main.cpp

00001 /* SIGNAL USAGES IN RTOS 
00002 What is Signal ?  - Answer : Remember these five points
00003 
00004 1) Signals are different from all the other types of kernel object in that they are not autonomous (user need to control or set - No automatioc control like semaphore)
00005 2) signals are associated with tasks/Threads and have no independent existence. 
00006 3) If signals are configured for an application, each task has a set of eight signal flags.
00007 
00008 4) Any task can set the signals of another task. Only the owner task can read the signals. 
00009 5) The read is destructive – i.e. the signals are cleared by the process of reading. No other task can read or clear a task’s signals.
00010 
00011 
00012 In below example there are two threads 1)main thread and 2)Thread that is connected with onBoard_led functions
00013 We set the signal from main thread ,  second thread received the signal and toggle the led state.
00014 
00015 Program name : LED BLINKING USING RTOS SIGNAL
00016 PLATFORM : STM NUCLEO 64 L476
00017 Created by : jaydeep shah
00018 email : radhey04ec@gmail.com
00019 */
00020 
00021 /* NOTE : WE ARE GOING TO USE EVENT FLAG CLASS METHOD The EventFlags class is used to control event flags or wait for event flags other threads control.
00022 */
00023 #include "mbed.h"
00024 #include "rtos.h"
00025  
00026 DigitalOut led(LED2);  //ON BOARD LED
00027  
00028 EventFlags event_flags;  // EVESNT FLAG OBJECT CREATED (DOMAIN : SIGNAL)
00029 
00030 //TASK which is related to signal 
00031 void onBoard_led() {
00032     uint32_t read = 0;  //CREATE VARIABLE TO STORE DATA
00033     while (true) {
00034         // Signal flags that are reported as event are automatically cleared -Autonomous object of Kernal
00035         
00036         read = event_flags.wait_any(0x1 | 0x2);
00037         if(read == 0x1)
00038         {
00039         led = !led;  //Toggle state
00040         }
00041         printf("\n Received this flag event 0x%08lx \n\r",read);
00042         
00043     }
00044 }
00045  
00046 int main (void) {
00047     Thread thread;  //create threaed
00048  
00049     thread.start(callback(onBoard_led));  //Thread start
00050  
00051     while (true) {
00052         ThisThread::sleep_for(1000); //sleep for 1 sec
00053         event_flags.set(0x1);  //set the signal for thread task from main thread  --LED BLINK TASK
00054         ThisThread::sleep_for(1000);
00055         event_flags.set(0x2); //This signal for print the statement -- use serial terminal
00056     }
00057 }