More on Xbee part one.

Xbee is the device that integrate Microcontroller and RF IC into one piece (one module).
It work as transceiver equipment (the equipment that can both send and receive signal).
Xbee is half-duplex and it operate at 2.4 GHz frequency band. It consume low electric power and easy to use because
the interface used for sending and receiving data with Xbee is UART (TTL), so we can connect the UART communication pin of Xbee to
the UART of microcontroller directly.

Common features summary of Xbee
1. Operating Frequency ISM Band 2.4 GHz
(ISM Band is the frequency band that reserved for use in scientific , medical and industrial purpose. To know more
about ISM Band , please visit this wikipedia page)
2. Supply Voltage between 2.8 – 3.4 Volt
3. Can use together with various types of antenna such as Chip Antenna , Whip Antenna and connector like
U.FL connector , RP-SMA connector (but you have to find the 2.4 GHz antenna in order to use with these connectors).
4. Power Down Current < 10 uA 5. RF data rate of Xbee is about 250 Kbps (this is the data rate of signal that sent via the air) 6. Serial interface data rate is between 1200 - 115200 Bps (this is the data rate of communication between Xbee module and microcontroller)

Xbee Pin

Xbee has 20 pin (you can see pin-arrangement in the above picture).The function of each pin is described in page 7 of this datasheet.
Xbee also has Digital I/O line and 10 bits Analog to Digital converter module.

The distance between adjacent pin of Xbee is 2.0 mm so it cannot attach to the protoboard directly because
in general , standard distance between each pin of IC (Pitch) is 2.54 mm or 1 mil. However there’re many
tools used for convert the 2mm-10pin of Xbee into standard pitch (2.54mm) such as “2mm 10pin XBee Socket” or
“Breakout Board for XBee Module”.You should try to search for them at Sparkfun.com.

Kind of antenna that able to connect to Xbee module (I explain only four antenna kinds).

Xbee chip antenna

Chip antenna.

This kind of antenna is suitable for use in small project that restrict in size or dimension because its antenna is small single chip.
You can pack it in the box but only plastic box (don’t enclose it with steel box because the signal cannot spread through the steel).

Xbee wire antenna

Wire antenna.

With this kind of antenna, the range of the signal and stability is conformable with specification. However, the antenna that extrude from the Xbee module
may look untidy and you cannot pack it into the box too. If you want to use Xbee module in general task and don’t have limitaion in space or size of the workpiece
, I recommend this kind of antenna.

Xbee UFL antenna

UFL antenna.

This kind of antenna is suitable for the task that designed to place the Xbee module inside the box but allow the antenna to emerge from the box. With UFL antenna ,
you need to connect the UFL to SMA wire from the Xbee module to antenna. At this point , it may reduce the signal strength , however , at the antenna,
the signal can be amplified again so you should consider the expansion radio (Gain) at the antenna too.

Xbee SMA antenna

SMA antenna.

With this kind of antenna , the range of the signal and stability is in line with Xbee specification and is the best when compare to other types.
The signal can be amplified again at the antenna too.
The only disadvantage of SMA antenna is “it’s so difficult to adapt this kind of antenna to use inside the box”.

The next article will be about “how to choose the Xbee module to befit your embedded project”.

Reference : www.thaieasyelec.com , www.thaieasyelec.net

Thank you,
Jitkasem

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