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Building Wireless Sensor Networks by Robert Faludi

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ZigBee Transmit Request

Let’s send some real data! This frame is how you tell your local radio to send information to some other remote radio. The ZigBee Transmit Request frame encapsulates your payload information (the data itself) with a batch of addressing and transmission options that describe how the payload should be delivered. This frame is a great example of how API mode facilitates something that can’t easily be accomplished in transparent/command mode: setting destination addresses on the fly. Now instead of issuing a +++ and a bunch of commands each time we want to change the destination address, we simply attach that destination to each a frame of data and send it on its way. This is a much more efficient process, especially if you have a network with hundreds of different nodes that you might need to use as destinations. Table 5-5 shows the ZigBee Transmit Request format.

Table 5-5. API format for ZigBee Transmit Request

Frame fields

Offset

Example

Description

Start delimiter

 

0

0x7E

 

Length

 

MSB 1

0x00

Number of bytes between the length and the checksum.

 

LSB 2

0x16

Frame-specific data

Frame type

3

0x10

 
 

Frame ID

4

0x01

Identifies the UART data frame for the host to correlate with a subsequent ACK (acknowledgment). If set to 0, no response is sent.

64-bit destination address

MSB 5

0x00

Set to the 64-bit address of the destination device. The following addresses are also supported:

0x0000000000000000 – Reserved 64-bit address for the coordinator.

0x000000000000FFFF ...

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