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
get_ms_count() example
The function get_ms_count() can be used to read the current RTOS kernel millisecond tick count. The below code snippet demonstrates use of the get_ms_count() function to calculate the elapsed time:
void send_data()
{
// 64-bit time doesn't wrap for half a billion years, at least
uint64_t now = Kernel::get_ms_count();
//do some operations
// ...
uint64_t later = Kernel::get_ms_count();
//calculate millisecs elapsed
uint64_t elapsed_ms = later - now;
}
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.
/* mbed Microcontroller Library
* Copyright (c) 2018 ARM Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "mbed.h"
#include "Kernel.h"
/* Entry function for test thread */
void test_thread(void)
{
printf("\ntest thread started");
wait(2.0);
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, 512, NULL, NULL);
newThread->start(callback(test_thread));
wait(4.0);
printf("\n\nattach_idle_hook demo:\n");
//Attach a hook for idle task
Kernel::attach_idle_hook(test_idle_hook);
while(1) {
wait(3.0);
}
printf("\n\n");
}