBi antenna, up to 0.4 miles (.64 km) with
a PCB embedded antenna.
Up to 14 dBm (25 mW) EIRP with 2.1 dBi antenna
80 kb/s
10 kb/s
asynchronous receiver/transmitter (UART), baud rate stability of <1%.
9600-230400 baud
-101 dBm @ 80 kb/s, -106 dBm @ 10 kb/s.
Receiver blocking
(typical)
Note To determine your indoor/urban range or outdoor RF line-of-sight range, perform a range test
under your operating conditions.
Frequency offset Data rate
+/- 400 kHz 40 dB 35 dB
+/- 200 kHz 35 dB 29 dB
LBT and AFA specifications
The following table provides the Listen Before Talk (LBT) and Adaptive Frequency Agility (AFA)
specifications.
XBee 868LP RF Modules User Guide
10 kb/s 80 kb/s
14
Technical specifications Power requirements
Specification
Channel spacing 100 kHz
Receiver bandwidth 150 kHz
Modulation bandwidth < 300 kHz
LBT threshold < -88 dBm
TX on time < 1 second
Power requirements
The following table describes the power requirements for the XBee 868LP RF Module.
Specification
Supply voltage (VDD) 2.7 to 3.6 VDC
Transmit current, high data rate 48 mA, (45 mA typical)
Transmit current, low data rate 47 mA (41 mA typical)
Idle / receive current (high data rate) 27 mA (22 mA typical)
Idle / receive current (low data rate) 26 mA (24 mA typical)
XBee 868LP
XBee
Sleep current 1.7 µA
General specifications
The following table describes the general specifications for the devices.
Specification XBee
Operating frequency
band
Dimensions 2.119 x 3.4 x 0.305 cm (0.866 x 1.333 x 1.2 in)
Weight 40 g (1.4 oz)
Operatingtemperature -40 ºC to 85 ºC (industrial)
Antenna options
Digital I/O 13 I/O lines, five dedicated to Serial Peripheral Interface (SPI) that can be
ADC 4 10-bit analog inputs
863 to 870 MHz for Europe
U.FL RF connector, RF pad, embedded PCB antenna.
Note The embedded PCB antenna is only approved with 10 kb/s data rate,
not 80 kb/s data rate.
used as digital outputs.
XBee 868LP RF Modules User Guide
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Technical specifications Networking and security
Networking and security
The following table describes the networking and security specifications for the devices.
Specification
Supported network topologies Mesh, repeater, point-to-point, point-to-multipoint, peer-
Number of channels, user selectable
channels
Addressing options Personal Area Network identifier (PAN ID) and 64-bit
Encryption 128 bit Advanced Encryption Standard (AES)
Note For more information about the number of user selectable channels, see OEM labeling
requirements for countries in the European Community.
XBee
to-peer.
30 channels, LBT + AFA
addresses.
Regulatory conformity summary
This table describes the agency approvals for the devices.
Specification XBee
Europe (CE) Yes
Serial communication specifications
The XBee 868LP RF Module supports both Universal Asynchronous Receiver / Transmitter (UART) and
Serial Peripheral Interface (SPI)serial connections.
UART pin assignments
UART Pins Device Pin Number
DOUT 3
DIN / CONFIG
CTS / DIO7
RTS / DIO6
For more information on UART operation, see UART data flow.
4
25
29
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Technical specifications GPIO specifications
SPI pin assignments
SPI Pins Module Pin Number
SPI_SCLK / DIO18 (input) 14
SPI_SSEL / DIO17 (input)
SPI_MOSI / DIO16 (input) 16
SPI_MISO / DIO15 (output/tri-stated) 17
SPI_ATTN (output)
For more information on SPI operation, see SPI communications.
GPIO specifications
The XBee 868LP RF Modules have General Purpose Input / Output (GPIO) ports available. The exact
list depends on the module configuration, as some GPIO pads are used for purposes such as serial
communication.
You can set the pin configuration by using D0-D9, P0-P9, and I/O line monitoring. You cannot sample
pins P5-P9, but you may use them as outputs. For more information on these commands, see AT
commands. For more information on configuring and using GPIO ports, see Pin signals.
The following table provides the electrical specifications for the GPIO pads.
GPIO electrical specification Value
Low Schmitt switching threshold
High Schmitt switching threshold
15
12
0.3 x V
0.7 x V
DD
DD
Input pull-up resistor value 40 kΩ
Input pull-down resistor value 40 kΩ
Output voltage for logic 0
Output voltage for logic 1
Output source current 6 mA
Output sink current 6 mA
Total output current (for GPIO pads) 48 mA
0.05 x V
0.95 x V
Hardware specifications for the programmable variant
If the module includes the programmable secondary processor, add the following table values to the
specifications listed in Pin signals, Serial communication specifications, and GPIO specifications. For
example, if the secondary processor is running at 20 MHz and the primary processor is in receive
mode, then the new current value will be Itotal = Ir2 + Irx = 14 mA + 9 mA = 23 mA, where Ir2 is the
runtime current of the secondary processor and Irx is the receive current of the primary.
The following table provides the specifications of the programmable secondary processor.
DD
DD
XBee 868LP RF Modules User Guide
17
Technical specifications Hardware specifications for the programmable variant
Optional secondary processor
specification
Runtime current for 32 k running
at 20 MHz
Runtime current for 32 k running
at 1 MHz
Sleep current
V
Range
REF
Microcontroller
Add to RX, TX, and sleep currents specifications depending
on mode of operation
+14 mA
+1 mA
+0.5 µA typical
1.8 VDC to V
DD
NXP Flexis 8-bit S08 microcontroller NXP S08QE Family
Part number: MC9S08QE32
XBee 868LP RF Modules User Guide
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Hardware
Mechanical drawings 20
Pin signals 20
Design notes 22
Module operation for the programmable variant 28
Programmable XBee SDK 29
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Hardware Mechanical drawings
Mechanical drawings
The following mechanical drawings of the XBee 868LP RF Modules show all dimensions in inches.
Antenna options are not shown.
Pin signals
The following table describes the pin assignments for the devices. A horizontal line above the signal
name indicates low-asserted signals.
Pin# Name Direction
1 GND - - Ground
2 V
3 DIO13 / DOUT Both Output GPIO/UART Data Out
4 DIO14 / DIN / CONFIG Both Input GPIO/UART Data In
5 DIO12 Both GPIO
6 RESET Input Module reset. Drive low to
DD
Default
state Description
- - Power supply
reset the module. This is also
an output with an open drain
configuration with an internal
20 kW pull-up (never drive to
logic high, as the module may
be driving it low). The minimum
pulse width is 1 mS.
XBee 868LP RF Modules User Guide
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Hardware Pin signals
Default
Pin# Name Direction
7 DIO10 / RSSI PWM0 Both Output GPIO/RX Signal Strength
8 DIO11 / PWM1 Both Disabled GPIO/Pulse Width Modulator
9 [reserved] - Disabled Do not connect
10 DIO8 / SLEEP_REQUEST Both Input GPIO/Pin Sleep Control Line
11 GND - - Ground
12 DIO19 / SPI_ATTN Output Output
13 GND - - Ground
14 DIO18 / SPI_CLK Input Input GPIO/Serial Peripheral
state Description
Indicator
(DTR on the dev board)
Serial Peripheral Interface
Attention or UART Data
Present indicator
Interface Clock/
15 DIO17 / SPI_SSEL/ Input Input GPIO/Serial Peripheral
Interface not Select
16 DIO16 / SPI_MOSI Input Input GPIO/Serial Peripheral
Interface Data In
17 DIO15 / SPI_MISO/ Output Output GPIO/Serial Peripheral
Interface Data Out
Tri-stated when SPI_SSEL is
high
18 [reserved]* - Disabled Do not connect
19 [reserved]* - Disabled
20 [reserved]* - Disabled
21 [reserved]* - Disabled
22 GND - - Ground
23 [reserved] - Disabled Do not connect
24 DIO4 Both Disabled GPIO
25 DIO7 / CTS/ Both Output GPIO/Clear to Send Flow
Do not connect
Do not connect
Do not connect
Control
26 ON/SLEEP/DIO9 Both Output GPIO/Module Status Indicator
XBee 868LP RF Modules User Guide
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Hardware Design notes
Default
Pin# Name Direction
27 VREF Input -
28 DIO5 / ASSOCIATE/ Both Output GPIO/Associate Indicator
29 DIO6 / RTS Both Input GPIO/Request to Send Flow
30 DIO3 / AD3 Both Disabled GPIO/Analog Input
state Description
Not used internally. Used for
programmable secondary
processor. For compatibility
with other XBee modules, we
recommend connecting this
pin to the voltage reference if
Analog Sampling is desired.
Otherwise, connect to GND.
Control
31 DIO2 / AD2 Both Disabled
32 DIO1 / AD1 Both Disabled
33 DIO0 / AD0 Both Input GPIO/Analog Input
34 [reserved] - Disabled Do not connect
35 GND - - Ground
36 RF Both - RF I/O for RF Pad Variant
37 [reserved] - Disabled Do not connect
Signal Direction is specified with respect to the device.
See Design notes for details on pin connections.
* These pins are not available for customer use.
Design notes
The XBee modules do not require any external circuitry or specific connections for proper operation.
However, there are some general design guidelines that we recommend to build and troubleshoot a
robust design.
GPIO/Analog Input
GPIO/Analog Input
Power supply design
A poor power supply can lead to poor radio performance, especially if you do not keep the supply
voltage within tolerance or if the noise is excessive. To help reduce noise, place a 1.0 µF and 47 pF
capacitor as near as possible to pin 2 on the PCB. If you are using a switching regulator for the power
supply, switch the frequencies above 500 kHz. Limit the power supply ripple to a maximum 250 mV
peak to peak.
For designs using the programmable modules, we recommend an additional 10 µF decoupling cap
near pin 2 of the device. The nearest proximity to pin 2 of the three caps should be in the following
order:
XBee 868LP RF Modules User Guide
22
Hardware Design notes
1. 47 pf
2. 1 µF
3. 10 µF
Board layout
We design XBee modules to be self-sufficient and have minimal sensitivity to nearby processors,
crystals or other printed circuit board (PCB) components. Keep power and ground traces thicker than
signal traces and make sure that they are able to comfortably support the maximum current
specifications. There are no other special PCB design considerations to integrate XBee modules, with
the exception of antennas.
To view a recommended PCB footprint for the module, see Manufacturing information.
Antenna performance
Antenna location is important for optimal performance. The following suggestions help you achieve
optimal antenna performance. Point the antenna up vertically (upright). Antennas radiate and receive
the best signal perpendicular to the direction they point, so a vertical antenna's omnidirectional
radiation pattern is strongest across the horizon.
Position the antennas away from metal objects whenever possible. Metal objects between the
transmitter and receiver can block the radiation path or reduce the transmission distance. Objects
that are often overlooked include:
n Metal poles
n Metal studs
n Structure beams
n Concrete, which is usually reinforced with metal rods
If you place the device inside a metal enclosure, use an external antenna. Common objects that have
metal enclosures include:
n Vehicles
n Elevators
n Ventilation ducts
n Refrigerators
n Microwave ovens
n Batteries
n Tall electrolytic capacitors
Use the following additional guidelines for optimal antenna performance:
n Do not place XBee modules with the chip antenna inside a metal enclosure.
n Do not place any ground planes or metal objects above or below the antenna.
n For the best results, mount the device at the edge of the host PCB. Ensure that the ground,
power, and signal planes are vacant immediately below the antenna section.
Recommended pin connections
The only required pin connections for two-way communication are VDD, GND, DOUT and DIN. To
support serial firmware updates, you must connect VDD, GND, DOUT, DIN, RTS, and DTR.
XBee 868LP RF Modules User Guide
23
Hardware Design notes
Do not connect any pins that are not in use. Use the PR and PD commands to pull all inputs on the
radio high or low with 40k internal pull-up or pull-down resistors. Unused outputs do not require any
specific treatment.
For applications that need to ensure the lowest sleep current, never leave unconnected inputs
floating. Use internal or external pull-up or pull-down resistors, or set the unused I/O lines to outputs.
You can connect other pins to external circuitry for convenience of operation including the Associate
LED pad (pad 28) and the Commissioning pad (pad 33). The Associate LED pad flashes differently
depending on the state of the module to the network, and a pushbutton attached to pad 33 can
enable various join functions without having to send serial port commands. For more information see
Commissioning pushbutton and associate LED. The source and sink capabilities are limited to 6 mA on
all I/O pads.
Only the programmable versions of these devices use the VREF pad (pad 27). For compatibility with
other XBee modules, we recommend connecting this pin to a voltage reference if you want to enable
analog sampling. Otherwise, connect to GND.
Design notes for PCB antenna devices
Position PCB antenna devices so there are no ground planes or metal objects above or below the
antenna. For best results, do not place the device in a metal enclosure, as this may greatly reduce the
range. Place the device at the edge of the PCB on which it is mounted. Make sure the ground, power
and signal planes are vacant immediately below the antenna section.
The following drawings illustrate important recommendations when you are designing with PCB
antenna devices. For optimal performance, do not mount the device on the RF pad footprint described
in the next section, because the footprint requires a ground plane within the PCB antenna keep out
area.
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Hardware Design notes
Notes
1. We recommend non-metal enclosures. For metal enclosures, use an external antenna.
2. Keep metal chassis or mounting structures in the keepout area at least 2.54 cm (1 in) from the
antenna.
3. Maximize the distance between the antenna and metal objects that might be mounted in the
keepout area.
4. These keepout area guidelines do not apply for wire whip antennas or external RFconnectors.
Wire whip antennas radiate best over the center of a ground plane.
Design notes for RF pad devices
The RF pad is a soldered antenna connection. The RF signal travels from pin 33 on the device to the
antenna through an RF trace transmission line on the PCB. Any additional components between the
device and antenna violates modular certification. The controlled impedance for the RF trace is 50 Ω.
We recommend using a microstrip trace, although you can also use a coplanar waveguide if you need
more isolation. A microstrip generally requires less area on the PCB than a coplanar waveguide. We do
not recommend using a stripline because sending the signal to different PCB layers can introduce
matching and performance problems.
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Hardware Design notes
Following good design practices is essential when implementing the RF trace on a PCB. Consider the
following points:
n Minimize the length of the trace by placing the RPSMA jack close to the device.
n Connect all of the grounds on the jack and the device to the ground planes directly or through
closely placed vias.
n Space any ground fill on the top layer at least twice the distance d (in this case, at least 0.028")
from the microstrip to minimize their interaction.
Additional considerations:
n The top two layers of the PCB have a controlled thickness dielectric material in between.
n The second layer has a ground plane which runs underneath the entire RF pad area. This
ground plane is a distance d, the thickness of the dielectric, below the top layer.
n The top layer has an RF trace running from pin 33 of the device to the RF pin of the RPSMA
connector.
n The RF trace width determines the impedance of the transmission line with relation to the
ground plane. Many online tools can estimate this value, although you should consult the PCB
manufacturer for the exact width.
Implementing these design suggestions helps ensure that the RF pad device performs to its
specifications.
The following figures show a layout example of a host PCB that connects an RF pad device to a right
angle, through-hole RPSMA jack.
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Hardware Design notes
Number Description
1
2 Device pin 33.
2 RF pad pin.
3 50 Ω microstrip trace.
4 RF connection of RPSMA jack.
The width in this example is approximately 0.025 in for a 50 Ω trace, assuming d = 0.014 in, and that
the dielectric has a relative permittivity of 4.4. This trace width is a good fit with the device footprint's
0.335" pad width.
Note We do not recommend using a trace wider than the pad width, and using a very narrow trace
(under 0.010") can cause unwanted RF loss.
The following illustration shows PCB layer 2 of an example RF layout.
Maintain a distance of at least 2 d between microstrip and ground fill.
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Hardware Module operation for the programmable variant
Number Description
1
2 Put a solid ground plane under RF trace to achieve the desired impedance.
Use multiple vias to help eliminate ground variations.
Module operation for the programmable variant
The modules with the programmable option have a secondary processor with 32k of flash and 2k of
RAM. This allows module integrators to put custom code on the XBee module to fit their own unique
needs. The DIN, DOUT, RTS, CTS, and RESET lines are intercepted by the secondary processor to allow
it to be in control of the data transmitted and received. All other lines are in parallel and can be
controlled by either the internal microcontroller or the MC9SO8QE micro; see the block diagram in
Operation for details. The internal microcontroller by default has control of certain lines. The internal
microcontroller can release these lines by sending the proper command(s) to disable the desired DIO
line(s). For more information about commands, see AT commands.
For the secondary processor to sample with ADCs, the XBee must be connected to a reference
voltage.
Digi provides a bootloader that can take care of programming the processor over-the-air or through
the serial interface. This means that over-the-air updates can be supported through an XMODEM
protocol. The processor can also be programmed and debugged through a one wire interface BKGD .
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Hardware Programmable XBee SDK
Programmable XBee SDK
The XBee Programmable module is equipped with a NXP MC9S08QE32 application processor. This
application processor comes with a supplied bootloader. To interface your application code running on
this processor to the XBee Programmable module's supplied bootloader, use the Programmable XBee
SDK.
To use the SDK, you must also download CodeWarrior. The download links are:
n CodeWarrior IDE: http://ftp1.digi.com/support/sampleapplications/40003004_B.exe
n Programmable XBee SDK: http://ftp1.digi.com/support/sampleapplications/40003003_D.exe
If these revisions change, search for the part number on Digi’s website. For example, search for
40003003.
Install the IDE first, and then install the SDK.
The documentation for the Programmable XBee SDK is built into the SDK, so the Getting Started guide
appears when you open CodeWarrior.
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Get started
The XBee 868LP RF Modules support low-power, peer-to-peer or wireless mesh networks for Europe
(868 MHz). The XBee 868LP RF Modules provide reliable delivery of data between remote devices.
This guide shows you how to set up a mesh network using the DigiMesh protocol, send data between
devices, and adjust XBee 868LP RF Module settings.
Note For more information about DigiMesh protocol and features, see DigiMesh networking.
This guide covers the following tasks and features:
Set up the devices 31
Do more with your XBee modules 47
Learn more about XBee module features 58
Troubleshooting 59
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