hello friends i have written the code for ARM RTOS, i have used same priority for all of my 4 task, its working fine
my problem is when i change the priority in the code then all task's are not executing simultaneously.... please any one help
But the buzzer doesn't sound like it have any reason at all to know anything about any other thread. It sounds like a thread that should sleep until another thread (anyone) does send an event: Please sound buzzer. Then it should either sound the buzzer for a fixed time, or until it gets an event "shut up". After that, it should start waiting again for an event to sound.
Or are your buzzer thread really intended to decide on the beeping itself? In that case, it doesn't need any events at all. It can just turn on - wait - turn off - wait - repeat.
The ADC should run continuously - it really shouldn't matter if the buzzer is on or off. But since you don't want to consume all CPU capacity for this, you either have to time slice the processor with other tasks of same priority or the ADC task must regularly sleep - sleep length depending on number of ADC updates/second.
The SPI thread shouldn't care about any ADC or buzzer - unless the LED patterns should change depending on ADC value or if the buzzer sounds or not. So just a loop that does what it should and either sleeps to reserve time for other threads or round-robin-schedules with similarly prioritized threads.
Not sure what POT values are. Meaning potentiometer values? As in values read in by the ADC thread? And what is the SCI protocol? Anyway - still a task that can run regularly either with round-robin scheduling or intentional delays to get x number of values sent every second.
Why don't you play with the examples Keil installs with the compiler? They clearly shows how to use the OS functions.
i should implement the program containing 4 task... i have 4 different external modules 1. BUZZER - To turn ON and OFF continuously 2. ADC() - To read the POT value and Display it on the LCD 3. SPI() - To send some sequences to LED PATTERNS continuously 4. SCI() - sending POT value again to the hyper terminal using SCI protocol
What is your goal? To have four tasks because your teacher have said that you should implement a program using an RTOS and containing 4 tasks. Or do you want four tasks because you have made an analysis of the problem and figured out that you have four different actions that needs to run concurrently in different combinations?
If additional tasks doesn't simplify the design then you either do something wrong or have a program that doesn't need tasks in the first place.
Look dude, this is getting a little out of hand. You code contains exactly that. Who writes your code? A slave? A patsy? Something?
now i am trying to execute the task3, but its not creating 3rd task itself
can any one tell me the procedure to start the task3 in different priority?
its continuously running the tsk2(because of higher prio) so i called some delay in tsk2 during that particular time its going to tsk1 am i right here?
Delays does not change the priority of tasks. A delay just removes the thread from the runnable list for a while, virtually making your system having one less task.
The scheduler always picks the highst prioritized thread that is runnable, i.e. not occupied by a delay, and not locked while waiting for a non-existing event or mail. When zero tasks are runnable, then the scheduler brings in the idle task - sometimes do-nothing code, but sometimes containing book keeping and cleaning up code potentially scanning the memory and flash for checksum errors etc.
Are you intentionally posting broken code, or are you not better than this?
/* 0x0004 represents bit 2. */ os_evt_wait_or(0x0001, 0xFFFF);
What does 0x0004 have with 0x0001 to do?
for (;;) { buzzer(); os_evt_set(0x0002,id2); //after completion of the buzzer operation going to the tsk2 /* Signal to task2 that task1 has compelted */ /* Wait for completion of task2 activity. */ /* 0xFFFF makes it wait without timeout. */ /* 0x0004 represents bit 2. */ os_evt_wait_or(0x0001, 0xFFFF); } }
So every time your unit boots, it should run buzzer first, and then wait for next buzzer event? Is that logical? Does the door bell at your home always sound once whenever the power company turns on the power?
And you seem to have tried to make task1 and task2 run every other time unconditionally. Isn't that very illogical? So you do one ADC read per activation of the buzzer? Exactly why should buzzer and ADC always run buzzer -> ADC -> buzzer -> ADC? Why not just have a single loop then with one call to buzzer and one call to ADC?
You do realize that the goal with multiple tasks are to prioritize things - letting high-priority tasks take over to perform the critical work before dropping out and returning the processor to lower-prioritized work? And to have multiple tasks because you want multiple things to happen semi-concurrently and normally at individual speeds.
A higher priority task can take the ownership of the CPU. So you don't need any task to wait for another task to finish.
The only really practical reason to implement two tasks that runs in lockstep is when you have a typical producer/consumer situation. The consumer sits and waits until the producer have produced something. The producer signals "data available" and the consumer wakes up, picks up the produced work and performs further processing of it. As soon as the consumer don't have any more data to work on, it goes down to sleep again, waiting for the producer to produce more. But your code is not an example of any producer/consumer. Just an attempt at converting a standard loop:
for (;;) { do_a(); do_b(); }
into something very much more complicated. You don't have any concurrency between do_a() and do_b() so, as written, the threads are not adding any functionality to your system.
What is concurrency then? Concurrency is when you do process ADC values and present on the LCD even when the buzzer is busy buzzing. Concurrency is when you scan a keyboard and process keyboard commands if the buzzer is buzzing or not. Concurrency is about making one task continue doing what it needs to do, while being as little affected as possible by other actions in the system - with the special case that tasks with critical priorities have the ability to jump in and take the processing capacity from tasks with high prio. And tasks with high prio can take the processor from tasks with medium or low prio. So tasks with low prio will only run when all tasks with medium, high or critical priority are sleeping, waiting for more input data or new events.
its solved i was again waiting their using wait flag it was not occurring just i removed that i.e.
__task void task1 (void){ /* Obtain own system task identification number */ id1 = os_tsk_self(); os_tsk_prio_self(1); /* Create task2 and obtain its task identification number */ id2 = os_tsk_create (task2, 2); for (;;) { buzzer();/* os_evt_set(0x0002,id2); /* Signal to task2 that task1 has compelted */ /* Wait for 50 ms before restarting task1 activity. */ // os_dly_wait(5); //I COMMENTED THIS PART NOW IT IS SWITCHING PROPERLY } }
in the end of the tsk2 i gave some delay(100msec) to switch/to jump/to go to tsk1.... but its not going to tsk1...... where i am going wrong please tell me .......
per, One way for a high-priority task to donate CPU time is to make use of delay/sleep calls, telling the OS that the thread don't need any CPU time for x time slices.
i used high priority for the tsk2, so to switch it from higher priority to lower priority i gave some delay.... am i right here?
Thank you for your active co-operation
i wrote here code for 2 task when the tsk1 is compleed its going for the tsk2..... and its not comming back to the tsk1
according to the above discution i gave some delay after tsk2 completion
__task void task1 (void){ /* Obtain own system task identification number */ id1 = os_tsk_self(); os_tsk_prio_self(1); /* Create task2 and obtain its task identification number */ id2 = os_tsk_create (task2, 2); for (;;) { buzzer(); os_evt_set(0x0002,id2); //after completion of the buzzer operation going to the tsk2 /* Signal to task2 that task1 has compelted */ /* Wait for completion of task2 activity. */ /* 0xFFFF makes it wait without timeout. */ /* 0x0004 represents bit 2. */ os_evt_wait_or(0x0001, 0xFFFF); } } __task void task2 (void) { for (;;) { /* Wait for completion of task1 activity. */ /* 0xFFFF makes it wait without timeout. */ /* 0x0004 represents bit 2. */ os_evt_wait_or(0x0002, 0xFFFF); ADC(); /* Signal to task1 if task2 has compelted */ os_evt_set(0x0001, id1); os_dly_wait(10); } } int main (void) { /* Start the RTX kernel, and then create and execute task1. */ os_sys_init(task1); }
Per,
It is really very nice that you are doing your best to help this guy. But really, the OP does not read our comments (at all!), clearly did not read the manuals (to which we have posted multiple links!) and is generally disoriented - maybe it is a language barrier. Just let him be: he simply refuses to make a minimal effort.
Do you have any reasons to believe that you need to change any scheduler options?
Note that if you do run threads with different priority, then you can't look at the scheduler and magically get it to handle your scheduling problems. Whenever you have multiple priorities, you (Y.O.U.) must write specific code for your specific threads that makes sure that the high-prio threads only runs when they have specific (high-priority) work to do and that whenever that high-priority work is done, you leave the CPU capacities for less prioritized threads.
Whenever you have multiple priorities, then the scheduler can only switch between ready (runnable) tasks of the highest priority. So your goal is to make sure that the highest prioritized threads are not in the state running or runnable for 100% of the time or your (Y.O.U.R) code will starve the less prioritized threads.
It doesn't matter if how long time slices you have or if you play with round-robin scheduling or not. Whenever you have multiple priorities involved, YOU must add schedulling code (sleeps or waits (events, mails, ...) into your threads to get them to cooperate. The RTOS does have the primitives you need for that work. It's like LEGO bricks, that you can combine. We can't do it for you - we don't even know what the goals are with your program.
The Keil samples do show examples of the use of the different OS functions. You can see how threads can sleep. You can see how threads turn over CPU time to threads of same priority. You can see how threads sets events or sends mails. You can see how threads sleeps until they get an event or mail. You can see how threads changes priorities (but don't be too quick to play with dynamic thread priorities).
The total number of functions available is quite low. So the total time needed to read through the manual pages and the related sample code is not so high. Have you spent such time yet? Do you have any specific questions after having read the documentation - specific sentences or paragraphs you don't understand?
What part of this statement don't you understand:
Read the user manual. Read the user manual. Read the user manual. Read the user manual. Read the user manual. Read the user manual.
!
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