Why do I need an adapter board for the XBee?

The XBee is a 20 pin device with 2mm spacing (breadboards are typically 2.54mm or 0.1 in).  Even if the pins did fit, it would gobble up most of the real estate on smaller breadboards.  The XBee is also a 3.3V device.  The adapter is regulated for 3.3V and has a 5V to 3.3V buffer.  Voltages from the XBee to the controller do not need to be conditioned since they are higher than the BASIC Stamp’s threshold voltage (1.8V).

What is IEEE 802.15.4 and ZigBee?

IEEE 802.15.4 is a low-rate communications protocol for wireless networks.  The protocol is responsible for moving data between 2 addressable devices, much like Ethernet moves data (IEEE 802.3).  This protocol uses the 900MHz or 2.4GHz (XBee) bands, and uses Direct Spread Spectrum Sequence to use very low power for transmission.

ZigBee is a trademark of a consortium of companies in developing compatible applications on top of 802.15.4.  ZigBee can be compared to TCP/IP, which uses 802.3 to move data.  ZigBee includes the ability to route data between points. 

Can I communicate with my WiFi network?

Not directly.  IEEE 802.15.4 operates on a different protocol (and purpose!) than WiFi (IEEE 802.11).

What is different about these devices from other RF devices, such as 433MHz ones?

Many RF devices simple send data freely without regard to errors or collisions with data from other devices.  IEEE 802.15.4 is a fully implemented protocol ensuring as much as possible that data between devices do not collide (media access control), and the packets arrive without errors.  Of course, addressing is a major benefit also.

Does the XBee support routing?

The version of the firmware discussed here, 1.083, is mainly 802.15.4.  Other versions are in beta, which may include ZigBee functions of routing, though they may not be compatible with the examples illustrated here.  With a little coding, routing may be designed into the BASIC Stamp to assist in these needs.

Can I use other I/O on the XBee that are not pinned out to the header?

Yes, for outputs you may simply run a jumper from the XBee header to your breadboard, keeping in mind it is 3.3V.  For inputs to the XBee, your signal must be conditioned using a voltage or other means to 3.3V.

Can I use this board with controllers other then the BASIC Stamp?

Yes, any controller or device, 5V logic or 3.3V logic may be used, such as the Propeller or SX series from Parallax.  The 3.3V regulator on the boards requires at least 5V to Vin.  If this is unavailable on your 3.3V board, you may customize your board and keep off and jumper the regulator holes pin 1 to 3.

How much current does the AppBee board draw?

With an XBee, current draw is around 50mA.  With an XBee-PRO, current draw can exceed 180mA when transmitting.  Sleep mode may be used to lower current draw to <2mA, but the unit cannot send nor receive while sleeping.  Lower power can be obtained by using a LT1521CST-3.3-ND surface mount voltage regulator instead of the T0-220 style provided.  The boards have pads for them, but they may have solder mask over the top that may need to be scraped off.

How can I reprogram the firmware on my XBee?

A serial connection providing DTR and other hardware handshaking lines is required.  The USB Base Station may be used to update the firmware on the XBee.

Is the unit RoHS compliant?

All parts and soldered used are rated as RoHS, though older stock of part (resistors, capacitors) from supplies may have been sent which was not compliant.  So… It should be compliant, but not guaranteed at this time.  Recent versions of the XBee itself are compliant and compliant solder is used in assembled boards. 

Why can’t I reach 1500 meters with the XBee-PRO or 300 meters with the XBee?

RF can be a tricky thing due to reflection, scattering and absorption.  Even out doors, line of sight means more than the units are in sight of each other.  Think of the signal between the 2 antennae as a football shaped field.  The further the antennae are apart, the wider this football will be.  If the field hits a surface, energy is reflected and will interfere with received data.  For example, at 100 meters, the antennae should be 1.5 meters high for optimal transmission.  At further distances, the higher the units need to be.  With the AppBee SIP, the antenna being bent upward is not the best configuration, but should provide adequate transmission paths.

Are there other antenna styles available?

Yes, XBee’s are available with a chip antenna and connectors for larger dipole antenna.  These are available from vendors listed in the next section, but we plan on keeping a small stock of Whip antennas only.




Website and software copyright 2009, SelmaWare Solutions
BASIC Stamp is a registered trademark of Parallax, Inc
XBee is a registered trademark of Digi International
Excel is a registered trademark of Microsoft, Corp.

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