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Low power and battery life
Asynchronous pin sleep (SM = 1).
n
Pin sleep allows an external microcontroller to determine when the device should sleep and
when it should wake by controlling the Sleep_RQ pin (pin 9). When Sleep_RQ is asserted (high)
by connecting it to 3.3 volts, the device will finish any operation and enter a low power state.
The device wakes when the Sleep_RQ pin is de-asserted (low).
Asynchronous cyclic sleep (SM = 4).
n
Cyclic sleep allows the module to sleep for a specified time (SP) and wake for a short time (ST)
before returning to sleep again.
If the device receives serial or wireless data while awake, it extends the time before it returns
to sleep by the amount specified by the ST parameter. Otherwise, it enters sleep mode
immediately.
The SO, SN, SP and ST parameters control the sleep cycle; see
Asynchronous cyclic sleep with pin wake-up (SM = 5).
n
The cyclic sleep with pin wake up is a slight variation of the cyclic sleep mode that allows the
device to be woken prematurely by de-asserting the Sleep_RQ pin. The module will not sleep
when the Sleep_RQ is de-asserted.
The SO, SN, SP and ST parameters control the sleep cycle (See,
Note
To learn more about asynchronous sleep networks, go to the
Modules User
Guide.
Synchronous sleep
The synchronous sleep feature of DigiMesh makes it possible for all nodes in the network to
synchronize their sleep and wake times. All synchronized cyclic sleep nodes enter and exit a low power
state at the same time, forming a cyclic sleeping network. Nodes synchronize by receiving a special
wireless packet called a sync message sent by a node acting as a sleep coordinator. This allows some
or all XBee modules in the network to be battery powered.
Synchronous sleep operation
All modules go to sleep at the same time. This forms a cyclic sleeping network where we can define
two different device types: sleep coordinator and sleeping router.
Sleep coordinator
A node in the DigiMesh network acts as the sleep coordinator. This device:
Defines the sleeping parameters for the entire network: sleep and wake times for every
n
cycle.
Broadcasts a synchronization message at the beginning of each wake period.
n
Cannot sleep.
n
A node in the network can become a coordinator through a nomination and election process.
Sleeping router
XBee-PRO 900HP DigiMesh Kit User Guide
Synchronous sleep
Configuration
Parameters.
Configuration
Parameters).
XBee-PRO 900HP and XSC RF
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