Interruptions - Libelium Waspmote Technical Manual

5. Interruptions

Interruptions are signals received by the microcontroller which indicate it must stop the task is doing to attend to an event that
has just happened. Interruption control frees the microcontroller from having to control sensors all the time. It also makes the
sensors warn Waspmote when a determined value (threshold) is reached.
Figure: Diagram of mode in Waspmote
Waspmote is designed to work with 2 types of interruptions: Synchronous and asynchronous
• Synchronous Interruptions
They are programmed by timers. They allow to program when we want them to be triggered. There are two types of timer
alarms: periodic and relative.
- Periodic Alarms are those to which we specify a particular moment in the future, for example: "Alarm programmed for
every fourth day of the month at 00:01 and 11 seconds", they are controlled by the RTC.
Relative alarms are programmed taking into account the current moment, eg: "Alarm programmed for 5 minutes and 10
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seconds", they are controlled through the RTC and the microcontroller's internal Watchdog.
• Asynchronous Interruptions
These are not programmed so it is not known when they will be triggered. Types:
Sensors: the sensor boards can be programmed so that an alarm is triggered when a sensor reaches a certain threshold.
-
Accelerometer: The accelerometer that is built into the Waspmote can be programmed so that certain events such as
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a fall or change of direction generate an interruption.
- XBee module (Digimesh protocol only): Digimesh protocol allows the XBee to set cyclic sleep modes which can
interrupt Waspmote each time the module wakes up. This permits to set up cyclic sleep networks. So, Digimesh XBees
can wake up when certain internal timeout expires (however not when other node sends frames).
All interruptions, both synchronous and asynchronous can wake Waspmote up from the Sleep and the Deep Sleep mode.
However, only the synchronous interruption by the RTC is able to wake it up from the Hibernate mode.
The Hibernate mode totally disconnects the Waspmote power, leaving only the battery powering the RTC to wake Waspmote
up when the time alarm is reached. Because of this disconnection, when the RTC generates the corresponding alarm, the power
in Waspmote is reconnected and the code starts again from the setup.
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Interruptions
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