/* FreeRTOS V7.5.2 - Copyright (C) 2013 Real Time Engineers Ltd. VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION. *************************************************************************** * * * FreeRTOS provides completely free yet professionally developed, * * robust, strictly quality controlled, supported, and cross * * platform software that has become a de facto standard. * * * * Help yourself get started quickly and support the FreeRTOS * * project by purchasing a FreeRTOS tutorial book, reference * * manual, or both from: http://www.FreeRTOS.org/Documentation * * * * Thank you! * * * *************************************************************************** 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 from the following link: http://www.freertos.org/a00114.html 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, books, training, latest versions, license and Real Time Engineers Ltd. contact details. 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.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS licenses offer ticketed support, indemnification and 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! */ /*----------------------------------------------------------- * Implementation of functions defined in portable.h for the ARM CM0 port. *----------------------------------------------------------*/ /* Scheduler includes. */ #include "FreeRTOS.h" #include "task.h" /* Constants required to manipulate the NVIC. */ #define portNVIC_SYSTICK_CTRL ( ( volatile unsigned long *) 0xe000e010 ) #define portNVIC_SYSTICK_LOAD ( ( volatile unsigned long *) 0xe000e014 ) #define portNVIC_INT_CTRL ( ( volatile unsigned long *) 0xe000ed04 ) #define portNVIC_SYSPRI2 ( ( volatile unsigned long *) 0xe000ed20 ) #define portNVIC_SYSTICK_CLK 0x00000004 #define portNVIC_SYSTICK_INT 0x00000002 #define portNVIC_SYSTICK_ENABLE 0x00000001 #define portNVIC_PENDSVSET 0x10000000 #define portMIN_INTERRUPT_PRIORITY ( 255UL ) #define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL ) #define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL ) /* Constants required to set up the initial stack. */ #define portINITIAL_XPSR ( 0x01000000 ) /* Each task maintains its own interrupt status in the critical nesting variable. */ static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa; /* * Setup the timer to generate the tick interrupts. */ static void prvSetupTimerInterrupt( void ); /* * Exception handlers. */ void xPortPendSVHandler( void ) __attribute__ (( naked )); void xPortSysTickHandler( void ); void vPortSVCHandler( void ) __attribute__ (( naked )); /* * Start first task is a separate function so it can be tested in isolation. */ static void vPortStartFirstTask( void ) __attribute__ (( naked )); /*-----------------------------------------------------------*/ /* * See header file for description. */ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters ) { /* Simulate the stack frame as it would be created by a context switch interrupt. */ pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */ *pxTopOfStack = portINITIAL_XPSR; /* xPSR */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */ pxTopOfStack -= 6; /* LR, R12, R3..R1 */ *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */ pxTopOfStack -= 8; /* R11..R4. */ return pxTopOfStack; } /*-----------------------------------------------------------*/ void vPortSVCHandler( void ) { __asm volatile ( " ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */ " ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */ " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */ " add r0, r0, #16 \n" /* Move to the high registers. */ " ldmia r0!, {r4-r7} \n" /* Pop the high registers. */ " mov r8, r4 \n" " mov r9, r5 \n" " mov r10, r6 \n" " mov r11, r7 \n" " \n" " msr psp, r0 \n" /* Remember the new top of stack for the task. */ " \n" " sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */ " ldmia r0!, {r4-r7} \n" /* Pop low registers. */ " mov r1, r14 \n" /* OR R14 with 0x0d. */ " movs r0, #0x0d \n" " orr r1, r0 \n" " bx r1 \n" " \n" " .align 2 \n" "pxCurrentTCBConst2: .word pxCurrentTCB \n" ); } /*-----------------------------------------------------------*/ void vPortStartFirstTask( void ) { /* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector table offset register that can be used to locate the initial stack value. Not all M0 parts have the application vector table at address 0. */ __asm volatile( " cpsie i \n" /* Globally enable interrupts. */ " svc 0 \n" /* System call to start first task. */ " nop \n" ); } /*-----------------------------------------------------------*/ /* * See header file for description. */ portBASE_TYPE xPortStartScheduler( void ) { /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */ *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI; *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI; /* Start the timer that generates the tick ISR. Interrupts are disabled here already. */ prvSetupTimerInterrupt(); /* Initialise the critical nesting count ready for the first task. */ uxCriticalNesting = 0; /* Start the first task. */ vPortStartFirstTask(); /* Should not get here! */ return 0; } /*-----------------------------------------------------------*/ void vPortEndScheduler( void ) { /* It is unlikely that the CM0 port will require this function as there is nothing to return to. */ } /*-----------------------------------------------------------*/ void vPortYield( void ) { /* Set a PendSV to request a context switch. */ *( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET; /* Barriers are normally not required but do ensure the code is completely within the specified behaviour for the architecture. */ __asm volatile( "dsb" ); __asm volatile( "isb" ); } /*-----------------------------------------------------------*/ void vPortEnterCritical( void ) { portDISABLE_INTERRUPTS(); uxCriticalNesting++; __asm volatile( "dsb" ); __asm volatile( "isb" ); } /*-----------------------------------------------------------*/ void vPortExitCritical( void ) { uxCriticalNesting--; if( uxCriticalNesting == 0 ) { portENABLE_INTERRUPTS(); } } /*-----------------------------------------------------------*/ unsigned long ulSetInterruptMaskFromISR( void ) { __asm volatile( " mrs r0, PRIMASK \n" " cpsid i \n" " bx lr " ); /* To avoid compiler warnings. This line will never be reached. */ return 0; } /*-----------------------------------------------------------*/ void vClearInterruptMaskFromISR( unsigned long ulMask ) { __asm volatile( " msr PRIMASK, r0 \n" " bx lr " ); } /*-----------------------------------------------------------*/ void xPortPendSVHandler( void ) { /* This is a naked function. */ __asm volatile ( " mrs r0, psp \n" " \n" " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */ " ldr r2, [r3] \n" " \n" " sub r0, r0, #32 \n" /* Make space for the remaining low registers. */ " str r0, [r2] \n" /* Save the new top of stack. */ " stmia r0!, {r4-r7} \n" /* Store the low registers that are not saved automatically. */ " mov r4, r8 \n" /* Store the high registers. */ " mov r5, r9 \n" " mov r6, r10 \n" " mov r7, r11 \n" " stmia r0!, {r4-r7} \n" " \n" " push {r3, r14} \n" " cpsid i \n" " bl vTaskSwitchContext \n" " cpsie i \n" " pop {r2, r3} \n" /* lr goes in r3. r2 now holds tcb pointer. */ " \n" " ldr r1, [r2] \n" " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */ " add r0, r0, #16 \n" /* Move to the high registers. */ " ldmia r0!, {r4-r7} \n" /* Pop the high registers. */ " mov r8, r4 \n" " mov r9, r5 \n" " mov r10, r6 \n" " mov r11, r7 \n" " \n" " msr psp, r0 \n" /* Remember the new top of stack for the task. */ " \n" " sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */ " ldmia r0!, {r4-r7} \n" /* Pop low registers. */ " \n" " bx r3 \n" " \n" " .align 2 \n" "pxCurrentTCBConst: .word pxCurrentTCB " ); } /*-----------------------------------------------------------*/ void xPortSysTickHandler( void ) { unsigned long ulPreviousMask; ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR(); { /* Increment the RTOS tick. */ if( xTaskIncrementTick() != pdFALSE ) { /* Pend a context switch. */ *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET; } } portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask ); } /*-----------------------------------------------------------*/ /* * Setup the systick timer to generate the tick interrupts at the required * frequency. */ void prvSetupTimerInterrupt( void ) { /* Configure SysTick to interrupt at the requested rate. */ *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL; *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE; } /*-----------------------------------------------------------*/