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openblt/Target/Demo/ARMCM3_LM3S_EK_LM3S6965_IAR/Boot/shared_params.c

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/************************************************************************************//**
* \file Demo/ARMCM3_LM3S_EK_LM3S6965_IAR/Boot/shared_params.c
* \brief Shared RAM parameters source file.
* \ingroup Boot_ARMCM3_LM3S_EK_LM3S6965_IAR
* \internal
*----------------------------------------------------------------------------------------
* C O P Y R I G H T
*----------------------------------------------------------------------------------------
* Copyright (c) 2018 by Feaser http://www.feaser.com All rights reserved
*
*----------------------------------------------------------------------------------------
* L I C E N S E
*----------------------------------------------------------------------------------------
* This file is part of OpenBLT. OpenBLT is free software: you can redistribute it and/or
* modify it under the terms of the GNU General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option) any later
* version.
*
* OpenBLT 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 have received a copy of the GNU General Public License along with OpenBLT. It
* should be located in ".\Doc\license.html". If not, contact Feaser to obtain a copy.
*
* \endinternal
****************************************************************************************/
/****************************************************************************************
* Include files
****************************************************************************************/
#include <stddef.h> /* Standard definitions (NULL). */
#include "shared_params.h" /* Shared parameters header. */
/****************************************************************************************
* Macro definitions
****************************************************************************************/
/** \brief Constant parameter buffer identifier. This value is always located as the
* start of the buffer to validate the the RAM contains valid shared parameters.
*/
#define SHARED_PARAMS_BUFFER_ID (0xCE42E7A2u)
/****************************************************************************************
* Type definitions
****************************************************************************************/
/** \brief Layout of the shared parameters RAM buffer. */
typedef struct t_shared_params_buffer
{
/** \brief Fixed buffer identifier to validate that the RAM contains valid shared
* parameters.
*/
uint32_t identifier;
/** \brief Array for the actual parameter data. */
uint8_t data[SHARED_PARAMS_CFG_BUFFER_DATA_LEN];
/** \brief Checksum value of all the bytes in the buffer, excluding this checksum
* value of obvious reasons. The checksum is calculated as the Two's
* complement of the sum of the bytes.
*/
uint16_t checksum;
} tSharedParamsBuffer;
/****************************************************************************************
* Global data declarations
****************************************************************************************/
/** \brief Declaration of the actual parameter buffer that this module manages.
* \warning For the shared RAM parameters to work properly for sharing information
* between the bootloader and user program, it is important that this
* variable is linked to the exact same RAM address in both the bootloader
* and the user program. Additionally, it should be configured such that the
* C-startup code does NOT zero its contents during system initialization. This
* is the code that runs in the reset event handler, before function main() is
* called.
* For GCC based embedded toolchains, the solution is to assign this variable
* to a custom section, in this case called ".shared". Then in the linker
* script, add the following to the SECTIONS:
*
* .shared (NOLOAD) :
* {
* . = ALIGN(4);
* _sshared = .;
* __shared_start__ = _sshared;
* *(.shared)
* *(.shared.*)
* KEEP(*(.shared))
* . = ALIGN(4);
* _eshared = .;
* __shared_end__ = _eshared;
* } >SHARED
*
* Next, add a new MEMORY entry for SHARED at the start of RAM and reduce
* the length of the remaining RAM:
*
* SHARED (xrw) : ORIGIN = 0x200000C0, LENGTH = 64
* RAM (xrw) : ORIGIN = 0x20000100, LENGTH = 32K - 192 - 64
*
* Note that the previous example is for an STM32F0 microcontroller where
* the first 192 (0xC0) bytes in RAM are reserved for the user program
* vector table.
*
* \remark This same approach can be applied with other toolchains such as Keil MDK
* and IAR EWARM. Consult the compiler and linker user manuals of your
* toolchain to find out how to place a RAM variable at a fixed memory address
* and to prevent the C-startup code from zeroing its contents.
* Here are a few links to get you started:
* * IAR EWARM:
* https://www.iar.com/support/tech-notes/compiler/
* linker-error-for-absolute-located-variable/
* * Keil MDK:
* http://www.keil.com/support/docs/3480.htm
*/
__no_init static tSharedParamsBuffer sharedParamsBuffer @ ".shared";
/****************************************************************************************
* Function prototypes
****************************************************************************************/
static bool SharedParamsValidateBuffer(void);
static void SharedParamsWriteChecksum(void);
static bool SharedParamsVerifyChecksum(void);
static uint16_t SharedParamsCalculateChecksum(void);
/************************************************************************************//**
** \brief Initializes the shared RAM parameters module.
** \return none.
**
****************************************************************************************/
void SharedParamsInit(void)
{
uint32_t byteIdx;
/* The shared parameter buffer does not get initialized by the C-startup code. Another
* previously running program could have initialized it, in which case it is ready
* for use and nothing more needs to be done.
*/
if (!SharedParamsValidateBuffer())
{
/* The shared parameter buffer was not yet initialized by a running program. This
* typically happens after a cold reset where the RAM contents were lost. In this
* case we need to explicitly configure and initialize it, since the C-startup code
* was configured to not do this.
*
* The initialization consists of setting the buffer identifier, zeroing the
* actual parameter data and updating the checksum at the end.
*/
sharedParamsBuffer.identifier = SHARED_PARAMS_BUFFER_ID;
for (byteIdx=0; byteIdx < SHARED_PARAMS_CFG_BUFFER_DATA_LEN; byteIdx++)
{
sharedParamsBuffer.data[byteIdx] = 0;
}
SharedParamsWriteChecksum();
}
} /*** end of SharedParamsInit ***/
/************************************************************************************//**
** \brief Reads a data byte from the shared parameter buffer at the specified index.
** \param idx Index into the parameter data array. A valid value is between 0 and
** (SHARED_PARAMS_CFG_BUFFER_DATA_LEN - 1).
** \param value Pointer to where the read data value is stored.
** \return True if successful, false otherwise.
**
****************************************************************************************/
bool SharedParamsReadByIndex(uint32_t idx, uint8_t * value)
{
bool result = false;
/* Only continue if the buffer and the specified parameters are valid. */
if ( (SharedParamsValidateBuffer()) &&
(idx < SHARED_PARAMS_CFG_BUFFER_DATA_LEN) &&
(value != NULL) )
{
/* Read the value and update the result. */
*value = sharedParamsBuffer.data[idx];
result = true;
}
/* Give the result back to the caller. */
return result;
} /*** end of SharedParamsReadByIndex ***/
/************************************************************************************//**
** \brief Writes a data byte to the shared parameter buffer at the specified index.
** \param idx Index into the parameter data array. A valid value is between 0 and
** (SHARED_PARAMS_CFG_BUFFER_DATA_LEN - 1).
** \param value Value to write.
** \return True if successful, false otherwise.
**
****************************************************************************************/
bool SharedParamsWriteByIndex(uint32_t idx, uint8_t value)
{
bool result = false;
/* Only continue if the buffer and the specified parameters are valid. */
if ( (SharedParamsValidateBuffer()) &&
(idx < SHARED_PARAMS_CFG_BUFFER_DATA_LEN) )
{
/* Write the value. */
sharedParamsBuffer.data[idx] = value;
/* Update the checksum since the contents were just changed. */
SharedParamsWriteChecksum();
/* Update the result. */
result = true;
}
/* Give the result back to the caller. */
return result;
} /*** end of SharedParamsWriteByIndex ***/
/************************************************************************************//**
** \brief Validates the shared parameter buffer contents by looking at the table
** identifier and verifying its checksum.
** \return True if successful, false otherwise.
**
****************************************************************************************/
static bool SharedParamsValidateBuffer(void)
{
bool result = false;
/* Perform validation. */
if ( (sharedParamsBuffer.identifier == SHARED_PARAMS_BUFFER_ID) &&
(SharedParamsVerifyChecksum()) )
{
/* The shared parameter buffer is valid, so update the result value. */
result = true;
}
/* Give the result back to the caller. */
return result;
} /*** end of SharedParamsValitabeTable ***/
/************************************************************************************//**
** \brief Calculates and writes the checksum into the buffer.
** \return none.
**
****************************************************************************************/
static void SharedParamsWriteChecksum(void)
{
/* Calculate and write the checksum. */
sharedParamsBuffer.checksum = SharedParamsCalculateChecksum();
} /*** end of SharedParamsWriteChecksum ***/
/************************************************************************************//**
** \brief Calculates and verifies the checksum that is currently present in the
** buffer.
** \return True is the checksum is correct, false otherwise.
**
****************************************************************************************/
static bool SharedParamsVerifyChecksum(void)
{
bool result = false;
/* Calculate and verify the checksum. */
if (SharedParamsCalculateChecksum() == sharedParamsBuffer.checksum)
{
/* Checksum is correct, so update the result value. */
result = true;
}
/* Give the result back to the caller. */
return result;
} /*** end of SharedParamsVerifyChecksum ***/
/************************************************************************************//**
** \brief Calculates and returns the checksum value for the current contents in the
** buffer. The checksum is calculated by taking the sum of all bytes in the
** parameter buffer (excluding the checksum at the end) and them taking the
** two's complement value of it.
** \return The calculated checksum value.
**
****************************************************************************************/
static uint16_t SharedParamsCalculateChecksum(void)
{
uint16_t result = 0;
uint32_t byteIdx;
/* Add the identifier bytes to the checksum. */
result += (uint8_t)sharedParamsBuffer.identifier;
result += (uint8_t)(sharedParamsBuffer.identifier >> 8u);
result += (uint8_t)(sharedParamsBuffer.identifier >> 16u);
result += (uint8_t)(sharedParamsBuffer.identifier >> 24u);
/* Loop through the parameter data array. */
for (byteIdx=0; byteIdx<SHARED_PARAMS_CFG_BUFFER_DATA_LEN; byteIdx++)
{
/* Add parameter data byte to the checksum. */
result += (uint8_t)sharedParamsBuffer.data[byteIdx];
}
/* Determine one's complement. */
result = ~result;
/* Determine two's complement. */
result += 1;
/* Give the result back to the caller. */
return result;
} /*** end of SharedParamsCalculateChecksum ***/
/*********************************** end of shared_params.c ****************************/
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