Operation Serial interface
XBee/XBee-PRO® S2C ZigBee® RF Module
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Serial interface
The XBee/XBee-PRO ZigBee RF Module interface to a host device through a serial port. The device can
communicate with any logic and voltage compatible UART, through a level translator to any serial
device (for example, through a RS-232 or USB interface board), or through a SPI, as described in SPI
communications.
Note Two Wire serial Interface (TWI) is also available, but not supported by Digi. For information on
the TWI, see the EM357 pin mappings.
UART data flow
Devices that have a UART interface connect directly to the pins of the XBee/XBee-PRO ZigBee RF
Module as shown in the following figure. The figure shows system data flow in a UART-interfaced
environment. Low-asserted signals have a horizontal line over the signal name.
Serial data
A device sends data to the XBee/XBee-PRO ZigBee RF Module's UART through TH pin 4/SMT pin 4
(DIN) as an asynchronous serial signal. When the device is not transmitting data, the signals should
idle high.
For serial communication to occur, you must configure the UART of both devices (the microcontroller
and the XBee/XBee-PRO ZigBee RF Module) with compatible settings for the baud rate, parity, start
bits, stop bits, and data bits.
Each data byte consists of a start bit (low), 8 data bits (least significant bit first) and a stop bit (high).
The following diagram illustrates the serial bit pattern of data passing through the device. The
diagram shows UART data packet 0x1F (decimal number 31) as transmitted through the device.
You can configure the UART baud rate, parity, and stop bits settings on the device with the BD, NB,
and SB commands respectively. For more information, see Serial interfacing commands.
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