Digi XBee, Руководство пользователя, Страница: 137 / 307

Manage End Devices Transmitting RF data
XBee/XBee-PRO® S2C ZigBee® RF Module 137
Internal pin pull-ups
Internal pin pull-ups can pull excess current and cause the sleep current readings to be higher than
desired if you drive or float the pull-ups.
n
Disable all pull-ups for input lines that have a low driven state during sleep.
n
Enable pull-ups for floating lines or inputs that do not connect to other circuitry.
If you use an analog-to-digital converter (ADC) to read the analog voltage of a pin, it may not be
possible to stop all leakage current unless you can disconnect the voltage during sleep. Each floating
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.
Transmitting 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 100ms 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.