text: /*
   * FreeRTOS Kernel V10.3.0
   * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   * http://www.FreeRTOS.org
   * http://aws.amazon.com/freertos
   *
   * 1 tab == 4 spaces!
   */
  
  /*-----------------------------------------------------------
   * Implementation of functions defined in portable.h for the ST STR75x ARM7
   * port.
   *----------------------------------------------------------*/
  
  /* Library includes. */
  #include "75x_tb.h"
  #include "75x_eic.h"
  
  /* Scheduler includes. */
  #include "FreeRTOS.h"
  #include "task.h"
  
  /* Constants required to setup the initial stack. */
  #define portINITIAL_SPSR				( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
  #define portTHUMB_MODE_BIT				( ( StackType_t ) 0x20 )
  #define portINSTRUCTION_SIZE			( ( StackType_t ) 4 )
  
  /* Constants required to handle critical sections. */
  #define portNO_CRITICAL_NESTING 		( ( uint32_t ) 0 )
  
  /* Prescale used on the timer clock when calculating the tick period. */
  #define portPRESCALE 20
  
  
  /*-----------------------------------------------------------*/
  
  /* Setup the TB to generate the tick interrupts. */
  static void prvSetupTimerInterrupt( void );
  
  /*-----------------------------------------------------------*/
  
  /*
   * Initialise the stack of a task to look exactly as if a call to
   * portSAVE_CONTEXT had been called.
   *
   * See header file for description.
   */
  StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
  {
  StackType_t *pxOriginalTOS;
  
  	pxOriginalTOS = pxTopOfStack;
  
  	/* To ensure asserts in tasks.c don't fail, although in this case the assert
  	is not really required. */
  	pxTopOfStack--;
  
  	/* Setup the initial stack of the task.  The stack is set exactly as
  	expected by the portRESTORE_CONTEXT() macro. */
  
  	/* First on the stack is the return address - which in this case is the
  	start of the task.  The offset is added to make the return address appear
  	as it would within an IRQ ISR. */
  	*pxTopOfStack = ( StackType_t ) pxCode + portINSTRUCTION_SIZE;		
  	pxTopOfStack--;
  
  	*pxTopOfStack = ( StackType_t ) 0xaaaaaaaa;	/* R14 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
  	pxTopOfStack--;
  	*pxTopOfStack = ( StackType_t ) 0x12121212;	/* R12 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x11111111;	/* R11 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x10101010;	/* R10 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x09090909;	/* R9 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x08080808;	/* R8 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x07070707;	/* R7 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x06060606;	/* R6 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x05050505;	/* R5 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x04040404;	/* R4 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x03030303;	/* R3 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x02020202;	/* R2 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x01010101;	/* R1 */
  	pxTopOfStack--;	
  
  	/* When the task starts is will expect to find the function parameter in
  	R0. */
  	*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
  	pxTopOfStack--;
  
  	/* The status register is set for system mode, with interrupts enabled. */
  	*pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
  
  	#ifdef THUMB_INTERWORK
  	{
  		/* We want the task to start in thumb mode. */
  		*pxTopOfStack |= portTHUMB_MODE_BIT;
  	}
  	#endif
  
  	pxTopOfStack--;
  
  	/* Interrupt flags cannot always be stored on the stack and will
  	instead be stored in a variable, which is then saved as part of the
  	tasks context. */
  	*pxTopOfStack = portNO_CRITICAL_NESTING;
  
  	return pxTopOfStack;	
  }
  /*-----------------------------------------------------------*/
  
  BaseType_t xPortStartScheduler( void )
  {
  extern void vPortISRStartFirstTask( void );
  
  	/* Start the timer that generates the tick ISR.  Interrupts are disabled
  	here already. */
  	prvSetupTimerInterrupt();
  
  	/* Start the first task. */
  	vPortISRStartFirstTask();	
  
  	/* Should not get here! */
  	return 0;
  }
  /*-----------------------------------------------------------*/
  
  void vPortEndScheduler( void )
  {
  	/* It is unlikely that the ARM port will require this function as there
  	is nothing to return to.  */
  }
  /*-----------------------------------------------------------*/
  
  static void prvSetupTimerInterrupt( void )
  {
  EIC_IRQInitTypeDef  EIC_IRQInitStructure;	
  TB_InitTypeDef      TB_InitStructure;
  
  	/* Setup the EIC for the TB. */
  	EIC_IRQInitStructure.EIC_IRQChannelCmd = ENABLE;
  	EIC_IRQInitStructure.EIC_IRQChannel = TB_IRQChannel;
  	EIC_IRQInitStructure.EIC_IRQChannelPriority = 1;
  	EIC_IRQInit(&EIC_IRQInitStructure);
  	
  	/* Setup the TB for the generation of the tick interrupt. */
  	TB_InitStructure.TB_Mode = TB_Mode_Timing;
  	TB_InitStructure.TB_CounterMode = TB_CounterMode_Down;
  	TB_InitStructure.TB_Prescaler = portPRESCALE - 1;
  	TB_InitStructure.TB_AutoReload = ( ( configCPU_CLOCK_HZ / portPRESCALE ) / configTICK_RATE_HZ );
  	TB_Init(&TB_InitStructure);
  	
  	/* Enable TB Update interrupt */
  	TB_ITConfig(TB_IT_Update, ENABLE);
  
  	/* Clear TB Update interrupt pending bit */
  	TB_ClearITPendingBit(TB_IT_Update);
  
  	/* Enable TB */
  	TB_Cmd(ENABLE);
  }
  /*-----------------------------------------------------------*/
  
  
  
  
  
  
  
  