I have created many timers in my running application.
At a certain point, I want to check whether a previously created timer is active or not.
pthread_create - creating the timer
timer_settime - starting the timer (recursive timer)
Now somewhere in the application and using the timer id, I will want to check whether that timer is active or not.
Is there an API to do this? If not, How can I do this?
Possible way I was thinking:
-Issue two consecutive timer_gettime() and see if there is any change for the given timer id.
-If there is change, I will consider that as an active timer.
Related
I'm working on an application in Windows CVI that needs to run some code for a series of time intervals set by the user via text entry boxes. The boxes include three for how long to run each process, one to show the total time the processes will take, and one to show the time remaining.
My implementation currently is to have a function with static variables to track which process is running and how long is left in the current process, then move on when that time has elapsed. This function triggers on pushing a start button. Unfortunately, the code stops on the click of the start button as it seems to be waiting for the code to finish executing before it allows any further inputs.
Is there a "right" way to do this? Maybe something with multithreading or a pre-built timer application?
Got an answer here: "You are on the right way speaking about timers: place a timer control on your panel, set it to disabled, put your code in the timer callback and run the program. When the user inputs the required time, set the ATTR_INTERVAL attribute of the timer to this value, next enable the timer with ATRT_ENABLED attribute and you'll have your timed function up and running!"
Hi I want to toggle LED with timing as follows
100ms ON1, 250ms Off1
1250ms ON2, 1500ms off2
and this cycle gets repeated (Both ON1 off1 and ON2 off2 pair repeats)
For this I have planned to utilize hardware timer with elapsing timings as 100,250,1250 and 1500 and this will repeat.
I am pretty new to the embedded field,
My questions are as follows
How to trigger this using a hardware timer? (How to enable and alternate the timings dynamically?)
How to set a call back function that toggles LED based on the timer elapse ?
Note : This is not a standalone code but an application will
Be running .From OS the callback will be triggered in the background so that other normal application is not affected during this process
Use the OS's software timer service. Create four software timers with the specified periods. The timers should be configured to count once and then stop each time they are started (i.e., they should be "one-shot", not "auto-reloading" nor "continuous" or whatever terminology your OS uses). Each software timer will have a unique callback function that you specify when you create the software timer.
From main, or wherever is appropriate, start the first timer once to get things started. Then start the second timer from the first timer's callback function. And start the third timer from the second timer's callback function. And so on until the last timer's callback function restarts the first timer and the circle of timers repeats.
Use timer interrupt for it.
You have the ready example here:
https://www.diymat.co.uk/arm-blinking-led-driver/
It does what you need and a bit more as well :)
I'm learning libev and I've stumbled upon this question. Assume that I want to process something as soon as possible but not now (i.e. not in the current executing function). For example I want to divide some big synchronous job into multiple pieces that will be queued so that other callbacks can fire in between. In other words I want to schedule a callback with timeout 0.
So the first idea is to use ev_timer with timeout 0. The first question is: is that efficient? Is libev capable of transforming 0 timeout timer into an efficient "call as soon as possible" job? I assume it is not.
I've been digging through libev's docs and I found other options as well:
it can artificially delay invoking the callback by using a prepare or idle watcher
So the idle watcher is probably not going to be good here because
Idle watchers trigger events when no other events of the same or higher priority are pending
Which probably is not what I want. Prepare watchers might work here. But why not check watcher? Is there any crutial difference in the context I'm talking about?
The other option these docs suggest is:
or more sneakily, by reusing an existing (stopped) watcher and pushing it into the pending queue:
ev_set_cb (watcher, callback);
ev_feed_event (EV_A_ watcher, 0);
But that would require to always have a stopped watcher. Also since I don't know a priori how many calls I want to schedule at the same time then I would have to have multiple watchers and additionally keep track of them via some kind of list and increase it when needed.
So am I on the right track? Are these all possibilities or am I missing something simple?
You may want to check out the ev_prepare watcher. That one is scheduled for execution as the last handler in the given event loop iteration. It can be used for 'Execute this task ASAP' implementations. You can create dedicated watcher for each task you want to execute, or you can implement a queue with a one prepare watcher that is started once queue contains at least one task.
Alternatively, you can implement similar mechanism using ev_idle watcher, but this time, it will be executed only if the application doesn't process any 'higher priority' watcher handlers.
I am working on some Linux applications that uses timers.I need to change the timer interval during runtime.So is there any API that could detect whether any previous timer is running or not.My idea is like i will detect any previous running timer and will delete it and then will re-create the timer with new time value.
I am using timer_create(),timer_settime() for timer creation and timer starting.
Thanks&Regards
Amit Kumar
From the man page:
(If the timer was already armed, then the previous settings are overwritten.)
Seems like the function already does what you are looking for.
I got a special question regarding timer boundary events on a user task in Activiti/Camunda:
When starting the process I set the timer duration with a process variable and use expressions in the boundary definition to resolve the variable. The boundary event is defined on a user task.
<bpmn2:timerEventDefinition id="_TimerEventDefinition_11">
<bpmn2:timeDuration xsi:type="bpmn2:tFormalExpression">${hurry}</bpmn2:timeDuration>
</bpmn2:timerEventDefinition>
In some cases, when the timer is already running it can occur, that the deadline (dueDate) should be extended because the asignee has requested more time. For this purpose i want to change the value of the process variable defining the deadline.
As it happens, the variable is already resolved at the process-start and set to the boundary event.
Any further changes of the variable do not affect the dueDate of the boundary timer because it is stored in the database and is not updated when the value of the variable changes.
I know how to update the dueDate of the job element via the Java API, but i want to provide a generic approach like setting it with changing the value of the variable.
The most common use case for extending the deadline will be when the boundary timer is already running.
Any ideas how to cope with this problem?
Any tips are very apprechiated.
Cheers Chris
After some time of thinking I came up with a workaround like that:
I start the process with two variables. "hurry" is evaluated for the boundary timer. And "extendDeadline" is initialized with false. If the timer triggers and the process advances to the exclusive gateway, the value of "extendDeadline" is evaluated.
If a user has changed the value of "extendDeadline" to true during the the timer was running the process returns to the user task again where the boundary timer is set to the value of "hurry".
If the "extendDeadline" is still set to false, the process can proceed.
If the timer is running you can change dueDate of the timer by executing a signal. If a assginee requested more time, set new value of hurry and execute the signal. The old timer will be canceled and the new timer will be created with new due date.
runtimeService.setVariable(execution.getId(), "hurry", newDueDate);
runtimeService.signalEventReceived(signalName, execution.getId());
Solution is to have 2 out going sequence flow, one should be from boundary timer on task and another one should be from task it self, as shown in diagram added by #theFriedC. See following image also.
Then you can use some exclusive gateway on 2nd sequence flow and reroute that back to same task with a new timer value.