Page 384 - ARM Based Microcontroller Projects Using MBED

370 15. Mbed RTOS PROJECTS

TABLE 15.1 Important Thread Functions
Function Description Example
join() Wait for a thread to terminate thread1.join()
terminate() Terminate a thread thread1.terminate()
set_priority() Set thread priority thread1.set_priority(osPriorityHigh)
get_priority() Get thread priority p¼thread1.get_priority()
wait() Wait specified milliseconds Thread::wait(100)
gettid() Get thread id of current thread t¼Thread::gettid()

READY: These are the threads which are ready to run. When the current thread
relinquishes the CPU the next thread with the highest priority will run.
WAITING: the threads that are waiting for some events are in this state.
INACTIVE: threads that are terminated or are not started are in this state. These threads do
not consume any CPU resources.

A WAITING thread can become READY or RUNNING when the event it is waiting for
becomes available. A RUNNING thread becomes WAITING if it waits for an event. A RUN-
NING thread becomes READY if a higher priority thread becomes RAEDY. A thread becomes
INACTIVE when it terminates.

15.4.8 Terminating Thread LEDAControl After 10 Flashes
Insomeapplicationswe maywanttoterminate anactive thread.Wecanforexamplemodify
the program given in Fig. 15.5 so that thread LEDAControl is terminated after 10s. The main
code for this new program is as follows the remainder of the program is same as in Fig. 15.5:

int main()
{
thread1.start(LEDAControl); // Start LEDAControl
thread2.start(LEDBControl); // Start LEDBControl
Thread::wait(10000); // Wait 10 seconds
thread1.terminate(); // Terminate LEDAControl
while(1);
}

15.4.9 Thread Callback

There are applications where we may want to pass parameters to a thread when the thread
is started. This is done using the callback function. An example program (program:
ThreadCallback) is shown in Fig. 15.6 where the flashing rate of the two LEDs are passed
as arguments to the two functions where LEDA flashing rate is 250ms and LEDB flashing
rate is 500ms. Note here that the addresses of the arguments must me passed to the functions
and the functions use pointers to read the data.