István Cserny
In this example semaphores are used to ensure the running order of the program threads. Analogous to the relay race.
Revision 0:6d3407923be9, committed 2022-03-17
- Comitter:
- cspista
- Date:
- Thu Mar 17 12:38:12 2022 +0000
- Commit message:
- Final version
Changed in this revision
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Thu Mar 17 12:38:12 2022 +0000
@@ -0,0 +1,27 @@
+#include "mbed.h"
+#include "rtos.h"
+
+Semaphore sem[] = {(1),(0),(0),(0)}; // Set of semaphores
+DigitalOut led[] = {(D13),(D12),(D11),(D10)}; // Set of LEDs
+
+void led_thread(void const* args) {
+ int i = (int)args-1; // Idx of this task
+ int inext = (i+1)%4; // Idx of next task
+ while (true) {
+ sem[i].wait();
+ led[i] = 0; // ith LED on
+ Thread::wait(500+rand()%500);
+ led[i] = 1; // ith LED off
+ sem[inext].release(); // Start new task
+ }
+}
+
+int main (void) {
+ for(int i=0; i<4; i++) {
+ led[i]=1; // LEDs off
+ }
+ Thread t2(led_thread, (void *)2U);
+ Thread t3(led_thread, (void *)3U);
+ Thread t4(led_thread, (void *)4U);
+ led_thread((void *)1U);
+}
\ No newline at end of file
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed-rtos.lib Thu Mar 17 12:38:12 2022 +0000 @@ -0,0 +1,1 @@ +https://os.mbed.com/users/mbed_official/code/mbed-rtos/#5713cbbdb706
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed.bld Thu Mar 17 12:38:12 2022 +0000 @@ -0,0 +1,1 @@ +https://os.mbed.com/users/mbed_official/code/mbed/builds/65be27845400 \ No newline at end of file