Does anyone have any MPU code that just works? STM32F103VG

Posted on May 17, 2011 at 14:26

Required MPU basic operation:

1)

     

Protect a section of RAM.

2)

     

Access the RAM.

3)

     

Run the exception routine

My setup is a motor-control application presently utilising timer interrupts, A2D interrupts, and DMA transfers - STM32F103VG, has MPU/has 96kB RAM, all working nicely, except a demo MPU feature:

#define SIZEOF_PROTMEM            0x4000        //16kB;

#define ADDRESS_OF_PROTECTED_SRAM (SRAM_BASE + 0x14000)

volatile __root __no_init u32 au32MyProtectedBuffer[SIZEOF_PROTMEM/sizeof(u32)] @ ADDRESS_OF_PROTECTED_SRAM;

       //Disable MPU

       MPU_Disable();

       //Turn off all regions - the reset states for the ENA bits are undefined.

       //No-one else seems to do this – but just for fun OK?

       for(u32 u32Rgn=0 ; u32Rgn < ((MPU->TYPE&MPU_TYPE_DREGION_Msk) >> MPU_TYPE_DREGION_Pos) ; u32Rgn++)

       {

              MPU->RNR  = MPU_RNR_REGION_Msk & (u32Rgn << MPU_RNR_REGION_Pos);

              MPU->RASR = 0;

       };

       //

       //Configure a no access MPU region for the 16 KB of RAM.

       //This region is used for demonstrating an MPU exception.

       //

       sMPUInit.regionEnable = TRUE;

       sMPUInit.regionNo = 0;

       sMPUInit.baseAddress = ADDRESS_OF_PROTECTED_SRAM;

       sMPUInit.size = mpuRegionSize16Kb;

       sMPUInit.accessPermission = mpuRegionNoAccess;

       sMPUInit.disableExec = TRUE;

       sMPUInit.shareable = FALSE;

       sMPUInit.cacheable = TRUE;

       sMPUInit.bufferable = TRUE;

       sMPUInit.srd = 0xFF;

       sMPUInit.tex = 0;

       MPU_ConfigureRegion(&sMPUInit);

       //Enable the Memory Manage Handler

       NVIC_SystemHandlerPriorityConfig(SystemHandler_MemoryManage, 2, 8);

      

       //Enable memory protection and mem fault exceptions – background is Priv-mode open access – courtesy MPU_CTRL_PRIVDEFENA bit.

       MPU_Enable(MPU_CTRL_ENABLE_Msk | MPU_CTRL_PRIVDEFENA_Msk);

My trip code:

void SimulateMemoryViolation(void)

{

       //Access the forbidden memory!

       au32MyProtectedBuffer[0]++;

}

My exception handler which is not being called when I call

SimulateMemoryViolation(),

called from stub in

MemManage_Handler():

void EH_MemoryViolation(void)

{

       SCB->SHCSR &= ~SCB_SHCSR_MEMFAULTACT;           //clear the fault flag

       //Go to infinite loop when Memory Manage exception occurs

       SetScreen_MPU_Error();

}

Other symptoms: In other variations of this setup (ie. specify code blocks, peripheral blocks, User/Priv permissions etc) I can generate MPU exceptions, or hard faults , but not from accessing my “protected ram.�?

Posted on May 17, 2011 at 14:26

No - because ''just works'' is meaningless!

You need to specify exactly what ''work'' you want it to do - and in what environment.

Posted on May 17, 2011 at 14:26

Oh, great.

Now I see it.

The SRD disables the regions if set to 1.

Profoundly embarrassed.

Anyhow, now it's throwing hardware faults when 

SimulateMemoryViolation()

called, not mem-handler exceptions - any observations?

Does anyone just have code that ''just works?''

Ta

Posted on May 17, 2011 at 14:26

As I recall the STM32F103 series doesn't have the MPU included in the M3 core.  I believe you have to move the the STM32F200 series for that.

 

I think you'll find the STM32F103xF/103xG (ie XL devices) are claiming to have one

http://www.datasheetarchive.com/Indexer/Datasheet-099/DSA00188765.html

I'd guess I'd start by looking at the code generated for

void SimulateMemoryViolation(void);

Posted on May 17, 2011 at 14:26

As I recall the STM32F103 series doesn't have the MPU included in the M3 core.  I believe you have to move the the STM32F200 series for that.

  Jack Peacock

Posted on May 17, 2011 at 14:26

The original post was too long to process during our migration. Please click on the provided URL to read the original post. https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I6a0&d=%2Fa%2F0X0000000br8%2Fxnny1Gkfby5b1IH5cYt7qxfEqnBho68CRUBhcosoX4Y&asPdf=false

Posted on May 17, 2011 at 14:26

OK, so bottom line is, if you invoke an MPU fault from within an exception or interrupt handler, then a hard fault is called.  So you must call SimulateMemoryViolation() from the main line.

MPU code that ''just works'' attempt to attach #5.

To use the code.

1)

     

Copy stm32f10x_mpu.c/.h into your StdPeriphLibrary folder.

2)

     

Copy memprot.c/.h into your project files folder.

3)

     

Customise memprot.c as required for your ap.

4)

     

Call

InitMemProt()

from

main()

.

5)

     

Somewhere in your mainline, call

SimulateMemoryViolation()

.

6)

 

In the mem_fault exception handler (in stm32f10x_it.c), place a stub to call

EH_MemoryViolation(),

like this:

void MemManage_Handler(void)

{

     EH_MemoryViolation();

}

7)

     

Enjoy.

Luke

(may the source be with you)