Antenna Performance; Recommended Pin Connections - Digi XBee-PRO S2C Zigbee User Manual

Hardware

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:
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
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If you place the device inside a metal enclosure, use an external antenna. Common objects that have
metal enclosures include:
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
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Use the following additional guidelines for optimal antenna performance:
Do not place XBee modules with the chip or integrated PCB antenna inside a metal enclosure.
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Do not place any ground planes or metal objects above or below the antenna.
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For the best results, mount the device at the edge of the host PCB. Ensure that the ground,
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power, and signal planes are vacant immediately below the antenna section.
For more information, see
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Recommended pin connections

The only required pin connections for two-way communication are VCC, GND, DOUT and DIN. To
support serial firmware updates, you must connect VCC, GND, DOUT, DIN, RTS, and DTR.
Do not connect any pins that are not in use. Use the PR command to pull all inputs on the radio high
with internal pull-up 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 pin (pin 15) and the Commissioning pin (pin 20). The Associate LED pin flashes differently
depending on the state of the module, and a pushbutton attached to pin 20 can enable various
deployment and troubleshooting functions without you sending UART commands. For more
information, see Commissioning pushbutton and associate
For analog sampling, attach the VREF pin (pin 14) to a voltage reference.
XBee/XBee-PRO® S2C Zigbee® RF Module
Design notes for PCB antenna
LED.
Design notes
devices.
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