Hardware
Design notes
XBee Wi-Fi RF Module User Guide
27
supply, switch the frequencies above 500 kHz. Limit the power supply ripple to a maximum 50 mV
peak to peak.
Pin connection recommendations
The only required pin connections are VCC, GND, and either DOUT and DIN or SPI_CLK, SPI_SSEL, SPI_
MOSI, and SPI MISO. To support serial firmware updates, you should connect VCC, GND, DOUT, DIN,
RTS, and DTR.
Leave all unused pins disconnected. Use the
PR
command to pull all of the inputs on the device high
using 40 k internal pull-up resistors. You do not need a specific treatment for unused outputs.
For applications that need to ensure the lowest sleep current, never leave inputs floating. Use internal
or external pull-up or pull-down resistors, or set the unused I/O lines to outputs. You can achieve the
deep sleep (pin sleep) current specification using a standard XBee Interface Board with the XBee Wi-Fi
RF Module's pull-up and pull-down resistors configured as default.
You can connect other pins to external circuitry for convenience of operation. For example, the
Associate signal (through-hole pin 15 / surface-mount pin 28) and the ON_SLEEP signal (through-hole
pin 13 / surface-mount pin 26) will change level or behavior based on the state of the device.
Board layout
When designing the host PCB, account for the device dimensions shown in
. See
for the recommended footprints and required keepout areas. Use good
design practices when connecting power and ground, making those traces wide enough to
comfortably support the maximum currents or using planes if possible.
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:
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metal poles
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metal studs
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structure beams
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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:
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vehicles
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elevators
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ventilation ducts
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refrigerators
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microwave ovens
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batteries
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tall electrolytic capacitors