Managing End Devices XBee End Device configuration
XBee/XBee-PRO ZigBee RF Modules User Guide 95
Sleep period
The sleep period is configured based on the SP, SN, and SO commands. The following table lists the behavior of
these commands.
The XBee module supports both a short cyclic sleep and an extended cyclic sleep that make use of these
commands. These two modes allow the sleep period to be configured according to the application requirements.
Short cyclic sleep
In short cyclic sleep mode, the sleep behavior of the module is defined by the SP and SN commands, and the SO
command must be set to 0x00 (default) or 0x02. In short cyclic sleep mode, the SP command defines the sleep
period and is settable up to 28 seconds. When the XBee enters short cyclic sleep, it remains in a low power state
until the SP time has expired.
After the sleep period expires, the XBee sends a poll request transmission to its parent to determine if its parent
has any buffered data waiting for the end device. Since router and coordinator devices can buffer data for end
device children up to 30 seconds, the SP range (up to 28 seconds) allows the end device to poll regularly enough
to receive buffered data. If the parent has data for the end device, the end device will start its sleep timer (ST) and
continue polling every 100 ms to receive data. If the end device wakes and finds that its parent has no data for it,
the end device can return to sleep immediately.
The SN command can be used to control when the On/Sleep line is asserted (high). If SN is set to 1 (default), the
On/Sleep line will be set high each time the XBee wakes from sleep. Otherwise, if SN is greater than 1, the On/
Sleep line will only be set high if RF data is received, or after SN wake cycles occur. This allows an external device
to remain powered off until RF data is received, or until a number of sleep periods have expired (SN sleep
periods). This mechanism allows the XBee to wake at regular intervals to poll its parent for data without waking
an external device for an extended time (SP * SN time). This is shown in the figure below.
DIN
A cyclic sleep end device enters sleep mode when no serial or RF data is received for ST time
ST = Time Awake
On/Sleep
Legend
On/Sleep
Transmitting Poll
Request
Command Range Description
SP
0x20 - 0xAF0 (x 10 ms)
(320 - 28,000 ms)
Configures the sleep period of the module.
SN
1 - 0xFFFF Configures the number of sleep periods multiplier.
SO
0 - 0xFF Defines options for sleep mode behavior.
0x02 - Always wake for full ST time
0x04 - Enable extended sleep (sleep for full (SP * SN) time)
To Next Page
Loading...
Need help?
General
