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jeremybenn |
/*
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FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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***************************************************************************
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* *
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* If you are: *
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* *
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* + New to FreeRTOS, *
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* + Wanting to learn FreeRTOS or multitasking in general quickly *
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* + Looking for basic training, *
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* + Wanting to improve your FreeRTOS skills and productivity *
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* *
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* then take a look at the FreeRTOS books - available as PDF or paperback *
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* *
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* "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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* http://www.FreeRTOS.org/Documentation *
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* *
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* A pdf reference manual is also available. Both are usually delivered *
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* to your inbox within 20 minutes to two hours when purchased between 8am *
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* and 8pm GMT (although please allow up to 24 hours in case of *
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* exceptional circumstances). Thank you for your support! *
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* *
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***************************************************************************
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This file is part of the FreeRTOS distribution.
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FreeRTOS is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License (version 2) as published by the
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Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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***NOTE*** The exception to the GPL is included to allow you to distribute
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a combined work that includes FreeRTOS without being obliged to provide the
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source code for proprietary components outside of the FreeRTOS kernel.
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FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details. You should have received a copy of the GNU General Public
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License and the FreeRTOS license exception along with FreeRTOS; if not it
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can be viewed here: http://www.freertos.org/a00114.html and also obtained
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by writing to Richard Barry, contact details for whom are available on the
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FreeRTOS WEB site.
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1 tab == 4 spaces!
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http://www.FreeRTOS.org - Documentation, latest information, license and
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contact details.
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http://www.SafeRTOS.com - A version that is certified for use in safety
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critical systems.
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http://www.OpenRTOS.com - Commercial support, development, porting,
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licensing and training services.
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*/
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/*
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Changes from V2.6.0
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+ AVR port - Replaced the inb() and outb() functions with direct memory
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access. This allows the port to be built with the 20050414 build of
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WinAVR.
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*/
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#include <stdlib.h>
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#include <avr/interrupt.h>
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#include "FreeRTOS.h"
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#include "task.h"
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/*-----------------------------------------------------------
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* Implementation of functions defined in portable.h for the AVR port.
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*----------------------------------------------------------*/
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/* Start tasks with interrupts enables. */
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#define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x80 )
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/* Hardware constants for timer 1. */
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#define portCLEAR_COUNTER_ON_MATCH ( ( unsigned char ) 0x08 )
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#define portPRESCALE_64 ( ( unsigned char ) 0x03 )
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#define portCLOCK_PRESCALER ( ( unsigned long ) 64 )
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#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( unsigned char ) 0x10 )
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/*-----------------------------------------------------------*/
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/* We require the address of the pxCurrentTCB variable, but don't want to know
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any details of its type. */
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typedef void tskTCB;
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extern volatile tskTCB * volatile pxCurrentTCB;
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/*-----------------------------------------------------------*/
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/*
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* Macro to save all the general purpose registers, the save the stack pointer
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* into the TCB.
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*
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* The first thing we do is save the flags then disable interrupts. This is to
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* guard our stack against having a context switch interrupt after we have already
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* pushed the registers onto the stack - causing the 32 registers to be on the
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* stack twice.
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*
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* r1 is set to zero as the compiler expects it to be thus, however some
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* of the math routines make use of R1.
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*
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* The interrupts will have been disabled during the call to portSAVE_CONTEXT()
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* so we need not worry about reading/writing to the stack pointer.
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*/
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#define portSAVE_CONTEXT() \
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asm volatile ( "push r0 \n\t" \
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"in r0, __SREG__ \n\t" \
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"cli \n\t" \
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"push r0 \n\t" \
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"push r1 \n\t" \
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"clr r1 \n\t" \
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"push r2 \n\t" \
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"push r3 \n\t" \
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"push r4 \n\t" \
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"push r5 \n\t" \
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"push r6 \n\t" \
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"push r7 \n\t" \
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"push r8 \n\t" \
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"push r9 \n\t" \
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"push r10 \n\t" \
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"push r11 \n\t" \
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"push r12 \n\t" \
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"push r13 \n\t" \
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"push r14 \n\t" \
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"push r15 \n\t" \
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"push r16 \n\t" \
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"push r17 \n\t" \
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"push r18 \n\t" \
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"push r19 \n\t" \
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"push r20 \n\t" \
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"push r21 \n\t" \
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"push r22 \n\t" \
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"push r23 \n\t" \
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"push r24 \n\t" \
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"push r25 \n\t" \
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"push r26 \n\t" \
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"push r27 \n\t" \
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"push r28 \n\t" \
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"push r29 \n\t" \
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"push r30 \n\t" \
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"push r31 \n\t" \
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"lds r26, pxCurrentTCB \n\t" \
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"lds r27, pxCurrentTCB + 1 \n\t" \
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"in r0, 0x3d \n\t" \
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"st x+, r0 \n\t" \
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"in r0, 0x3e \n\t" \
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"st x+, r0 \n\t" \
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);
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/*
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* Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
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* the context save so we can write to the stack pointer.
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*/
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#define portRESTORE_CONTEXT() \
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asm volatile ( "lds r26, pxCurrentTCB \n\t" \
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"lds r27, pxCurrentTCB + 1 \n\t" \
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"ld r28, x+ \n\t" \
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"out __SP_L__, r28 \n\t" \
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"ld r29, x+ \n\t" \
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"out __SP_H__, r29 \n\t" \
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"pop r31 \n\t" \
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"pop r30 \n\t" \
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"pop r29 \n\t" \
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"pop r28 \n\t" \
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"pop r27 \n\t" \
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"pop r26 \n\t" \
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"pop r25 \n\t" \
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"pop r24 \n\t" \
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"pop r23 \n\t" \
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"pop r22 \n\t" \
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"pop r21 \n\t" \
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"pop r20 \n\t" \
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"pop r19 \n\t" \
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"pop r18 \n\t" \
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"pop r17 \n\t" \
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"pop r16 \n\t" \
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"pop r15 \n\t" \
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"pop r14 \n\t" \
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"pop r13 \n\t" \
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"pop r12 \n\t" \
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"pop r11 \n\t" \
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"pop r10 \n\t" \
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"pop r9 \n\t" \
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"pop r8 \n\t" \
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"pop r7 \n\t" \
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"pop r6 \n\t" \
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"pop r5 \n\t" \
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"pop r4 \n\t" \
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"pop r3 \n\t" \
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"pop r2 \n\t" \
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"pop r1 \n\t" \
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"pop r0 \n\t" \
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"out __SREG__, r0 \n\t" \
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"pop r0 \n\t" \
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);
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/*-----------------------------------------------------------*/
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/*
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* Perform hardware setup to enable ticks from timer 1, compare match A.
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*/
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static void prvSetupTimerInterrupt( void );
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/*-----------------------------------------------------------*/
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/*
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* See header file for description.
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*/
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portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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{
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unsigned short usAddress;
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/* Place a few bytes of known values on the bottom of the stack.
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This is just useful for debugging. */
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*pxTopOfStack = 0x11;
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pxTopOfStack--;
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*pxTopOfStack = 0x22;
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pxTopOfStack--;
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*pxTopOfStack = 0x33;
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pxTopOfStack--;
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/* Simulate how the stack would look after a call to vPortYield() generated by
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the compiler. */
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/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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/* The start of the task code will be popped off the stack last, so place
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it on first. */
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usAddress = ( unsigned short ) pxCode;
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*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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pxTopOfStack--;
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usAddress >>= 8;
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*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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pxTopOfStack--;
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/* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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portSAVE_CONTEXT places the flags on the stack immediately after r0
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to ensure the interrupts get disabled as soon as possible, and so ensuring
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the stack use is minimal should a context switch interrupt occur. */
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*pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R0 */
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pxTopOfStack--;
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*pxTopOfStack = portFLAGS_INT_ENABLED;
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pxTopOfStack--;
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/* Now the remaining registers. The compiler expects R1 to be 0. */
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*pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R1 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x02; /* R2 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x03; /* R3 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x04; /* R4 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x05; /* R5 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x06; /* R6 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x07; /* R7 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x08; /* R8 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x09; /* R9 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x10; /* R10 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* R11 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x12; /* R12 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x13; /* R13 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x14; /* R14 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x15; /* R15 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x16; /* R16 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x17; /* R17 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x18; /* R18 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x19; /* R19 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x20; /* R20 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x21; /* R21 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* R22 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x23; /* R23 */
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pxTopOfStack--;
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/* Place the parameter on the stack in the expected location. */
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usAddress = ( unsigned short ) pvParameters;
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*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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pxTopOfStack--;
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usAddress >>= 8;
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*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x26; /* R26 X */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x27; /* R27 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x28; /* R28 Y */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x29; /* R29 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x30; /* R30 Z */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x031; /* R31 */
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pxTopOfStack--;
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/*lint +e950 +e611 +e923 */
|
| 321 |
|
|
|
| 322 |
|
|
return pxTopOfStack;
|
| 323 |
|
|
}
|
| 324 |
|
|
/*-----------------------------------------------------------*/
|
| 325 |
|
|
|
| 326 |
|
|
portBASE_TYPE xPortStartScheduler( void )
|
| 327 |
|
|
{
|
| 328 |
|
|
/* Setup the hardware to generate the tick. */
|
| 329 |
|
|
prvSetupTimerInterrupt();
|
| 330 |
|
|
|
| 331 |
|
|
/* Restore the context of the first task that is going to run. */
|
| 332 |
|
|
portRESTORE_CONTEXT();
|
| 333 |
|
|
|
| 334 |
|
|
/* Simulate a function call end as generated by the compiler. We will now
|
| 335 |
|
|
jump to the start of the task the context of which we have just restored. */
|
| 336 |
|
|
asm volatile ( "ret" );
|
| 337 |
|
|
|
| 338 |
|
|
/* Should not get here. */
|
| 339 |
|
|
return pdTRUE;
|
| 340 |
|
|
}
|
| 341 |
|
|
/*-----------------------------------------------------------*/
|
| 342 |
|
|
|
| 343 |
|
|
void vPortEndScheduler( void )
|
| 344 |
|
|
{
|
| 345 |
|
|
/* It is unlikely that the AVR port will get stopped. If required simply
|
| 346 |
|
|
disable the tick interrupt here. */
|
| 347 |
|
|
}
|
| 348 |
|
|
/*-----------------------------------------------------------*/
|
| 349 |
|
|
|
| 350 |
|
|
/*
|
| 351 |
|
|
* Manual context switch. The first thing we do is save the registers so we
|
| 352 |
|
|
* can use a naked attribute.
|
| 353 |
|
|
*/
|
| 354 |
|
|
void vPortYield( void ) __attribute__ ( ( naked ) );
|
| 355 |
|
|
void vPortYield( void )
|
| 356 |
|
|
{
|
| 357 |
|
|
portSAVE_CONTEXT();
|
| 358 |
|
|
vTaskSwitchContext();
|
| 359 |
|
|
portRESTORE_CONTEXT();
|
| 360 |
|
|
|
| 361 |
|
|
asm volatile ( "ret" );
|
| 362 |
|
|
}
|
| 363 |
|
|
/*-----------------------------------------------------------*/
|
| 364 |
|
|
|
| 365 |
|
|
/*
|
| 366 |
|
|
* Context switch function used by the tick. This must be identical to
|
| 367 |
|
|
* vPortYield() from the call to vTaskSwitchContext() onwards. The only
|
| 368 |
|
|
* difference from vPortYield() is the tick count is incremented as the
|
| 369 |
|
|
* call comes from the tick ISR.
|
| 370 |
|
|
*/
|
| 371 |
|
|
void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
|
| 372 |
|
|
void vPortYieldFromTick( void )
|
| 373 |
|
|
{
|
| 374 |
|
|
portSAVE_CONTEXT();
|
| 375 |
|
|
vTaskIncrementTick();
|
| 376 |
|
|
vTaskSwitchContext();
|
| 377 |
|
|
portRESTORE_CONTEXT();
|
| 378 |
|
|
|
| 379 |
|
|
asm volatile ( "ret" );
|
| 380 |
|
|
}
|
| 381 |
|
|
/*-----------------------------------------------------------*/
|
| 382 |
|
|
|
| 383 |
|
|
/*
|
| 384 |
|
|
* Setup timer 1 compare match A to generate a tick interrupt.
|
| 385 |
|
|
*/
|
| 386 |
|
|
static void prvSetupTimerInterrupt( void )
|
| 387 |
|
|
{
|
| 388 |
|
|
unsigned long ulCompareMatch;
|
| 389 |
|
|
unsigned char ucHighByte, ucLowByte;
|
| 390 |
|
|
|
| 391 |
|
|
/* Using 16bit timer 1 to generate the tick. Correct fuses must be
|
| 392 |
|
|
selected for the configCPU_CLOCK_HZ clock. */
|
| 393 |
|
|
|
| 394 |
|
|
ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
|
| 395 |
|
|
|
| 396 |
|
|
/* We only have 16 bits so have to scale to get our required tick rate. */
|
| 397 |
|
|
ulCompareMatch /= portCLOCK_PRESCALER;
|
| 398 |
|
|
|
| 399 |
|
|
/* Adjust for correct value. */
|
| 400 |
|
|
ulCompareMatch -= ( unsigned long ) 1;
|
| 401 |
|
|
|
| 402 |
|
|
/* Setup compare match value for compare match A. Interrupts are disabled
|
| 403 |
|
|
before this is called so we need not worry here. */
|
| 404 |
|
|
ucLowByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
|
| 405 |
|
|
ulCompareMatch >>= 8;
|
| 406 |
|
|
ucHighByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
|
| 407 |
|
|
OCR1AH = ucHighByte;
|
| 408 |
|
|
OCR1AL = ucLowByte;
|
| 409 |
|
|
|
| 410 |
|
|
/* Setup clock source and compare match behaviour. */
|
| 411 |
|
|
ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
|
| 412 |
|
|
TCCR1B = ucLowByte;
|
| 413 |
|
|
|
| 414 |
|
|
/* Enable the interrupt - this is okay as interrupt are currently globally
|
| 415 |
|
|
disabled. */
|
| 416 |
|
|
ucLowByte = TIMSK;
|
| 417 |
|
|
ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
|
| 418 |
|
|
TIMSK = ucLowByte;
|
| 419 |
|
|
}
|
| 420 |
|
|
/*-----------------------------------------------------------*/
|
| 421 |
|
|
|
| 422 |
|
|
#if configUSE_PREEMPTION == 1
|
| 423 |
|
|
|
| 424 |
|
|
/*
|
| 425 |
|
|
* Tick ISR for preemptive scheduler. We can use a naked attribute as
|
| 426 |
|
|
* the context is saved at the start of vPortYieldFromTick(). The tick
|
| 427 |
|
|
* count is incremented after the context is saved.
|
| 428 |
|
|
*/
|
| 429 |
|
|
void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
|
| 430 |
|
|
void SIG_OUTPUT_COMPARE1A( void )
|
| 431 |
|
|
{
|
| 432 |
|
|
vPortYieldFromTick();
|
| 433 |
|
|
asm volatile ( "reti" );
|
| 434 |
|
|
}
|
| 435 |
|
|
#else
|
| 436 |
|
|
|
| 437 |
|
|
/*
|
| 438 |
|
|
* Tick ISR for the cooperative scheduler. All this does is increment the
|
| 439 |
|
|
* tick count. We don't need to switch context, this can only be done by
|
| 440 |
|
|
* manual calls to taskYIELD();
|
| 441 |
|
|
*/
|
| 442 |
|
|
void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
|
| 443 |
|
|
void SIG_OUTPUT_COMPARE1A( void )
|
| 444 |
|
|
{
|
| 445 |
|
|
vTaskIncrementTick();
|
| 446 |
|
|
}
|
| 447 |
|
|
#endif
|
| 448 |
|
|
|
| 449 |
|
|
|
| 450 |
|
|
|
