AX-ConfigurationUtility User Manual
13
4.1.
Wake on Radio Mode (WOR)
In
Wake on Radio
mode the receiver periodically wakes up and searches the channel for
a signal. In absence of signal the receiver is switched off again immediately to save power.
If a signal is detected the receiver stays on and looks for a valid packet delimiter. The
Radio performs this task autonomously. Only after a valid packet has been received and
is waiting in the FIFO, the Radio wakes up the micro controller via an interrupt. A typical
application of this mode would be an infrequently operated remote control. The “
WOR
Settings” button opens the Wake on Radio panel:
Figure 1: Wake on Radio. WOR settings panel.
1.
This field configures how often the receiver wakes up and checks for signal. Waking
up less often reduces the average RX (idle) current. However, it increases the
necessary preamble length and average latency since the preamble needs to be at
least as long as the gap between two successive wake ups.
2.
The “enable RSSI threshold” option determines how the RX searches for signal upon
wake up:
a.
If this option is disabled, the RX directly scans for preamble pattern.
Sensitivity in this mode is comparable to continuous RX operation.
b.
If this option is enabled the RX first acquires an RSSI value. The scan for
preamble pattern is performed only if RF energy is detected. This reduces
current consumption (most notably at low data rates) since the RSSI
measurement is faster than the scan for preamble pattern. The drawback is
a reduction of sensitivity, since the RSSI threshold has to be set several dB
above
the
sensitivity
limit
to
prevent
false
positives.
The RX proceeds to scanning for preamble if RSSI > absolute threshold AND
RSSI >= (background RSSI + relative threshold). Background RSSI is the
RSSI average over past wake ups.
1.
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2.
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3.
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