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torturecell
torturecell
Associate II
August 22, 2013
Question

gdb and external memory

  • August 22, 2013
  • 4 replies
  • 1335 views
Posted on August 22, 2013 at 16:35

Hello Everyone,

I am using stm32f407 which is interfaced with 1MB of external RAM. Linker script is a simple one where it puts the data and bss section in external RAM.

Regarding code execution I don;t have an issue. When i try to read any variable which is allocated in external RAM via GDB, i get an error ''Cannot access memory at address 0x60000xxx''

So my question is, is it possible to directly access variables allocated in external memory with normal gdb commands like ''p variable_name''. I can of-course write a function which can copy data from external RAM to internal ram and then i  manually typecast it to get the desired result.
    This topic has been closed for replies.

    4 replies

    frankmeyer9
    frankmeyer9
    Associate III
    August 23, 2013
    Posted on August 23, 2013 at 09:39

    I never got too deep into details about GDB, but your main problem is, the external RAM actually does not exist until you enabled and configured the FSMC (ext. memory interface).

    You will need to hack the startup code to add your FSMC config code before accessing it via gdb, but probably after setting the system clock.

    torturecell
    torturecellAuthor
    Associate II
    August 23, 2013
    Posted on August 23, 2013 at 15:55

    Hi,

    external memory is configured first thing after startup and it is accessible from the code.  Also, I am  trying to access external memory via gdb once the code is up and running. The problem is gdb doesn't know how to access external memory, cause external memory cannot be read directly. GDB has to somehow send command to FSMC via jtag and read external memory

    mailmail9116
    mailmail9116
    Associate III
    August 25, 2013
    Posted on August 25, 2013 at 19:05 Hi , From my experience there is no problem what so ever if the FSMC is configured correctly , i am doing so every day , what evaluation board are you using ? is the memory bank address is correct ? ( i.e on my stm3240g-eval the address starts from 0x64000xxx , the second issue as i mentioned before is maybe the FSMC is not configured correctly , try the following code and see if it works for you : 

    void SystemInit_ExtMemCtl(void)
{
FSMC_NORSRAMInitTypeDef FSMC_NORSRAMInitStructure;
FSMC_NORSRAMTimingInitTypeDef p;
GPIO_InitTypeDef GPIO_InitStructure;
/* Enable GPIOs clock */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD | RCC_AHB1Periph_GPIOE | RCC_AHB1Periph_GPIOF |
RCC_AHB1Periph_GPIOG, ENABLE);
/* Enable FSMC clock */
RCC_AHB3PeriphClockCmd(RCC_AHB3Periph_FSMC, ENABLE);
/*-- GPIOs Configuration -----------------------------------------------------*/
/*
+-------------------+--------------------+------------------+------------------+
| PD0 <-> FSMC_D2 | PE0 <-> FSMC_NBL0 | PF0 <-> FSMC_A0 | PG0 <-> FSMC_A10 |
| PD1 <-> FSMC_D3 | PE1 <-> FSMC_NBL1 | PF1 <-> FSMC_A1 | PG1 <-> FSMC_A11 |
| PD4 <-> FSMC_NOE | PE2 <-> FSMC_A23 | PF2 <-> FSMC_A2 | PG2 <-> FSMC_A12 |
| PD5 <-> FSMC_NWE | PE3 <-> FSMC_A19 | PF3 <-> FSMC_A3 | PG3 <-> FSMC_A13 |
| PD8 <-> FSMC_D13 | PE4 <-> FSMC_A20 | PF4 <-> FSMC_A4 | PG4 <-> FSMC_A14 |
| PD9 <-> FSMC_D14 | PE5 <-> FSMC_A21 | PF5 <-> FSMC_A5 | PG5 <-> FSMC_A15 |
| PD10 <-> FSMC_D15 | PE6 <-> FSMC_A22 | PF12 <-> FSMC_A6 | PG9 <-> FSMC_NE2 |
| PD11 <-> FSMC_A16 | PE7 <-> FSMC_D4 | PF13 <-> FSMC_A7 |------------------+
| PD12 <-> FSMC_A17 | PE8 <-> FSMC_D5 | PF14 <-> FSMC_A8 |
| PD13 <-> FSMC_A18 | PE9 <-> FSMC_D6 | PF15 <-> FSMC_A9 |
| PD14 <-> FSMC_D0 | PE10 <-> FSMC_D7 |------------------+
| PD15 <-> FSMC_D1 | PE11 <-> FSMC_D8 |
+-------------------| PE12 <-> FSMC_D9 |
| PE13 <-> FSMC_D10 |
| PE14 <-> FSMC_D11 |
| PE15 <-> FSMC_D12 |
+--------------------+
*/
/* GPIOD configuration */
GPIO_PinAFConfig(GPIOD, GPIO_PinSource0, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource1, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource4, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource5, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource8, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource9, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource10, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource11, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource12, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource13, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource14, GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOD, GPIO_PinSource15, GPIO_AF_FSMC);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_4 | GPIO_Pin_5 |
GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11 |
GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOD, &GPIO_InitStructure);
/* GPIOE configuration */
GPIO_PinAFConfig(GPIOE, GPIO_PinSource0 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource1 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource2 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource3 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource4 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource5 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource6 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource7 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource8 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource9 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource10 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource11 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource12 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource13 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource14 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOE, GPIO_PinSource15 , GPIO_AF_FSMC);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3 |
GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7 |
GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11|
GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_Init(GPIOE, &GPIO_InitStructure);
/* GPIOF configuration */
GPIO_PinAFConfig(GPIOF, GPIO_PinSource0 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource1 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource2 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource3 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource4 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource5 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource12 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource13 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource14 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOF, GPIO_PinSource15 , GPIO_AF_FSMC);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3 |
GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_12 | GPIO_Pin_13 |
GPIO_Pin_14 | GPIO_Pin_15;
GPIO_Init(GPIOF, &GPIO_InitStructure);
/* GPIOG configuration */
GPIO_PinAFConfig(GPIOG, GPIO_PinSource0 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource1 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource2 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource3 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource4 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource5 , GPIO_AF_FSMC);
GPIO_PinAFConfig(GPIOG, GPIO_PinSource9 , GPIO_AF_FSMC);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3 |
GPIO_Pin_4 | GPIO_Pin_5 |GPIO_Pin_9;
GPIO_Init(GPIOG, &GPIO_InitStructure);
/*-- FSMC Configuration ------------------------------------------------------*/
p.FSMC_AddressSetupTime = 3;
p.FSMC_AddressHoldTime = 0;
p.FSMC_DataSetupTime = 6;
p.FSMC_BusTurnAroundDuration = 1;
p.FSMC_CLKDivision = 0;
p.FSMC_DataLatency = 0;
p.FSMC_AccessMode = FSMC_AccessMode_A;
FSMC_NORSRAMInitStructure.FSMC_Bank = FSMC_Bank1_NORSRAM2;
FSMC_NORSRAMInitStructure.FSMC_DataAddressMux = FSMC_DataAddressMux_Disable;
FSMC_NORSRAMInitStructure.FSMC_MemoryType = FSMC_MemoryType_PSRAM;
FSMC_NORSRAMInitStructure.FSMC_MemoryDataWidth = FSMC_MemoryDataWidth_16b;
FSMC_NORSRAMInitStructure.FSMC_BurstAccessMode = FSMC_BurstAccessMode_Disable;
FSMC_NORSRAMInitStructure.FSMC_AsynchronousWait = FSMC_AsynchronousWait_Disable;
FSMC_NORSRAMInitStructure.FSMC_WaitSignalPolarity = FSMC_WaitSignalPolarity_Low;
FSMC_NORSRAMInitStructure.FSMC_WrapMode = FSMC_WrapMode_Disable;
FSMC_NORSRAMInitStructure.FSMC_WaitSignalActive = FSMC_WaitSignalActive_BeforeWaitState;
FSMC_NORSRAMInitStructure.FSMC_WriteOperation = FSMC_WriteOperation_Enable;
FSMC_NORSRAMInitStructure.FSMC_WaitSignal = FSMC_WaitSignal_Disable;
FSMC_NORSRAMInitStructure.FSMC_ExtendedMode = FSMC_ExtendedMode_Disable;
FSMC_NORSRAMInitStructure.FSMC_WriteBurst = FSMC_WriteBurst_Disable;
FSMC_NORSRAMInitStructure.FSMC_ReadWriteTimingStruct = &p;
FSMC_NORSRAMInitStructure.FSMC_WriteTimingStruct = &p;
FSMC_NORSRAMInit(&FSMC_NORSRAMInitStructure);
/*!< Enable FSMC Bank1_SRAM2 Bank */
FSMC_NORSRAMCmd(FSMC_Bank1_NORSRAM2, ENABLE);
}

    Best regards, Michael
    Tesla DeLorean
    Tesla DeLorean
    Guru
    August 25, 2013
    Posted on August 25, 2013 at 20:12

    GDB has to somehow send command to FSMC via jtag and read external memory

    Well at the processor level the memory accesses in the same ways as any other, the earlier points were about initializing the interface, or associated buses. I'm not using GDB, but other debug environments often have initialization files that poke system registers to bring up external memory interfaces, SDRAM, and the like. Check if GDB needs some .INI file. Further check if it needs a linker script, or equivalent file, that describes the memory map it's supposed to be using.
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