FreeRTOS Support Archive
The FreeRTOS support forum is used to obtain active support directly from Real
Time Engineers Ltd. In return for using our top quality software and services for
free, we request you play fair and do your bit to help others too! Sign up
to receive notifications of new support topics then help where you can.
This is a read only archive of threads posted to the FreeRTOS support forum.
The archive is updated every week, so will not always contain the very latest posts.
Use these archive pages to search previous posts. Use the Live FreeRTOS Forum
link to reply to a post, or start a new support thread.
[FreeRTOS Home] [Live FreeRTOS Forum] [FAQ] [Archive Top] [June 2013 Threads]
hi
i wrote this program for test:
in port.c:
void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
void SIG_OUTPUT_COMPARE1A( void )
{
PORTA++;vPortYieldFromTick();PORTA--;
asm volatile ( "reti" );
}
=================================================================
/* Priority definitions for most of the tasks in the demo application. Some
tasks just use the idle priority. */
#define mainLED_TASK_PRIORITY( tskIDLE_PRIORITY )
void LED1( void *pvParameters )
{
DDRB = 0xff;
while(1)
{
PORTB |= (1<<0);
_delay_us(1);
PORTB &= ~(1<<0);
_delay_us(1);
}
}
void LED2( void *pvParameters )
{
DDRC = 0xff;
while(1)
{
PORTC |= (1<<1);
_delay_us(1);
PORTC &= ~(1<<1);
_delay_us(1);
}
}
portSHORT main(void)
{
DDRA=0xff;
PORTD++;
xTaskCreate( LED1, ( signed char * ) "LED1", 100, NULL, 0, NULL );
xTaskCreate( LED2, ( signed char * ) "LED2", 100, NULL, 0, NULL );
vTaskStartScheduler();
return 0;
}
note that i used PORTA to see timer interrupt flow.
after simulating i got this result on output:
you can see task1 (LED1) runs until first timer interrupt , and after first call of timer interrupt task switched to task2 (LED2) and it runs to ever.
i worked on it many hours and finally i found a way.
if you change timer interrupt in 'port.c' file to this :
void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
void SIG_OUTPUT_COMPARE1A( void )
{
asm volatile ( "sei" );
PORTA++;vPortYieldFromTick();PORTA--;
asm volatile ( "reti" );
}
you will see this result :
you can see that the program loops in interrupt handler until next interrupt tick and there are an overlap on firing interrupt.
but both task are working and we have auto switch between tasks.
I don't know what you are trying to do, what _delay_us() does (does it call a FreeRTOS function?), or what the "sei" instruction does, but the first thing I notice here is your calling PORTA++; from a naked function. That is probably not a good idea because the naked function will not have a stack frame of any kind, and it will change the MCU context before it has been saved. I would have to check the asm code generated by the compiler to be completely sure, but suspect it will break the scheduler.
Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.