global array is altered when CAN API initialization occurs

[lpcware]

Content originally posted in LPCWare by christianhdz on Tue Aug 11 14:50:17 MST 2015
I have an array of 256 bytes that is being modified when LPC_CCAN_API->init_can(&CanApiClkInitTable[0], TRUE) is executed. I don't want this array to be modified, I already initialized it after  the  Private types/enumerations/variables

#define TICKRATE_HZ1 (100) /* 1/TickRate_HZ = PERIOD MS, 20 ms */

#define TEST_CCAN_BAUD_RATE 500000

CCAN_MSG_OBJ_T msg_obj;

[color=#66f]uint8_t crc8table[256] = {
    0x00, 0x1D, 0x3A, 0x27, 0x74, 0x69, 0x4E, 0x53,
    0xE8, 0xF5, 0xD2, 0xCF, 0x9C, 0x81, 0xA6, 0xBB,
    0xCD, 0xD0, 0xF7, 0xEA, 0xB9, 0xA4, 0x83, 0x9E,
    0x25, 0x38, 0x1F, 0x02, 0x51, 0x4C, 0x6B, 0x76,
...}; 
[/color]

When I debug the program I observe that some of the values of my array are modified i.e. crc8table[0x6A], it is changed to ZERO. Other array elements are also changed to zero.

I observe that it happens when line LPC_CCAN_API->init_can(&CanApiClkInitTable[0], TRUE); is executed

int main(void)
{

uint32_t CanApiClkInitTable[2];
/* Publish CAN Callback Functions */
CCAN_CALLBACKS_T callbacks = {
CAN_rx,
CAN_tx,
CAN_error,
NULL,
NULL,
NULL,
NULL,
NULL,
};
SystemCoreClockUpdate();
Board_Init();

/* Enable and setup SysTick Timer at a periodic rate */
SysTick_Config(SystemCoreClock/ TICKRATE_HZ1);


baudrateCalculate(TEST_CCAN_BAUD_RATE, CanApiClkInitTable);

[color=#f00]LPC_CCAN_API->init_can(&CanApiClkInitTable[0], TRUE);[/color]
/* Configure the CAN callback functions */
LPC_CCAN_API->config_calb(&callbacks);

If I try restoring the values of the array to the original value, then I get a HARD_FAULT_HANDLER call.

Any idea why this is happening and how to avoid it?

I am using an LPC11C24 board, using lpcxpresso 7.9 and I based my program in the CCAN_ROM example from LPC_OPEN example.

[lpcware]

Content originally posted in LPCWare by christianhdz on Mon Aug 17 13:44:04 MST 2015
Indeed! Thanks! This solved the issue.

#include "board.h"
#include "cr_section_macros.h"

/*****************************************************************************
* Private types/enumerations/variables
****************************************************************************/

#define TEST_CCAN_BAUD_RATE 500000

//reserve CAN ROM-RAM 0x1000 0050 - 0x1000 00B9
__BSS(RESERVED) char CAN_driver_memory[0xC0];

CCAN_MSG_OBJ_T msg_obj;
...

[lpcware]

Content originally posted in LPCWare by R2D2 on Mon Aug 17 11:27:08 MST 2015

---

Quote: christianhdz
Is there something I am missing?

---

Yes, section macros 

#include "board.h"
[color=#f00]#include "cr_section_macros.h"[/color]

/*****************************************************************************
 * Private types/enumerations/variables
 ****************************************************************************/

#define TEST_CCAN_BAUD_RATE 500000
[color=#f00]
//reserve CAN ROM-RAM 0x1000 0050 - 0x1000 00B9
__BSS(RESERVED) char CAN_driver_memory[0xC0];
[/color]
CCAN_MSG_OBJ_T msg_obj;
...

[lpcware]

Content originally posted in LPCWare by christianhdz on Mon Aug 17 10:52:26 MST 2015
I am using the CCAN_ROM example included in lpcopen_v2_00a_lpcxpresso_nxp_lpcxpresso_11c24.zip

I tried to use the suggested macro call as follows:

int main(void)
{

uint32_t CanApiClkInitTable[2];
/* Publish CAN Callback Functions */
CCAN_CALLBACKS_T callbacks = {
CAN_rx,
CAN_tx,
CAN_error,
NULL,
NULL,
NULL,
NULL,
NULL,
};

//reserve CAN ROM-RAM 0x1000 0050 - 0x1000 00B9
[color=#66f]__BSS(RESERVED) char CAN_driver_memory[0xC0];[/color]

       SystemCoreClockUpdate();
Board_Init();

/* Enable and setup SysTick Timer at a periodic rate */
SysTick_Config(SystemCoreClock/ TICKRATE_HZ1);

baudrateCalculate(TEST_CCAN_BAUD_RATE, CanApiClkInitTable);

LPC_CCAN_API->init_can(&CanApiClkInitTable[0], TRUE);
/* Configure the CAN callback functions */
LPC_CCAN_API->config_calb(&callbacks);
/* Enable the CAN Interrupt */
NVIC_EnableIRQ(CAN_IRQn);

But I get a bunch of errors with the addition of that line:
[list]
  [*]'RESERVED' undeclared (first use in this function)
  [*]expected ';' before 'char'
  [*]make: *** [example/src/ccan_romIGNSWITCH.o] Error 1
[*]
[/list]

Is there something I am missing?

Thanks for your support

[lpcware]

Content originally posted in LPCWare by R2D2 on Thu Aug 13 14:54:41 MST 2015

---

Quote: christianhdz
I used the "static" modification but the ARRAY is still modified.

---

I'm not sure which sample you are using in detail, so it could be useful to post it 

Either you didn't reserve CAN RAM as described in:

https://www.lpcware.com/content/forum/how-to-reserve-lpc11cxx-ram

or your linker is removing your unused array as explained in:

https://embeddedfreak.wordpress.com/2009/02/10/removing-unused-functionsdead-codes-with-gccgnu-ld/

Since your array is stored in 0x1000 006B that's the RAM area which should be reserved for CAN API 

So adding a simple:

//reserve CAN ROM-RAM 0x1000 0050 - 0x1000 00B9
__BSS(RESERVED) char CAN_driver_memory[0xC0];

should solve your problem 

[lpcware]

Content originally posted in LPCWare by christianhdz on Thu Aug 13 14:38:42 MST 2015
I used the "static" modification but the ARRAY is still modified.
See the attached pictures before and after the execution of line where CAN is initialized.

[color=#f0f]LPC_CCAN_API->init_can(&CanApiClkInitTable[0], TRUE);[/color]

the attached show the example where crc8table[0x6B]=0x5B, and then it is modified (unintentedly) to  crc8table[0x6B]=0x00 (highlighted in yellow in the expressions window).

[lpcware]

Content originally posted in LPCWare by DF9DQ on Wed Aug 12 01:19:45 MST 2015
Could it be that the array occupies the RAM region that should have been reserved for use by the CAN ROM drivers?
Quoting the user manual:

---

Quote:
On-chip RAM from address 0x1000 0050 to 0x1000 00B8 is used by the CAN API. This address range should not be used by the application. For applications using the on-chip CAN API, the linker control file should be modified appropriately to prevent usage of this area for application’s variable storage.

---

[lpcware]

Content originally posted in LPCWare by R2D2 on Tue Aug 11 16:27:14 MST 2015

---

Quote: christianhdz
Any idea why this is happening and how to avoid it?

---

Use:

static uint8_t crc8table[256] = ...