MansOS Alarm

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Alarm

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#Basic

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#Advanced

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#Example

NOTE: This feature is not implemented as described currently. Older interface version exists.

Alarms are used to execute some code after a certain time period, possibly repeatedly. Note, that the number of timers is limited. Initially there are ALARM_COUNT timers available.

The more timers you run, the less precise they may be due to the possibility for several of them to fire at the same time. Only one callback function will be executed immediately, the rest of them will wait for the previous callback to finish and thus will be delayed.

Declared in:

#include "alarm.h"

Basic

Data types

AlarmId_t - Handle (ID) for identifying the alarm when calling the alarm procedures.

AlarmCb_t - Alarm callback function pointer. Points to a function that will be called when the alarm event occurs.

Constants

const AlarmId_t ALARM_FAIL = -1;        // Alarm operation failed. Returned by alarmNew()

Functions

AlarmId_t alarmNew( AlarmCb_t callbackFunction );

Creates a new, virtual alarm clock. Returns the ID for the new alarm. Returns ALARM_FAIL when no alarms are available. Sets the callback function. Note, that the number of concurrent alarms might be limited by the OS and platform.

void alarmStartOneShot( AlarmId_t id, uint16_t time_ms );

Starts the alarm in one-shot mode. Resets the alarm if it was already running. The alarm calls the callback function after the time in time_ms milliseconds is expired. Then it stops.

void alarmStartPeriodic( AlarmId_t id, uint16_t time_ms );

Starts the alarm in periodic mode. Resets the alarm if it was already running. The alarm calls the callback function after the time_ms is expired. Then it automatically restarts.

void alarmStop( AlarmId_t id );

Stops the alarm.

Advanced

Data types

AlarmType_t - Alarm types. These may be combined by "or"-ing or adding.

Constants

typedef enum {
  ALARM_ONESHOOT = 0x01,   // Fires the alarm once
  ALARM_REPEAT   = 0x02,   // Fires the alarm repeatedly until stopped
  ALARM_START    = 0x04,   // Starts the timer now.
} AlarmType_t;

Functions

int alarmUnused();

Returns the number of unused (free) alarms. This number is limited, especially on the platforms with very limited memory. Initially there are ALARM_COUNT alarms available.

void alarmSet( AlarmId_t id, AlarmType_t type, uint16_t time_ms )

Sets the alarm type and time delay in milliseconds. Do not start the alarm unless ALARM_START is added to the type. Stop the alarm if it is already running.

void alarmStart( AlarmId_t id );

Start the alarm. Resets the alarm if it was already running.

void alarmFree( AlarmId_t id );

Stops and releases the system resources associated with the alarm with this ID.

Example

#include "alarm.h"

bool myStartAlarm()
{
  AlarmId_t id = alarmNew( myAlarm );
  if( id == ALARM_FAIL ) return false;
  alarmStartPeriodic( id, 1000);  // Starts the timer now and fires every second
  return true;
}

AlarmCb_t myAlarm()
{
  LedsToggleRed();  // Blink the red LED
}