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
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?
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?
Look dude, this is getting a little out of hand. You code contains exactly that. Who writes your code? A slave? A patsy? Something?
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.
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
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.
In this program SCI() function will Read the ADC(POT) value(of the same ADC) and displays on the Hyper terminal
per, i am sorry......... i m not understanding this
www.keil.com/.../rlarm_os_evt_wait_or.htm
function................
i have the example code . i am not able to understand please help example code:
/************************************************************/ /* PROJECT NAME: Events */ /* Project: Introduction to RL-ARM */ /* Engineer: T Martin tmartin@hitex.co.uk */ /* Filename: main.c */ /* Language: C */ /* Compiler: Real View 3.4 */ /* Assembler: */ /* O/S: RL-ARM 3.4 */ /************************************************************/ /* COPYRIGHT: Hitex UK Ltd 2007 */ /* LICENSE: THIS VERSION CREATED FOR FREE DISTRIBUTION */ /************************************************************/ /* Function: */ /* */ /* Example */ /* */ /* Demonstrates the handeling of event flags in RTL RTOS */ /* */ /* Oscillator frequency 12.000 Mhz */ /* Target board Keil MCB23000 */ /************************************************************/ #include <rtl.h> #include <LPC23xx.H> #include "LCD.h" void LED_Init(void); void LED_On (unsigned int num); void LED_Off (unsigned int num); void task1 (void); // Function prototypes for tasks void task2 (void); void task3 (void); void task4 (void); OS_TID tsk1,tsk2,tsk3,tsk4; //Define Task-ID variables int main (void) { LED_Init(); lcd_init(); //Setup the LCD display lcd_clear(); lcd_print (" Event "); os_sys_init (task1); //Start the RTX with task1 } __task void task1 (void) //define function as task { tsk1 = os_tsk_self(); //Get Task 1 Handle tsk2 = os_tsk_create(task2,1); //create tasks tsk3 = os_tsk_create(task3,1); tsk4 = os_tsk_create(task4,1); while(1) { os_evt_wait_or(0x0005,0xffff); //Wait for an event to be set, no time out set_cursor (0, 1); //Print running task to LCD lcd_print (" Task 1 "); LED_On(0x01); //Switch on an LED to how the task has run os_dly_wait(50); os_evt_set(0x0001,tsk2); //Set an event for task 2. Each task has 16 event flags os_evt_set(0x0001,tsk3); //Set an event in task 3 } } __task void task2 (void) { while(1) { os_evt_wait_or(0x0001,0xffff); //Wait for an event set_cursor (0, 1); //Print running task to LCD lcd_print (" Task 2 "); LED_On(0x02); //Switch on an LED to how the task has run os_dly_wait(50); os_evt_set(0x0002,tsk3); //Set an event in Task 3 } } __task void task3 (void) { while(1) { os_evt_wait_and(0x0003,0xffff); // Wait for two event flags to be set set_cursor (0, 1); //Print running task to LCD lcd_print (" Task 3 "); LED_On(0x04); //Switch on an LED to how the task has run os_dly_wait(50); LED_Off(0x07); //Clear the led's os_dly_wait(100); //Delay os_evt_set(0x0001,tsk1); //Trigger task 1 to start over } } __task void task4 (void) { os_evt_set(0x0001,tsk1); //Set an event in task 1 to kick off with os_tsk_delete_self(); //Delete the task } void LED_Init(void) { PINSEL10 = 0; // Disable ETM interface, enable LEDs FIO2DIR = 0x000000FF; // P2.0..7 defined as Outputs FIO2MASK = 0x00000000; } // Function that turns on requested LED void LED_On (unsigned int num) { FIO2SET |= num; } // Function that turns off requested LED void LED_Off (unsigned int num) { FIO2CLR |= num; }
ABSTRACT:
This example demonstrates the use of event flags to trigger execution of tasks
The project consists of four tasks
tasks 1 -3 wait for one of their event flags to be set
task four sets the event flag of task1 and then deletes itself
task 1 switches on led 1 and then sets the event flag of task two
task two switches on led two and sets the event flag of task three
task 3 switches on LED three waits for a period then switches off all LEDs and then sets the event flag of task one and the sequence restarts. .......................................................................................... in the above he used event flags as 5,1,3, for each task, what are these events? how the event flag will set?
Everything (basically) is explained by the return value of the function (as described in the manual): OS_R_EVT At least one of the flags specified by wait_flags has been set. OS_R_TMO The timeout has expired.
So a task may wait for flag 1 or flag 2 or flag 3 or flag 4 or flag 5 or ... and will wake when one or more of the flags it waits for (the reason it has an "or" in the name, as in event 1 _or_ event 2 _or_ event 3 ...) gets set, or after a timeout, i.e. having waited too long without anyone setting one of the event flags.
So how to set an event? Don't you think the function os_evt_set(flags,task) does that? Why else would the function be named "evt" and "set"?
The events are nothing more than flags. You decide what each flag stands for. The OS doesn't care. You may decide that bit 0 is "one more beer please" while bit 1 is "please self-destroy". So if you have 16 flags, then you can signal up ti 16 different events and the receiving task can decide which of these 16 events it is interested in servicing.
Alas, that school project is quite meaningless since it doesn't contain any concurrency. It's just a state machine that could have been implemented in a single task like:
for (;;) { do_task1(); do_task2(); do_task3(); }
But alas, not all teachers do give meaningful exercises. It would have been so very much better if one of the tasks had continued doing what it was expected to do, while it requested another task to perform a different job concurrently and then signal back when that other job was done.
Thank you per
if i set the flag 1 in task1 , it means that i should wait for that perticular flag(flag 1) in task2?
example:
__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 (;;) { /* Signal to task2 that task1 has compelted */ os_evt_set(0x0004, id2); setting the flag here /* Wait for completion of task2 activity. */ /* 0xFFFF makes it wait without timeout. */ os_evt_wait_or(0x0003, 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(0x0004, 0xFFFF); should i wait here for same flag? /* Signal to task1 that task1 has compelted */ os_evt_set(0x0003, id1); } }
"if i set the flag 1 in task1 , it means that i should wait for that perticular flag(flag 1) in task2?"
That obviously depends on if your goal is that task 1 should activate task 2.
If task 2 have (at least) same priority unless you put task 1 to sleep after having set the event. As usual, the OS will sort all runnable (not waiting for a delay to end or waiting for event, mail,...) on priority and only look at the threads that have the highest priority among the threads that are running. Threads with lower priority gets ignored. Threads still waiting for something that haven't happened (no timeout , no event, no mail, ...) gets ignored.
Thank you so much per.....
now i resided to change my project procedure
i want ADC to read the value for some time and display it on the LCD as well as Hyper terminal(using SCI protocol), buzzer should be turned ON and OFF according to events(as you mentioned earlier) is it possible?? and what about the SPI() function where shall i put? and for what reason? OR should i develop it in different way? if so please suggest me..
Excuse me, but I believe most of us here are working right now. Can't you find a consultant (=pay) to do your homework for you?
in the below program its switching from tsk1 to tsk2 and tsk2 to tsk3 but its again not going back to the tsk1 where tsk2 is going in to wait state.... can anyone tell me why tsk3 is not going to the wait state?
__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); id3 = os_tsk_create (task3, 3); for (;;) { buzzer();/* ... place code for task1 activity here ... */ os_evt_set(0x0002,id2); /* Signal to task2 that task1 has compelted */ os_evt_wait_or(0x0001,0xffff); } } __task void task2 (void) { for (;;) { ADC();/* ... place code for task2 activity here ... */ //os_evt_set(0x0003, id3); os_evt_wait_or(0x0002, 0xFFFF); //os_dly_wait(10); } } __task void task3(void) { for(;;) { SPI(); /* Signal to task1 that task1 has compelted */ os_evt_set(0x0001, id1); os_evt_wait_or(0x0003,0xffff); os_dly_wait(15); } } int main (void) { /* Start the RTX kernel, and then create and execute task1. */ os_sys_init(task1); }
We don't even know if buzzer(), ADC() or SPI() takes long time in relation to os_dly_wait(15).
You have done some debugging, haven't you? What happens when you singlestep the three threads?
By the way - task 3 is waiting for os_evt_wait_or(0x0003,0xffff). But who is sending any event 0x0001 or 0x0002 to this thread? How long do you think the wait will be if the thread don't get anyone to set one or both of the events?
Another thing - is there are reason why task 3 listens to two flags?