User Manual

XBee® Wi-Fi RF Modules

Poor power supply can lead to poor radio performance, especially if the supply voltage

is not kept within tolerance or is excessively noisy. To help reduce noise, a 1µF and

8.2pF capacitor are recommended to be placed as near to pin 1 on the PCB as possible.

If using a switching regulator for your power supply, switching frequencies above 500

kHz are preferred. Power supply ripple should be limited to a maximum 50mV peak to

peak.

Recommended Pin Connections

The only required pin connections are VCC, GND, and either DOUT and DIN or SPI_CLK,

SPI_nSSEL, SPI_MOSI, and SPI MISO. To support serial firmware updates, VCC, GND,

DOUT, DIN, RTS, and DTR should be connected.

All unused pins should be left disconnected. All inputs on the radio can be pulled high

with 30k internal pull-up resistors using the PR software command. No specific

treatment is needed for unused outputs.

For applications that need to ensure the lowest sleep current, inputs should never be

left floating. Use internal or external pull-up or pull-down resistors, or set the unused

I/O lines to outputs.

Other pins may be connected to external circuitry for convenience of operation. For

example, the Associate signal (pin 15) and the On_nSLEEP signal (pin 13) will change

level or behavior based on the state of the module.

Board Layout

XBee modules do not have any specific sensitivity to nearby processors, crystals or other

PCB components. Other than mechanical considerations, no special PCB placement is

required for integrating XBee radios except for those with integral antennas. In general,

Power and GND traces should be thicker than signal traces and be able to comfortably

support the maximum currents.

The radios are also designed to be self sufficient and work with the integrated and

external antennas without the need for additional ground planes on the host PCB.

However, considerations should be taken on the choice of antenna and antenna

location. Metal objects that are near an antenna cause reflections and may reduce the

ability for an antenna to efficiently radiate. Using an integral antenna in an enclosed

metal box will greatly reduce the range of a radio. For this type of application an

external antenna would be a better choice.

External antennas should be positioned away from metal objects as much as possible.

Metal objects next to the antenna or between transmitting and receiving antennas can

often block or reduce the transmission distance. Some objects that are often overlooked

are metal poles, metal studs or beams in structures, concrete (it is usually reinforced

with metal rods), metal enclosures, vehicles, elevators, ventilation ducts, refrigerators

and microwave ovens.