Manage End Devices Transmit RF data
Digi XBee® 3 Zigbee® RF Module
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input that is not at a valid high or low level can cause leakage depending on the temperature and
charge buildup that you may not observe at room temperature.
Transmit RF data
An end device may transmit data when it wakes from sleep and has joined a network. End devices
transmit directly to their parent and then wait for an acknowledgment to be received. The parent
performs any required address and route discoveries to help ensure the packet reaches the intended
destination before reporting the transmission status to the end device.
Receiving RF data
After waking from sleep, an end device sends a poll request to its parent to determine if the parent
has any buffered data for it. In pin sleep mode, the end device polls every 100 ms while the Sleep_RQ
pin is de-asserted (low). In cyclic sleep mode, the end device will only poll once before returning to
sleep unless the sleep timer (ST) is started (serial or RF data is received). If the sleep timer is started,
the end device will continue to poll every 100 ms until the sleep timer expires.
This firmware includes an adaptive polling enhancement where, if an end device receives RF data from
its parent, it sends another poll after a very short delay to check for more data. The end device
continues to poll at a faster rate as long as it receives data from its parent. This feature greatly
improves data throughput to end devices. When the end device no longer receives data from its
parent, it resumes polling every 100 ms.
I/O sampling
End devices can be configured to send one or more I/O samples when they wake from sleep. To
enable I/O sampling on an end device, the IR command must be set to a non-zero value, and at least
one analog or digital I/O pin must be enabled for sampling (D0 - D9, P0 - P4 commands). If I/O
sampling is enabled, an end device sends an I/O sample when it wakes and starts the ST timer. It will
continue sampling at the IR rate until the sleep timer (ST) has expired. For more information, see
Analog and digital I/O lines.
Wake end devices with the Commissioning Pushbutton
If you use D0 (DIO0/AD0/Commissioning Button Configuration) to enable the Commissioning
Pushbutton functionality, a high-to-low transition on the AD0/DIO0 pin (Micro pin 31/SMT pin 33/TH pin
20) causes an end device to wake for 30 seconds. For more information, see Commissioning
pushbutton and associate LED.
Parent verification
Since an end device relies on its parent to maintain connectivity with other devices in the network,
XBee end devices include provisions to verify the connection with its parent. End devices monitor the
link with their parent when sending poll messages and after a power cycle or reset event as described
below.
When an end device wakes from sleep, it sends a poll request to its parent. In cyclic sleep, if the end
device does not receive RF or serial data and the sleep timer is not started, it polls one time and
returns to sleep for another sleep period. Otherwise, the end device continues polling every 100ms. If
the parent does not send an acknowledgment response to three consecutive poll request
transmissions, the end device assumes the parent is out of range, and attempts to find a new parent.
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