diff options
Diffstat (limited to 'FreeRTOS/Source/portable/MPLAB/PIC18F/port.c')
| -rw-r--r-- | FreeRTOS/Source/portable/MPLAB/PIC18F/port.c | 657 |
1 files changed, 657 insertions, 0 deletions
diff --git a/FreeRTOS/Source/portable/MPLAB/PIC18F/port.c b/FreeRTOS/Source/portable/MPLAB/PIC18F/port.c new file mode 100644 index 000000000..3d91b955b --- /dev/null +++ b/FreeRTOS/Source/portable/MPLAB/PIC18F/port.c @@ -0,0 +1,657 @@ +/*
+ FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
+
+
+ ***************************************************************************
+ * *
+ * FreeRTOS tutorial books are available in pdf and paperback. *
+ * Complete, revised, and edited pdf reference manuals are also *
+ * available. *
+ * *
+ * Purchasing FreeRTOS documentation will not only help you, by *
+ * ensuring you get running as quickly as possible and with an *
+ * in-depth knowledge of how to use FreeRTOS, it will also help *
+ * the FreeRTOS project to continue with its mission of providing *
+ * professional grade, cross platform, de facto standard solutions *
+ * for microcontrollers - completely free of charge! *
+ * *
+ * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
+ * *
+ * Thank you for using FreeRTOS, and thank you for your support! *
+ * *
+ ***************************************************************************
+
+
+ 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. See the GNU General Public License for
+ more details. You should have received a copy of the GNU General Public
+ License and the FreeRTOS license exception along with FreeRTOS; if not it
+ can be viewed here: http://www.freertos.org/a00114.html and also obtained
+ by writing to Richard Barry, contact details for whom are available on the
+ FreeRTOS WEB site.
+
+ 1 tab == 4 spaces!
+
+ ***************************************************************************
+ * *
+ * Having a problem? Start by reading the FAQ "My application does *
+ * not run, what could be wrong? *
+ * *
+ * http://www.FreeRTOS.org/FAQHelp.html *
+ * *
+ ***************************************************************************
+
+
+ http://www.FreeRTOS.org - Documentation, training, latest information,
+ license and contact details.
+
+ http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
+ including FreeRTOS+Trace - an indispensable productivity tool.
+
+ Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
+ the code with commercial support, indemnification, and middleware, under
+ the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
+ provide a safety engineered and independently SIL3 certified version under
+ the SafeRTOS brand: http://www.SafeRTOS.com.
+*/
+
+/*
+Changes between V1.2.4 and V1.2.5
+
+ + Introduced portGLOBAL_INTERRUPT_FLAG definition to test the global
+ interrupt flag setting. Using the two bits defined within
+ portINITAL_INTERRUPT_STATE was causing the w register to get clobbered
+ before the test was performed.
+
+Changes from V1.2.5
+
+ + Set the interrupt vector address to 0x08. Previously it was at the
+ incorrect address for compatibility mode of 0x18.
+
+Changes from V2.1.1
+
+ + PCLATU and PCLATH are now saved as part of the context. This allows
+ function pointers to be used within tasks. Thanks to Javier Espeche
+ for the enhancement.
+
+Changes from V2.3.1
+
+ + TABLAT is now saved as part of the task context.
+
+Changes from V3.2.0
+
+ + TBLPTRU is now initialised to zero as the MPLAB compiler expects this
+ value and does not write to the register.
+*/
+
+/* Scheduler include files. */
+#include "FreeRTOS.h"
+#include "task.h"
+
+/* MPLAB library include file. */
+#include "timers.h"
+
+/*-----------------------------------------------------------
+ * Implementation of functions defined in portable.h for the PIC port.
+ *----------------------------------------------------------*/
+
+/* Hardware setup for tick. */
+#define portTIMER_FOSC_SCALE ( ( unsigned long ) 4 )
+
+/* Initial interrupt enable state for newly created tasks. This value is
+copied into INTCON when a task switches in for the first time. */
+#define portINITAL_INTERRUPT_STATE 0xc0
+
+/* Just the bit within INTCON for the global interrupt flag. */
+#define portGLOBAL_INTERRUPT_FLAG 0x80
+
+/* Constant used for context switch macro when we require the interrupt
+enable state to be unchanged when the interrupted task is switched back in. */
+#define portINTERRUPTS_UNCHANGED 0x00
+
+/* Some memory areas get saved as part of the task context. These memory
+area's get used by the compiler for temporary storage, especially when
+performing mathematical operations, or when using 32bit data types. This
+constant defines the size of memory area which must be saved. */
+#define portCOMPILER_MANAGED_MEMORY_SIZE ( ( unsigned char ) 0x13 )
+
+/* We require the address of the pxCurrentTCB variable, but don't want to know
+any details of its type. */
+typedef void tskTCB;
+extern volatile tskTCB * volatile pxCurrentTCB;
+
+/* IO port constants. */
+#define portBIT_SET ( ( unsigned char ) 1 )
+#define portBIT_CLEAR ( ( unsigned char ) 0 )
+
+/*
+ * The serial port ISR's are defined in serial.c, but are called from portable
+ * as they use the same vector as the tick ISR.
+ */
+void vSerialTxISR( void );
+void vSerialRxISR( void );
+
+/*
+ * Perform hardware setup to enable ticks.
+ */
+static void prvSetupTimerInterrupt( void );
+
+/*
+ * ISR to maintain the tick, and perform tick context switches if the
+ * preemptive scheduler is being used.
+ */
+static void prvTickISR( void );
+
+/*
+ * ISR placed on the low priority vector. This calls the appropriate ISR for
+ * the actual interrupt.
+ */
+static void prvLowInterrupt( void );
+
+/*
+ * Macro that pushes all the registers that make up the context of a task onto
+ * the stack, then saves the new top of stack into the TCB.
+ *
+ * If this is called from an ISR then the interrupt enable bits must have been
+ * set for the ISR to ever get called. Therefore we want to save the INTCON
+ * register with the enable bits forced to be set - and ucForcedInterruptFlags
+ * must contain these bit settings. This means the interrupts will again be
+ * enabled when the interrupted task is switched back in.
+ *
+ * If this is called from a manual context switch (i.e. from a call to yield),
+ * then we want to save the INTCON so it is restored with its current state,
+ * and ucForcedInterruptFlags must be 0. This allows a yield from within
+ * a critical section.
+ *
+ * The compiler uses some locations at the bottom of the memory for temporary
+ * storage during math and other computations. This is especially true if
+ * 32bit data types are utilised (as they are by the scheduler). The .tmpdata
+ * and MATH_DATA sections have to be stored in there entirety as part of a task
+ * context. This macro stores from data address 0x00 to
+ * portCOMPILER_MANAGED_MEMORY_SIZE. This is sufficient for the demo
+ * applications but you should check the map file for your project to ensure
+ * this is sufficient for your needs. It is not clear whether this size is
+ * fixed for all compilations or has the potential to be program specific.
+ */
+#define portSAVE_CONTEXT( ucForcedInterruptFlags ) \
+{ \
+ _asm \
+ /* Save the status and WREG registers first, as these will get modified \
+ by the operations below. */ \
+ MOVFF WREG, PREINC1 \
+ MOVFF STATUS, PREINC1 \
+ /* Save the INTCON register with the appropriate bits forced if \
+ necessary - as described above. */ \
+ MOVFF INTCON, WREG \
+ IORLW ucForcedInterruptFlags \
+ MOVFF WREG, PREINC1 \
+ _endasm \
+ \
+ portDISABLE_INTERRUPTS(); \
+ \
+ _asm \
+ /* Store the necessary registers to the stack. */ \
+ MOVFF BSR, PREINC1 \
+ MOVFF FSR2L, PREINC1 \
+ MOVFF FSR2H, PREINC1 \
+ MOVFF FSR0L, PREINC1 \
+ MOVFF FSR0H, PREINC1 \
+ MOVFF TABLAT, PREINC1 \
+ MOVFF TBLPTRU, PREINC1 \
+ MOVFF TBLPTRH, PREINC1 \
+ MOVFF TBLPTRL, PREINC1 \
+ MOVFF PRODH, PREINC1 \
+ MOVFF PRODL, PREINC1 \
+ MOVFF PCLATU, PREINC1 \
+ MOVFF PCLATH, PREINC1 \
+ /* Store the .tempdata and MATH_DATA areas as described above. */ \
+ CLRF FSR0L, 0 \
+ CLRF FSR0H, 0 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF POSTINC0, PREINC1 \
+ MOVFF INDF0, PREINC1 \
+ MOVFF FSR0L, PREINC1 \
+ MOVFF FSR0H, PREINC1 \
+ /* Store the hardware stack pointer in a temp register before we \
+ modify it. */ \
+ MOVFF STKPTR, FSR0L \
+ _endasm \
+ \
+ /* Store each address from the hardware stack. */ \
+ while( STKPTR > ( unsigned char ) 0 ) \
+ { \
+ _asm \
+ MOVFF TOSL, PREINC1 \
+ MOVFF TOSH, PREINC1 \
+ MOVFF TOSU, PREINC1 \
+ POP \
+ _endasm \
+ } \
+ \
+ _asm \
+ /* Store the number of addresses on the hardware stack (from the \
+ temporary register). */ \
+ MOVFF FSR0L, PREINC1 \
+ MOVF PREINC1, 1, 0 \
+ _endasm \
+ \
+ /* Save the new top of the software stack in the TCB. */ \
+ _asm \
+ MOVFF pxCurrentTCB, FSR0L \
+ MOVFF pxCurrentTCB + 1, FSR0H \
+ MOVFF FSR1L, POSTINC0 \
+ MOVFF FSR1H, POSTINC0 \
+ _endasm \
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * This is the reverse of portSAVE_CONTEXT. See portSAVE_CONTEXT for more
+ * details.
+ */
+#define portRESTORE_CONTEXT() \
+{ \
+ _asm \
+ /* Set FSR0 to point to pxCurrentTCB->pxTopOfStack. */ \
+ MOVFF pxCurrentTCB, FSR0L \
+ MOVFF pxCurrentTCB + 1, FSR0H \
+ \
+ /* De-reference FSR0 to set the address it holds into FSR1. \
+ (i.e. *( pxCurrentTCB->pxTopOfStack ) ). */ \
+ MOVFF POSTINC0, FSR1L \
+ MOVFF POSTINC0, FSR1H \
+ \
+ /* How many return addresses are there on the hardware stack? Discard \
+ the first byte as we are pointing to the next free space. */ \
+ MOVFF POSTDEC1, FSR0L \
+ MOVFF POSTDEC1, FSR0L \
+ _endasm \
+ \
+ /* Fill the hardware stack from our software stack. */ \
+ STKPTR = 0; \
+ \
+ while( STKPTR < FSR0L ) \
+ { \
+ _asm \
+ PUSH \
+ MOVF POSTDEC1, 0, 0 \
+ MOVWF TOSU, 0 \
+ MOVF POSTDEC1, 0, 0 \
+ MOVWF TOSH, 0 \
+ MOVF POSTDEC1, 0, 0 \
+ MOVWF TOSL, 0 \
+ _endasm \
+ } \
+ \
+ _asm \
+ /* Restore the .tmpdata and MATH_DATA memory. */ \
+ MOVFF POSTDEC1, FSR0H \
+ MOVFF POSTDEC1, FSR0L \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, POSTDEC0 \
+ MOVFF POSTDEC1, INDF0 \
+ /* Restore the other registers forming the tasks context. */ \
+ MOVFF POSTDEC1, PCLATH \
+ MOVFF POSTDEC1, PCLATU \
+ MOVFF POSTDEC1, PRODL \
+ MOVFF POSTDEC1, PRODH \
+ MOVFF POSTDEC1, TBLPTRL \
+ MOVFF POSTDEC1, TBLPTRH \
+ MOVFF POSTDEC1, TBLPTRU \
+ MOVFF POSTDEC1, TABLAT \
+ MOVFF POSTDEC1, FSR0H \
+ MOVFF POSTDEC1, FSR0L \
+ MOVFF POSTDEC1, FSR2H \
+ MOVFF POSTDEC1, FSR2L \
+ MOVFF POSTDEC1, BSR \
+ /* The next byte is the INTCON register. Read this into WREG as some \
+ manipulation is required. */ \
+ MOVFF POSTDEC1, WREG \
+ _endasm \
+ \
+ /* From the INTCON register, only the interrupt enable bits form part \
+ of the tasks context. It is perfectly legitimate for another task to \
+ have modified any other bits. We therefore only restore the top two bits. \
+ */ \
+ if( WREG & portGLOBAL_INTERRUPT_FLAG ) \
+ { \
+ _asm \
+ MOVFF POSTDEC1, STATUS \
+ MOVFF POSTDEC1, WREG \
+ /* Return enabling interrupts. */ \
+ RETFIE 0 \
+ _endasm \
+ } \
+ else \
+ { \
+ _asm \
+ MOVFF POSTDEC1, STATUS \
+ MOVFF POSTDEC1, WREG \
+ /* Return without effecting interrupts. The context may have \
+ been saved from a critical region. */ \
+ RETURN 0 \
+ _endasm \
+ } \
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * See header file for description.
+ */
+portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
+{
+unsigned long ulAddress;
+unsigned char ucBlock;
+
+ /* 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.
+
+ First store the function parameters. This is where the task will expect to
+ find them when it starts running. */
+ ulAddress = ( unsigned long ) pvParameters;
+ *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress & ( unsigned long ) 0x00ff );
+ pxTopOfStack++;
+
+ ulAddress >>= 8;
+ *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress & ( unsigned long ) 0x00ff );
+ pxTopOfStack++;
+
+ /* Next we just leave a space. When a context is saved the stack pointer
+ is incremented before it is used so as not to corrupt whatever the stack
+ pointer is actually pointing to. This is especially necessary during
+ function epilogue code generated by the compiler. */
+ *pxTopOfStack = 0x44;
+ pxTopOfStack++;
+
+ /* Next are all the registers that form part of the task context. */
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x66; /* WREG. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0xcc; /* Status. */
+ pxTopOfStack++;
+
+ /* INTCON is saved with interrupts enabled. */
+ *pxTopOfStack = ( portSTACK_TYPE ) portINITAL_INTERRUPT_STATE; /* INTCON */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* BSR. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* FSR2L. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x33; /* FSR2H. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x44; /* FSR0L. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x55; /* FSR0H. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x66; /* TABLAT. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* TBLPTRU. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x88; /* TBLPTRUH. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x99; /* TBLPTRUL. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0xaa; /* PRODH. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0xbb; /* PRODL. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* PCLATU. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* PCLATH. */
+ pxTopOfStack++;
+
+ /* Next the .tmpdata and MATH_DATA sections. */
+ for( ucBlock = 0; ucBlock <= portCOMPILER_MANAGED_MEMORY_SIZE; ucBlock++ )
+ {
+ *pxTopOfStack = ( portSTACK_TYPE ) ucBlock;
+ *pxTopOfStack++;
+ }
+
+ /* Store the top of the global data section. */
+ *pxTopOfStack = ( portSTACK_TYPE ) portCOMPILER_MANAGED_MEMORY_SIZE; /* Low. */
+ pxTopOfStack++;
+
+ *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* High. */
+ pxTopOfStack++;
+
+ /* The only function return address so far is the address of the
+ task. */
+ ulAddress = ( unsigned long ) pxCode;
+
+ /* TOS low. */
+ *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress & ( unsigned long ) 0x00ff );
+ pxTopOfStack++;
+ ulAddress >>= 8;
+
+ /* TOS high. */
+ *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress & ( unsigned long ) 0x00ff );
+ pxTopOfStack++;
+ ulAddress >>= 8;
+
+ /* TOS even higher. */
+ *pxTopOfStack = ( portSTACK_TYPE ) ( ulAddress & ( unsigned long ) 0x00ff );
+ pxTopOfStack++;
+
+ /* Store the number of return addresses on the hardware stack - so far only
+ the address of the task entry point. */
+ *pxTopOfStack = ( portSTACK_TYPE ) 1;
+ pxTopOfStack++;
+
+ return pxTopOfStack;
+}
+/*-----------------------------------------------------------*/
+
+portBASE_TYPE xPortStartScheduler( void )
+{
+ /* Setup a timer for the tick ISR is using the preemptive scheduler. */
+ prvSetupTimerInterrupt();
+
+ /* Restore the context of the first task to run. */
+ portRESTORE_CONTEXT();
+
+ /* Should not get here. Use the function name to stop compiler warnings. */
+ ( void ) prvLowInterrupt;
+ ( void ) prvTickISR;
+
+ return pdTRUE;
+}
+/*-----------------------------------------------------------*/
+
+void vPortEndScheduler( void )
+{
+ /* It is unlikely that the scheduler for the PIC port will get stopped
+ once running. If required disable the tick interrupt here, then return
+ to xPortStartScheduler(). */
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Manual context switch. This is similar to the tick context switch,
+ * but does not increment the tick count. It must be identical to the
+ * tick context switch in how it stores the stack of a task.
+ */
+void vPortYield( void )
+{
+ /* This can get called with interrupts either enabled or disabled. We
+ will save the INTCON register with the interrupt enable bits unmodified. */
+ portSAVE_CONTEXT( portINTERRUPTS_UNCHANGED );
+
+ /* Switch to the highest priority task that is ready to run. */
+ vTaskSwitchContext();
+
+ /* Start executing the task we have just switched to. */
+ portRESTORE_CONTEXT();
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Vector for ISR. Nothing here must alter any registers!
+ */
+#pragma code high_vector=0x08
+static void prvLowInterrupt( void )
+{
+ /* Was the interrupt the tick? */
+ if( PIR1bits.CCP1IF )
+ {
+ _asm
+ goto prvTickISR
+ _endasm
+ }
+
+ /* Was the interrupt a byte being received? */
+ if( PIR1bits.RCIF )
+ {
+ _asm
+ goto vSerialRxISR
+ _endasm
+ }
+
+ /* Was the interrupt the Tx register becoming empty? */
+ if( PIR1bits.TXIF )
+ {
+ if( PIE1bits.TXIE )
+ {
+ _asm
+ goto vSerialTxISR
+ _endasm
+ }
+ }
+}
+#pragma code
+
+/*-----------------------------------------------------------*/
+
+/*
+ * ISR for the tick.
+ * This increments the tick count and, if using the preemptive scheduler,
+ * performs a context switch. This must be identical to the manual
+ * context switch in how it stores the context of a task.
+ */
+static void prvTickISR( void )
+{
+ /* Interrupts must have been enabled for the ISR to fire, so we have to
+ save the context with interrupts enabled. */
+ portSAVE_CONTEXT( portGLOBAL_INTERRUPT_FLAG );
+ PIR1bits.CCP1IF = 0;
+
+ /* Maintain the tick count. */
+ vTaskIncrementTick();
+
+ #if configUSE_PREEMPTION == 1
+ {
+ /* Switch to the highest priority task that is ready to run. */
+ vTaskSwitchContext();
+ }
+ #endif
+
+ portRESTORE_CONTEXT();
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Setup a timer for a regular tick.
+ */
+static void prvSetupTimerInterrupt( void )
+{
+const unsigned long ulConstCompareValue = ( ( configCPU_CLOCK_HZ / portTIMER_FOSC_SCALE ) / configTICK_RATE_HZ );
+unsigned long ulCompareValue;
+unsigned char ucByte;
+
+ /* Interrupts are disabled when this function is called.
+
+ Setup CCP1 to provide the tick interrupt using a compare match on timer
+ 1.
+
+ Clear the time count then setup timer. */
+ TMR1H = ( unsigned char ) 0x00;
+ TMR1L = ( unsigned char ) 0x00;
+
+ /* Set the compare match value. */
+ ulCompareValue = ulConstCompareValue;
+ CCPR1L = ( unsigned char ) ( ulCompareValue & ( unsigned long ) 0xff );
+ ulCompareValue >>= ( unsigned long ) 8;
+ CCPR1H = ( unsigned char ) ( ulCompareValue & ( unsigned long ) 0xff );
+
+ CCP1CONbits.CCP1M0 = portBIT_SET; /*< Compare match mode. */
+ CCP1CONbits.CCP1M1 = portBIT_SET; /*< Compare match mode. */
+ CCP1CONbits.CCP1M2 = portBIT_CLEAR; /*< Compare match mode. */
+ CCP1CONbits.CCP1M3 = portBIT_SET; /*< Compare match mode. */
+ PIE1bits.CCP1IE = portBIT_SET; /*< Interrupt enable. */
+
+ /* We are only going to use the global interrupt bit, so set the peripheral
+ bit to true. */
+ INTCONbits.GIEL = portBIT_SET;
+
+ /* Provided library function for setting up the timer that will produce the
+ tick. */
+ OpenTimer1( T1_16BIT_RW & T1_SOURCE_INT & T1_PS_1_1 & T1_CCP1_T3_CCP2 );
+}
+
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