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XBee Basics and AT Transparent Mode

On this tutorial I will show you the basics of XBee, why they are usefull for wireless control applications and the basic configuration for AT Mode.

Wireless Brief Explanation.

Wireless communications have rised over these years and nowadays the “Internet of Things” is growing extremely fast.  The necessity of email services, exchange of information and newer applications like multimedia streaming indicates that this will continue.

The first one amazing standard was 802.11 (we know it as Ethernet) and has a data rate of 2 Mbps; and there so on 802.11a,b,g,n.  In particular, 802.11n has data rates up to 600 Mbps.

Next one well known is the Bluetooth 1.0 standard (802.15.1) developed in the second semester of 1999.  Right now we have the v4.0 standard and goes over 24 Mbps.

Of course there are a lot of wired and wireless standards, but now we will focus on Zigbee standard.

Zigbee is a specification for a suite of high level communication protocols used to create PAN (Personal Area Networks) built from small, low power digital radios.  Zigbee is based on 802.15 standard and is oriented to create mesh networks.

The basic use of Zigbee are for applications that require low data rates up to 250 kbps like sensors or input devices.

 

What are XBees?

xbee

XBees are RF embedded modules that are ruled by the 802.15.4 standard (someones are true Zigbee compliant modules).  They are DSSS (Direct Sequence Spread Spectrum), a technology now open to people and in the early years only for military purposes because the low immunity of jamming (of course, this benefit comes with a limitation, it takes more bandwidth).

My own are 2.4 GHz XBP24-AWI 802.15.4, but there are 900 Mhz XBees.  These devices are 3.3V operation and must be powered on this range of voltage input.  You could get a range between 1500 meters with LOS (Line-Of-Sight).  I achivieved at outdoor, in the city, near 40 meters with a lot of wall barriers, so they are fine.  In a building of 10 meters I achieved total communication between the last floor and the base floor in vertical position.

Some features and benefits are:

  • 802.15.4 / Multidrop network topologies
  • 2.4 GHz for worldwide / 900 MHz for long-range deployment
  • Common footprint for any RF Module from Digi
  • Multiple antenna options (Wire, u.FL, RPSMA)
  • Industrial grade rating (-40°C to 85°C)

 

Which topologies are supported?

These devices are ideal for communication because handles all the basics configurations:

  • Point to Point
  • Peer To Peer (also called P2P)
  • Multipoint
  • Star
  • Mesh

There are some examples of basic networks types:

somebasicnetworks

Basically we can treat them as an intelligent replacement of anything that is being wired to be wireless because it has a very simple serial interface.

Which could be possibles smarts application using XBees?

xbeenetwork

Example of apllications include:

  • Industrial control and monitoring:  You could use it in sensors in a plant that monitors variables of your process and then transmit wirelessly to the main station.
  • Home automation and consumer electronics:  In your home a basic example is a centralized universal remote controller, maybe an wireless node of light sensors and so on.
  • Security and Military sensing:  In this area we could apply a system that can be capable of monitor radiation elements and send it to a database for dataloggind and post analyze.
  • Asset Tracking and Supply Chain Management:  Of course, an important application could be a fleet management system.  When the fleet arrives the base, it will send all sort of data logged on the system like fuel consumption of the day, car sensor data (faulty or not), and how many boxes of a product where delivered by the day.
  • Intelligent Agriculture and Enviromental Sensing:  A simple application could be tha sense of the farm animals and where they are.
  • Health Monitoring:  This could be a biological monitor of all human bodies variables that will announce your body limits or maybe a monitor for your glucose level and make your life more healthy.

 

XBee Series?

Now there are a lot of Xbees devices, I will only compare the basic Series 1.

This is a basic comparative table of XBees from its manual for the Series 1:

 

Platform

XBee® 802.15.4 (Series 1)

Platform XBee-PRO® 802.15.4 (Series 1)

XBee-PRO® XSC

Performance
RF Data Rate

250 kbps

250 kbps

10 kbps / 9.6 kbps

Indor/Urban Range

100 ft (30 m)

300 ft (100 m)

Up to 1200 ft (370 m)

Outdoor/RF Line-of-Sight Range

300 ft (100 m)

1 mi (1.6 km)

Up to 6 mi (9.6 km)

Transmit Power

1 mW (+0 dBm)

60 mW (+18 dBm)*

100 mW (+20 dBm)

Receiver Sensitivity (1% PER)

-92 dBm

-100 dBm

-106 dBm

Features
Serial Data Interface

3.3V CMOS UART

3.3V CMOS UART

3.3V CMOS UART (5V Tolerant)

Configuration Method

API or AT Commands, local or over-the-air

API or AT Commands, local or over-the-air

AT Commands

Frequency Band

2.4 GHz

2.4 GHz

902 MHz to 928 MHz

Interference Immunity

DSSS (Direct Sequence Spread Spectrum)

DSSS (Direct Sequence Spread Spectrum)

FHSS (Frequency Hopping Spread Spectrum)

Serial Data Rate

1200 bps – 250 kbps

1200 bps – 250 kbps

1200 bps – 57.6 kbps

ADC Inputs

(6) 10-bit ADC inputs

(6) 10-bit ADC inputs

None

Digital I/O

8

8

None

Antenna Options

Chip, Wire Whip, U.FL, & RPSMA

Chip, Wire Whip, U.FL, & RPSMA

Wire Whip, U.FL, RPSMA

Networking & Security
Encryption

128-bit AES

128-bit AES

No

Reliable Packet Delivery

Retries/Acknowledgments

Retries/Acknowledgments

Retries/Acknowledgements

IDs and Channels

PAN ID, 64-bit IEEE MAC, 16 Channels

PAN ID, 64-bit IEEE MAC, 12 Channels

PAN ID, 32-bit Address, 7 Channels

Power Requirements
Supply Voltage

2.8 – 3.4VDC

2.8 – 3.4VDC

3.0 – 3.6VDC

Transmit Current

45 mA @ 3.3VDC

215 mA @ 3.3VDC

265 mA typical

Receive Current

50 mA @ 3.3VDC

55 mA @ 3.3VDC

65 mA typical

Power-Down Current

<10 uA @ 25º C

<10 uA @ 25º C

45 uA pin Sleep

Regulatory Approvals
FCC (USA)

OUR-XBEE

OUR-XBEEPRO

MCQ-XBEEXSC

IC (Canada)

4214A-XBEE

4214A-XBEEPRO

1846A-XBEEXSC

ETSI (Europe)

Yes

Yes* Max TX 10 mW

No

C-TICK Australia

Yes

Yes

No

Telec (Japan)

Yes

Yes*

No

 

XBee Pinouts

One big difference between the XBee and XBee Pro are the output power.  XBee Pro’s are more powerfull for data transmission trought long distance, but XBee are better for low power rate.

On the other hand, XBee and XBee Pro’s are different in footprint and pinout, there is the table of all XBees footprint:

xbee1

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

5

RESET

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

9

DTR / 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

 

XBee Pro Networking Modes

The XBee/XBee-PRO RF modules supports this IEEE 802.15.4 network types:

  • NonBeacon
  • NonBeacon (w/ Coordinator)
  • When XBee’s are networked you could put it on three different modes, it must be clear wich devices is acting as:

Term Definition
PAN Personal Area Network – A data communication network that includes one or more End Devices and optionally a Coordinator.
Coordinator A Full-function device (FFD) that provides network synchronization by polling nodes [NonBeacon (w/ Coordinator) networks only]
End Device When in the same network as a Coordinator – RF modules that rely on a Coordinator for synchronization and can be put into states of sleep for low-power applications.
Association The establishment of membership between End Devices and a Coordinator. Association is only applicable in NonBeacon (w/Coordinator) networks.

 

xbeep2p

Nonbeacon P2P Network

Nonbeacon

Nonbeacon is the basic configuration of XBee and is peer-to-peer, it doesn’t depends of master/slave relationships.  On other words, they remain synchronized without use of master/server configurations and each module in the network shares both roles of master and slave.

Nonbeacon w/ Coordinator

In this networking mode the coordinator can be configured to use direct or indirect transmission.  One thing to note is that 802.15.4 always requires a coordinator, but this Digi RF Modules may have it or not.

xbeenesimplenetwork

Suppose that the PC wants to pass data to turn on the pump and there is a far distance that one device can’t handle direct communication.  The network must be capable to find the transmission path between the network, retransmission and acks are also handled.  If the last router ‘R’ is removed, the network must be capable to find other path to deliver the message.

XBee Initial Setup in AT Mode (Transparent Mode)

In transparent mode you can pass data as if you were using wires.

Here is a video of setting up X-CTU Software:

Here is another video showing you how to test basic settings in transparent mode AT command set using X-CTU:

Thanks for read the article, for more information and details you could check on Sparkfun and Wikipedia.

Permanent link to this article: http://cerescontrols.com/tutorials-3/xbee-basics-at/

2 comments

  1. santiago arroyave

    hi,

    when I configure my XBee module in transparent mode, can they work in full duplex transmission?

    thank you

    1. Rangel Alvarado

      I inspected the manual, assuming you are using the device that i listed here, and its only half-duplex.

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