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port.c
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port.c
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/*
FreeRTOS V8.2.3 - Copyright (C) 2015 Real Time Engineers Ltd.
All rights reserved
VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
This file is part of the FreeRTOS distribution.
FreeRTOS is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License (version 2) as published by the
Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
***************************************************************************
>>! NOTE: The modification to the GPL is included to allow you to !<<
>>! distribute a combined work that includes FreeRTOS without being !<<
>>! obliged to provide the source code for proprietary components !<<
>>! outside of the FreeRTOS kernel. !<<
***************************************************************************
FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. Full license text is available on the following
link: http://www.freertos.org/a00114.html
***************************************************************************
* *
* FreeRTOS provides completely free yet professionally developed, *
* robust, strictly quality controlled, supported, and cross *
* platform software that is more than just the market leader, it *
* is the industry's de facto standard. *
* *
* Help yourself get started quickly while simultaneously helping *
* to support the FreeRTOS project by purchasing a FreeRTOS *
* tutorial book, reference manual, or both: *
* http://www.FreeRTOS.org/Documentation *
* *
***************************************************************************
http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
the FAQ page "My application does not run, what could be wrong?". Have you
defined configASSERT()?
http://www.FreeRTOS.org/support - In return for receiving this top quality
embedded software for free we request you assist our global community by
participating in the support forum.
http://www.FreeRTOS.org/training - Investing in training allows your team to
be as productive as possible as early as possible. Now you can receive
FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
Ltd, and the world's leading authority on the world's leading RTOS.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool, a DOS
compatible FAT file system, and our tiny thread aware UDP/IP stack.
http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
licenses offer ticketed support, indemnification and commercial middleware.
http://www.SafeRTOS.com - High Integrity Systems also provide a safety
engineered and independently SIL3 certified version for use in safety and
mission critical applications that require provable dependability.
1 tab == 4 spaces!
*/
#include <stdlib.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/wdt.h>
#include "FreeRTOS.h"
#include "task.h"
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the AVR port.
*----------------------------------------------------------*/
/* Start tasks with interrupts enabled. */
#define portFLAGS_INT_ENABLED ( (StackType_t) 0x80 )
#if defined( portUSE_WDTO)
#warning "Watchdog Timer used for scheduler."
#define portSCHEDULER_ISR WDT_vect
#elif defined( portUSE_TIMER0 )
/* Hardware constants for Timer0. */
#warning "Timer0 used for scheduler."
#define portSCHEDULER_ISR TIMER0_COMPA_vect
#define portCLEAR_COUNTER_ON_MATCH ( (uint8_t) _BV(WGM01) )
#define portPRESCALE_1024 ( (uint8_t) (_BV(CS02)|_BV(CS00)) )
#define portCLOCK_PRESCALER ( (uint32_t) 1024 )
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( (uint8_t) _BV(OCIE0A) )
#define portOCRL OCR0A
#define portTCCRa TCCR0A
#define portTCCRb TCCR0B
#define portTIMSK TIMSK0
#define portTIFR TIFR0
#elif defined( portUSE_TIMER1 )
/* Hardware constants for Timer1. */
#warning "Timer1 used for scheduler."
#define portSCHEDULER_ISR TIMER1_COMPA_vect
#define portCLEAR_COUNTER_ON_MATCH ( (uint8_t) _BV(WGM12) )
#define portPRESCALE_64 ( (uint8_t) (_BV(CS11)|_BV(CS10)) )
#define portCLOCK_PRESCALER ( (uint32_t) 64 )
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( (uint8_t) _BV(OCIE1A) )
#define portOCRL OCR1AL
#define portOCRH OCR1AH
#define portTCCRa TCCR1A
#define portTCCRb TCCR1B
#define portTIMSK TIMSK1
#define portTIFR TIFR1
#elif defined( portUSE_TIMER2 )
/* Hardware constants for Timer2. */
#warning "Timer2 used for scheduler."
#define portSCHEDULER_ISR TIMER2_COMPA_vect
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( (uint8_t) _BV(OCIE2A) )
#define portOCRL OCR2A
#define portTCCRa TCCR2A
#define portTCCRb TCCR2B
#define portTIMSK TIMSK2
#define portTCNT TCNT2
#define portTIFR TIFR2
#elif defined( portUSE_TIMER3 )
/* Hardware constants for Timer3. */
#warning "Timer3 used for scheduler."
#define portSCHEDULER_ISR TIMER3_COMPA_vect
#define portCLEAR_COUNTER_ON_MATCH ( (uint8_t) _BV(WGM32) )
#define portPRESCALE_64 ( (uint8_t) (_BV(CS31)|_BV(CS30)) )
#define portCLOCK_PRESCALER ( (uint32_t) 64 )
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( (uint8_t) _BV(OCIE3A) )
#define portOCRL OCR3AL
#define portOCRH OCR3AH
#define portTCCRa TCCR3A
#define portTCCRb TCCR3B
#define portTIMSK TIMSK3
#define portTIFR TIFR3
#endif
/*-----------------------------------------------------------*/
/* We require the address of the pxCurrentTCB variable, but don't want to know
any details of its type. */
typedef void TCB_t;
extern volatile TCB_t * volatile pxCurrentTCB;
/* actual number of ticks per second, after configuration. Not for RTC, which has 1 tick/second. */
TickType_t portTickRateHz;
/* remaining ticks in each second, decremented to enable the system_tick. Not for RTC, which has 1 tick/second. */
volatile TickType_t ticksRemainingInSec;
/*-----------------------------------------------------------*/
/*
* Perform hardware setup to enable ticks from timer compare match A.
*/
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/
/*
* Macro to save all the general purpose registers, the save the stack pointer
* into the TCB.
*
* The first thing we do is save the flags then disable interrupts. This is to
* guard our stack against having a context switch interrupt after we have already
* pushed the registers onto the stack - causing the 32 registers to be on the
* stack twice.
*
* r1 is set to zero as the compiler expects it to be thus, however some
* of the math routines make use of R1.
*
* The interrupts will have been disabled during the call to portSAVE_CONTEXT()
* so we need not worry about reading/writing to the stack pointer.
*/
#if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__)
/* 3-Byte PC Save */
#define portSAVE_CONTEXT() \
__asm__ __volatile__ ( "push r0 \n\t" \
"in r0, __SREG__ \n\t" \
"cli \n\t" \
"push r0 \n\t" \
"in r0, 0x3b \n\t" \
"push r0 \n\t" \
"in r0, 0x3c \n\t" \
"push r0 \n\t" \
"push r1 \n\t" \
"clr r1 \n\t" \
"push r2 \n\t" \
"push r3 \n\t" \
"push r4 \n\t" \
"push r5 \n\t" \
"push r6 \n\t" \
"push r7 \n\t" \
"push r8 \n\t" \
"push r9 \n\t" \
"push r10 \n\t" \
"push r11 \n\t" \
"push r12 \n\t" \
"push r13 \n\t" \
"push r14 \n\t" \
"push r15 \n\t" \
"push r16 \n\t" \
"push r17 \n\t" \
"push r18 \n\t" \
"push r19 \n\t" \
"push r20 \n\t" \
"push r21 \n\t" \
"push r22 \n\t" \
"push r23 \n\t" \
"push r24 \n\t" \
"push r25 \n\t" \
"push r26 \n\t" \
"push r27 \n\t" \
"push r28 \n\t" \
"push r29 \n\t" \
"push r30 \n\t" \
"push r31 \n\t" \
"lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"in r0, 0x3d \n\t" \
"st x+, r0 \n\t" \
"in r0, 0x3e \n\t" \
"st x+, r0 \n\t" \
);
#else
/* 2-Byte PC Save */
#define portSAVE_CONTEXT() \
__asm__ __volatile__ ( "push r0 \n\t" \
"in r0, __SREG__ \n\t" \
"cli \n\t" \
"push r0 \n\t" \
"push r1 \n\t" \
"clr r1 \n\t" \
"push r2 \n\t" \
"push r3 \n\t" \
"push r4 \n\t" \
"push r5 \n\t" \
"push r6 \n\t" \
"push r7 \n\t" \
"push r8 \n\t" \
"push r9 \n\t" \
"push r10 \n\t" \
"push r11 \n\t" \
"push r12 \n\t" \
"push r13 \n\t" \
"push r14 \n\t" \
"push r15 \n\t" \
"push r16 \n\t" \
"push r17 \n\t" \
"push r18 \n\t" \
"push r19 \n\t" \
"push r20 \n\t" \
"push r21 \n\t" \
"push r22 \n\t" \
"push r23 \n\t" \
"push r24 \n\t" \
"push r25 \n\t" \
"push r26 \n\t" \
"push r27 \n\t" \
"push r28 \n\t" \
"push r29 \n\t" \
"push r30 \n\t" \
"push r31 \n\t" \
"lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"in r0, 0x3d \n\t" \
"st x+, r0 \n\t" \
"in r0, 0x3e \n\t" \
"st x+, r0 \n\t" \
);
#endif
/*
* Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
* the context save so we can write to the stack pointer.
*/
#if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__)
/* 3-Byte PC Restore */
#define portRESTORE_CONTEXT() \
__asm__ __volatile__ ( "lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"ld r28, x+ \n\t" \
"out __SP_L__, r28 \n\t" \
"ld r29, x+ \n\t" \
"out __SP_H__, r29 \n\t" \
"pop r31 \n\t" \
"pop r30 \n\t" \
"pop r29 \n\t" \
"pop r28 \n\t" \
"pop r27 \n\t" \
"pop r26 \n\t" \
"pop r25 \n\t" \
"pop r24 \n\t" \
"pop r23 \n\t" \
"pop r22 \n\t" \
"pop r21 \n\t" \
"pop r20 \n\t" \
"pop r19 \n\t" \
"pop r18 \n\t" \
"pop r17 \n\t" \
"pop r16 \n\t" \
"pop r15 \n\t" \
"pop r14 \n\t" \
"pop r13 \n\t" \
"pop r12 \n\t" \
"pop r11 \n\t" \
"pop r10 \n\t" \
"pop r9 \n\t" \
"pop r8 \n\t" \
"pop r7 \n\t" \
"pop r6 \n\t" \
"pop r5 \n\t" \
"pop r4 \n\t" \
"pop r3 \n\t" \
"pop r2 \n\t" \
"pop r1 \n\t" \
"pop r0 \n\t" \
"out 0x3c, r0 \n\t" \
"pop r0 \n\t" \
"out 0x3b, r0 \n\t" \
"pop r0 \n\t" \
"out __SREG__, r0 \n\t" \
"pop r0 \n\t" \
);
#else
/* 2-Byte PC Restore */
#define portRESTORE_CONTEXT() \
__asm__ __volatile__ ( "lds r26, pxCurrentTCB \n\t" \
"lds r27, pxCurrentTCB + 1 \n\t" \
"ld r28, x+ \n\t" \
"out __SP_L__, r28 \n\t" \
"ld r29, x+ \n\t" \
"out __SP_H__, r29 \n\t" \
"pop r31 \n\t" \
"pop r30 \n\t" \
"pop r29 \n\t" \
"pop r28 \n\t" \
"pop r27 \n\t" \
"pop r26 \n\t" \
"pop r25 \n\t" \
"pop r24 \n\t" \
"pop r23 \n\t" \
"pop r22 \n\t" \
"pop r21 \n\t" \
"pop r20 \n\t" \
"pop r19 \n\t" \
"pop r18 \n\t" \
"pop r17 \n\t" \
"pop r16 \n\t" \
"pop r15 \n\t" \
"pop r14 \n\t" \
"pop r13 \n\t" \
"pop r12 \n\t" \
"pop r11 \n\t" \
"pop r10 \n\t" \
"pop r9 \n\t" \
"pop r8 \n\t" \
"pop r7 \n\t" \
"pop r6 \n\t" \
"pop r5 \n\t" \
"pop r4 \n\t" \
"pop r3 \n\t" \
"pop r2 \n\t" \
"pop r1 \n\t" \
"pop r0 \n\t" \
"out __SREG__, r0 \n\t" \
"pop r0 \n\t" \
);
#endif
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
uint16_t usAddress;
#if defined (portQUAD_RAM) || defined (portMEGA_RAM)
// This function just here to ensure the library is included.
// Can go anywhere, as it is just to ensure that the .init3 code is included
extRAMcheck(); // This function just returns XMCRA. SRE is set if extended RAM enabled.
#warning "Ext RAM Enabled."
#endif
/* Place a few bytes of known values on the bottom of the stack.
This is just useful for debugging. */
*pxTopOfStack = 0x11;
pxTopOfStack--;
*pxTopOfStack = 0x22;
pxTopOfStack--;
*pxTopOfStack = 0x33;
pxTopOfStack--;
/* Simulate how the stack would look after a call to vPortYield() generated by
the compiler. */
/* The start of the task code will be popped off the stack last, so place
it on first. */
#if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__)
/* The AVR ATmega2560/ATmega2561 have 256KBytes of program memory and a 17-bit
* program counter. When a code address is stored on the stack, it takes 3 bytes
* instead of 2 for the other ATmega* chips.
*
* Store 0 as the top byte since we force all task routines to the bottom 128K
* of flash. We do this by using the .lowtext label in the linker script.
*
* In order to do this properly, we would need to get a full 3-byte pointer to
* pxCode. That requires a change to GCC. Not likely to happen any time soon.
*/
usAddress = ( uint16_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
*pxTopOfStack = 0;
pxTopOfStack--;
#else
usAddress = ( uint16_t ) pxCode;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
#endif
/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
portSAVE_CONTEXT places the flags on the stack immediately after r0
to ensure the interrupts get disabled as soon as possible, and so ensuring
the stack use is minimal should a context switch interrupt occur. */
*pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
pxTopOfStack--;
*pxTopOfStack = portFLAGS_INT_ENABLED;
pxTopOfStack--;
#if defined(__AVR_ATmega2560__) || defined(__AVR_ATmega2561__)
/* If we have an ATmega256x, we are also saving the RAMPZ and EIND registers.
* We should default those to 0.
*/
*pxTopOfStack = ( StackType_t ) 0x00; /* EIND */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x00; /* RAMPZ */
pxTopOfStack--;
#endif
/* Now the remaining registers. The compiler expects R1 to be 0. */
*pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x16; /* R16 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x17; /* R17 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
pxTopOfStack--;
/* Place the parameter on the stack in the expected location. */
usAddress = ( uint16_t ) pvParameters;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
usAddress >>= 8;
*pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x28; /* R28 Y */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x29; /* R29 */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
pxTopOfStack--;
*pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
pxTopOfStack--;
/*lint +e950 +e611 +e923 */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
BaseType_t xPortStartScheduler( void )
{
#if defined(DEBUG_PING)
DDRD |= _BV(DDD7); // set the debugging ping
PORTD &= ~_BV(PORTD7);
#endif
#if defined( portUSE_TIMER2_RTC ) && !defined( portUSE_TIMER2 )
/* Setup the timer hardware to generate the RTC sys_tick(), at 1 sec intervals. */
prvSetupRTCInterrupt();
#endif
/* Setup the relevant timer hardware to generate the tick. */
prvSetupTimerInterrupt();
/* Restore the context of the first task that is going to run. */
portRESTORE_CONTEXT();
/* Simulate a function call end as generated by the compiler. We will now
jump to the start of the task the context of which we have just restored. */
__asm__ __volatile__ ( "ret" );
/* Should not get here. */
return pdTRUE;
}
/*-----------------------------------------------------------*/
void vPortEndScheduler( void )
{
/* It is unlikely that the AVR port will get stopped. If required simply
disable the tick interrupt here. */
#if defined (portUSE_WDTO)
wdt_disable(); // disable Watchdog Timer
#elif defined( portUSE_TIMER0 )
portTIMSK &= ~( _BV(OCIE0B)|_BV(OCIE0A)|_BV(TOIE0) ); // disable all Timer0 interrupts
#elif defined( portUSE_TIMER1 )
portTIMSK &= ~( _BV(OCIE1B)|_BV(OCIE1A)|_BV(TOIE1) ); // disable all Timer1 interrupts
#elif defined( portUSE_TIMER2 )
portTIMSK &= ~( _BV(OCIE2B)|_BV(OCIE2A)|_BV(TOIE2) ); // disable all Timer2 interrupts
ASSR = 0x00; // set Timer/Counter2 to be off
#elif defined( portUSE_TIMER3 )
portTIMSK &= ~( _BV(OCIE3B)|_BV(OCIE3A)|_BV(TOIE3) ); // disable all Timer3 interrupts
#endif
}
/*-----------------------------------------------------------*/
/*
* Manual context switch. The first thing we do is save the registers so we
* can use a naked attribute.
*/
void vPortYield( void ) __attribute__ ( ( hot, flatten, naked ) );
void vPortYield( void )
{
portSAVE_CONTEXT();
vTaskSwitchContext();
portRESTORE_CONTEXT();
__asm__ __volatile__ ( "ret" );
}
/*-----------------------------------------------------------*/
/*
* Context switch function used by the tick. This must be identical to
* vPortYield() from the call to vTaskSwitchContext() onwards. The only
* difference from vPortYield() is the tick count is incremented as the
* call comes from the tick ISR.
*/
void vPortYieldFromTick( void ) __attribute__ ( ( hot, flatten, naked ) );
void vPortYieldFromTick( void )
{
portSAVE_CONTEXT();
sleep_reset(); // reset the sleep_mode() faster than sleep_disable();
#if defined(DEBUG_PING)
// start mark - check for start of interrupt - for debugging only
PORTD |= _BV(PORTD7); // Ping IO line.
#endif
#if !defined(portUSE_TIMER2_RTC)
if (--ticksRemainingInSec == 0)
{
//system_tick();
ticksRemainingInSec = portTickRateHz;
}
#endif
if( xTaskIncrementTick() != pdFALSE )
{
vTaskSwitchContext();
}
#if defined(DEBUG_PING)
// end mark - check for end of interrupt - for debugging only
PORTD &= ~_BV(PORTD7);
#endif
portRESTORE_CONTEXT();
__asm__ __volatile__ ( "ret" );
}
/*-----------------------------------------------------------*/
#if defined(portUSE_WDTO)
//initialize watchdog
void prvSetupTimerInterrupt( void )
{
//reset watchdog
wdt_reset();
/* actual port tick rate in Hz, calculated */
portTickRateHz = configTICK_RATE_HZ;
/* initialise first second of ticks */
ticksRemainingInSec = portTickRateHz;
//set up WDT Interrupt (rather than the WDT Reset).
wdt_interrupt_enable( portUSE_WDTO );
}
#elif defined (portUSE_TIMER0) || defined (portUSE_TIMER1) || defined (portUSE_TIMER3)
/*
* Setup timer 0 or 1 or 3 compare match A to generate a tick interrupt.
*/
static void prvSetupTimerInterrupt( void )
{
uint32_t ulCompareMatch;
#ifdef portOCRH
uint8_t ucHighByte;
#endif
uint8_t ucLowByte;
/* Using 8bit Timer0 or 16bit Timer1 or Timer3 to generate the tick. Correct fuses must be
selected for the configCPU_CLOCK_HZ clock.*/
// ulCompareMatch 40,000 = 20,000,000 / 500; 20MHz
// ulCompareMatch 110,592 = 22,118,400 / 200; 22.1184 MHz
ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
/* We only have 8 or 16 bits so have to scale 64 or 256 to get our required tick rate. */
//ulCompareMatch = 625 /= portCLOCK_PRESCALER; 20MHz with 64 prescale
//ulCompareMatch = 108 /= portCLOCK_PRESCALER; 22.1184 MHz with 1024 prescale
ulCompareMatch /= portCLOCK_PRESCALER;
/* actual port tick rate in Hz, calculated */
portTickRateHz = (TickType_t) ((uint32_t) configCPU_CLOCK_HZ / ( portCLOCK_PRESCALER * ulCompareMatch ));
/* initialise first second of ticks */
ticksRemainingInSec = portTickRateHz;
/* Adjust for correct value. */
ulCompareMatch -= ( uint32_t ) 1;
/* Setup compare match value for compare match A. Interrupts are disabled
before this is called so we need not worry here. */
ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
// OCR3AH = ucHighByte;
// OCR3AL = ucLowByte;
// the HiByte is only needed, if a 16 Bit counter is being utilized
#ifdef portOCRH
ulCompareMatch >>= 8;
ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t) 0xff );
portOCRH = ucHighByte;
#endif
portOCRL = ucLowByte;
#if defined( portUSE_TIMER0 )
/* Setup clock source and compare match behaviour. Assuming 328p (no Timer3) */
portTCCRa = portCLEAR_COUNTER_ON_MATCH;
portTCCRb = portPRESCALE_1024;
#elif defined( portUSE_TIMER1 )
/* Setup clock source and compare match behaviour. Assuming 328p (with Timer1) */
ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
portTCCRb = ucLowByte;
#elif defined( portUSE_TIMER3 )
/* Setup clock source and compare match behaviour. Assuming 640 / 1280 /1281 / 1284p / 2560 / 2561 (with Timer3) */
ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
portTCCRb = ucLowByte;
#endif
/* Enable the interrupt - this is okay as interrupt are currently globally disabled. */
ucLowByte = portTIMSK;
ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
portTIMSK = ucLowByte;
}
#endif
/*-----------------------------------------------------------*/
#if configUSE_PREEMPTION == 1
/*
* Tick ISR for preemptive scheduler. We can use a naked attribute as
* the context is saved at the start of vPortYieldFromTick(). The tick
* count is incremented after the context is saved.
*
* use ISR_NOBLOCK where there is an important timer running, that should preempt the scheduler.
*
*/
// ISR(portSCHEDULER_ISR, ISR_NAKED ISR_NOBLOCK)
ISR(portSCHEDULER_ISR, ISR_NAKED ISR_NOBLOCK) __attribute__ ((hot, flatten));
ISR(portSCHEDULER_ISR)
{
vPortYieldFromTick();
__asm__ __volatile__ ( "reti" );
}
#else
/*
* Tick ISR for the cooperative scheduler. All this does is increment the
* tick count. We don't need to switch context, this can only be done by
* manual calls to taskYIELD();
*
* use ISR_NOBLOCK where there is an important timer running, that should preempt the scheduler.
*/
// ISR(portSCHEDULER_ISR, ISR_NOBLOCK)
ISR(portSCHEDULER_ISR, ISR_NOBLOCK) __attribute__ ((hot, flatten));
ISR(portSCHEDULER_ISR)
{
#if !defined(portUSE_TIMER2_RTC)
if (--ticksRemainingInSec == 0)
{
ticksRemainingInSec = portTickRateHz;
}
#endif
xTaskIncrementTick();
}
#endif // configUSE_PREEMPTION