Kernel interface functions
The Kernel namespace implements interfaces to attach a function to some kernel events and also to read the kernel tick count.
Kernel namespace reference
Kernel::Clock example
The nested class Clock can be used to read the current RTOS kernel millisecond tick count as a C++11 Chrono time point. The below code snippet demonstrates use of Kernel::Clock to calculate the elapsed time:
/*
* Copyright (c) 2006-2020 Arm Limited and affiliates.
* SPDX-License-Identifier: Apache-2.0
*/
#include "mbed.h"
int main()
{
// 64-bit time doesn't wrap for half a billion years, at least
uint64_t now = Kernel::get_ms_count();
// wait a while
ThisThread::sleep_for(10);
uint64_t later = Kernel::get_ms_count();
//calculate millisecs elapsed
uint64_t elapsed_ms = later - now;
printf("Elapsed ms: %u \r\n", (uint32_t)elapsed_ms);
}
Kernel hooks example
You can use the function attach_idle_hook() to attach a function to be called by the RTOS idle task. You can use the function attach_thread_terminate_hook() to attach a function to be called when a thread terminates. The below code snippet demostrates the usage of these hooks.
/*
* Copyright (c) 2006-2020 Arm Limited and affiliates.
* SPDX-License-Identifier: Apache-2.0
*/
#include "mbed.h"
#include "Kernel.h"
/* Entry function for test thread */
void test_thread(void)
{
printf("\ntest thread started");
ThisThread::sleep_for(2000);
printf("\ntest thread exiting");
}
/* Hook function for thread terminate */
void thread_terminate_hook(osThreadId_t id)
{
printf("\ntest thread terminated");
}
/* Hook function for idle task */
void test_idle_hook(void)
{
printf("\nidle hook invoked\n");
//Now remove this hook and re-instate the original hook by passing a NULL for the idle hook funtion pointer
Kernel::attach_idle_hook(NULL);
}
// main() runs in its own thread in the OS
int main()
{
printf("\nattach_thread_terminate_hook demo:\n");
//Attach a hook for thread terminate event
Kernel::attach_thread_terminate_hook(thread_terminate_hook);
Thread *newThread = new Thread(osPriorityNormal1, 1024, NULL, NULL);
newThread->start(callback(test_thread));
ThisThread::sleep_for(4000);
printf("\n\nattach_idle_hook demo:\n");
//Attach a hook for idle task
Kernel::attach_idle_hook(test_idle_hook);
while (1) {
ThisThread::sleep_for(3000);
}
printf("\n\n");
}