SX1232
WIRELESS & SENSING
DATASHEET
7.4. Top Sequencer: Listen Mode Examples
In this scenario, the circuit spends most of the time in Idle mode, during which only the RC oscillator is on. Periodically the
receiver wakes up and looks for incoming signal. If a wanted signal is detected, the receiver is kept on and data are
analyzed. Otherwise, if there was no wanted signal for a defined period of time, the receiver is switched off until the next
receive period.
During Listen mode, the Radio stays most of the time in a Low Power mode, resulting in very low average power
consumption. The general timing diagram of this scenario is given in Figure 43.
Listen mode : principle
Receive
Idle ( Sleep + RC )
Receive
Idle
Figure 43. Listen Mode: Principle
An interrupt request is generated on a packet reception. The user can then take appropriate action.
Depending on the application and environment, there are several ways to implement Listen mode:
Wake on a PreambleDetect interrupt
Wake on a SyncAddress interrupt
Wake on a PayloadReady interrupt
7.4.1. Wake on Preamble Interrupt
In one possible scenario, the sequencer polls for a Preamble detection. If a preamble signal is detected, the sequencer is
switched off and the circuit stays in Receive mode until the user switches modes. Otherwise, the receiver is switched off
until the next Rx period.
7.4.1.1. Timing Diagram
When no signal is received, the circuit wakes every Timer1 + Timer2 and switches to Receive mode for a time defined by
Timer2, as shown on the following diagram. If no Preamble is detected, it then switches back to Idle mode, i.e. Sleep mode
with RC oscillator on.
No received signal
Receive
Timer2
Idle ( Sleep + RC )
Timer1
Receive
Timer2
Idle
Timer1
Timer1
Figure 44. Listen Mode with No Preamble Received
Rev 3 - August 2012
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