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XBee® Wi-Fi RF Modules

Serial Interface Protocols

The XBee modules support both transparent and API (Application Programming

Interface) serial interfaces.

Transparent Operation

When operating in transparent mode, the modules act as a serial line replacement. All

UART data received is queued up for RF transmission. When RF data is received, the

data is sent out through the UART. The module configuration parameters are configured

using the AT command mode interface. Please note that transparent operation is not

an option when using SPI.

Data is buffered in the serial receive buffer until one of the following causes the data to

be packetized and transmitted:

• No serial characters are received for the amount of time determined by the RO

parameter. If RO is zero, data is packetized as soon as it is received, without

delay. If RO is non-zero, the data is packetized after RO character times of no

transitions on the DIN pin. However, if the time required for RO characters is

less than 100 microseconds, then DIN must still be idle for at least 100

microseconds, which is the minimal idle time required for packetizing packets at

any baud rate.

• The Command Mode Sequence (GT + CC + GT) is received. Any character

buffered in the serial receive buffer before the sequence is packetized and

transmitted before command mode is entered.

• The maximum number of characters that will fit in an RF packet is received.

API Operation

API operation is an alternative to transparent operation. The frame-based API extends

the level to which a host application can interact with the networking capabilities of the

module. When in API mode, all data entering and leaving the UART or SPI is contained in

frames that define operations or events within the module.

Transmit Data Frames (received through the DIN or SPI_MOSI pin) include:

• RF Transmit Data Frame

• Local commands (equivalent to AT commands)

• Remote commands to be sent to another radio

Receive Data Frames (sent out the DOUT or SPI_MISO pin) include:

• RF-received data frames

• Local command responses

• Remote command responses

• I/O samples from a remote radio

• Event notifications such as transmission status, reset, associate, disassociate,

etc.

Digi XBee Manual

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