How to write custom (.ld) file?(External Flash Loader)

[erkanc]

Hi everyone. I hope you are well.

I am researching how to write LD file. I listened external flash pins. I used an "External Flash Loader file" to program the external Flash IC and MCU. I used STLDR file that work. 

I will write stages step by step;

0x06 : Write Enable
0x05 : Read status, -> Response: 0x02
0xD8 : Block Erase
0x05 : Read status, -> Response: 0x03
...//Repeat 0x05 command
0x05 : Read status, -> Response: 0x00 // Block erased.
...
0x06 : Write Enable
0x05 : Read status, -> Response: 0x02
0x02 : Page Program
0x05 : Read status, -> Response: 0x03
...//Repeat 0x05 command
0x05 : Read status, -> Response: 0x00 // Page programmed.
...

I created a my custom STLDR file. Programmer(Stm32Cube) is "known" my STLDR file. But My MCU and Flash IC can not be programmed. I take error. And I listened again. My STLDR file use different procedure to program. Is not like above.

0x66 : Reset 0 
0x99 : Reset 1
0x06 : Write Enable
0x20 : Sector Erase
0x05 : Read status bla...bla...
...
//Finally Error

I researched my LD file. I understood "Init" function that is first line. But I can not find how to put other functions. I thought that I can correct the functions according to working STLDR file. 

My LD File:

/*
*****************************************************************************
**  File        : linker.ld
**
**                Set heap size, stack size and stack location according
**                to application requirements.
**
**                Set memory bank area and size if external memory is used.
**
**  Target      : STMicroelectronics STM32
**
*****************************************************************************
*/

/* Entry Point */
ENTRY(Init)

/* Generate 2 segment for Loader code and device info */
PHDRS {Loader PT_LOAD ; SgInfo PT_LOAD ; }

/* Highest address of the user mode stack */
_estack = ORIGIN(RAM_D1) + LENGTH(RAM_D1);    /* end of RAM */
/* Generate a link error if heap and stack don't fit into RAM */
_Min_Heap_Size = 0x200;      /* required amount of heap  */
_Min_Stack_Size = 0x400; /* required amount of stack */

/* Specify the memory areas */
MEMORY
{
RAM_D1 (xrw)      : ORIGIN = 0x20000004, LENGTH = 144K-4
}

/* Define output sections */
SECTIONS
{
  /* The startup code goes first into FLASH */
  
  .isr_vector :
  {
  	. = . + 0x1FC;
    . = ALIGN(4);
    KEEP(*(.isr_vector)) /* Startup code */
    . = ALIGN(4);
  } >RAM_D1 :Loader
  
  

  .ARM.extab   : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >RAM_D1
  .ARM : {
    __exidx_start = .;
    *(.ARM.exidx*)
    __exidx_end = .;
  } >RAM_D1 :Loader

  .preinit_array     :
  {
    PROVIDE_HIDDEN (__preinit_array_start = .);
    KEEP (*(.preinit_array*))
    PROVIDE_HIDDEN (__preinit_array_end = .);
  } >RAM_D1 :Loader
  
  .init_array :
  {
    PROVIDE_HIDDEN (__init_array_start = .);
    KEEP (*(SORT(.init_array.*)))
    KEEP (*(.init_array*))
    PROVIDE_HIDDEN (__init_array_end = .);
  } >RAM_D1 :Loader
  
  .fini_array :
  {
    PROVIDE_HIDDEN (__fini_array_start = .);
    KEEP (*(SORT(.fini_array.*)))
    KEEP (*(.fini_array*))
    PROVIDE_HIDDEN (__fini_array_end = .);
  } >RAM_D1 :Loader

  /* used by the startup to initialize data */
  _sidata = LOADADDR(.data);

  /* Initialized data sections goes into RAM, load LMA copy after code */
  .data : 
  {
    . = ALIGN(4);
    _sdata = .;        /* create a global symbol at data start */
    *(.data)           /* .data sections */
    *(.data*)          /* .data* sections */

    . = ALIGN(4);
    _edata = .;        /* define a global symbol at data end */
  } >RAM_D1 :Loader

  
  /* Uninitialized data section */
  . = ALIGN(4);
  .bss :
  {
    /* This is used by the startup in order to initialize the .bss secion */
    _sbss = .;         /* define a global symbol at bss start */
    __bss_start__ = _sbss;
    *(.bss)
    *(.bss*)
    *(COMMON)

    . = ALIGN(4);
    _ebss = .;         /* define a global symbol at bss end */
    __bss_end__ = _ebss;
  } >RAM_D1 :Loader

  /* The program code and other data goes into FLASH */
  .text :
  {
    . = ALIGN(4);
    *(.text)           /* .text sections (code) */
    *(.text*)          /* .text* sections (code) */
    *(.glue_7)         /* glue arm to thumb code */
    *(.glue_7t)        /* glue thumb to arm code */
    *(.eh_frame)

    KEEP (*(.init))
    KEEP (*(.fini))
	KEEP (*Loader_Src.o ( .text* ))
    . = ALIGN(4);
    _etext = .;        /* define a global symbols at end of code */
  } >RAM_D1 :Loader
  
  .Dev_Info :
  {
  	__Dev_info_START = .;
  	*(.Dev_info*)
  	KEEP(*(.Dev_info))
  	__Dev_info_END = .;
  } >RAM_D1 :SgInfo
  
  
  /* Constant data goes into FLASH */
  .rodata :
  {
    . = ALIGN(4);
    *(.rodata)         /* .rodata sections (constants, strings, etc.) */
    *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
    . = ALIGN(4);
  } >RAM_D1 :Loader
  
  
  /* User_heap_stack section, used to check that there is enough RAM left */
  ._user_heap_stack :
  {
    . = ALIGN(4);
    PROVIDE ( end = . );
    PROVIDE ( _end = . );
    . = . + _Min_Heap_Size;
    . = . + _Min_Stack_Size;
    . = ALIGN(4);
  } >RAM_D1 :Loader

  .ARM.attributes 0 : { *(.ARM.attributes) }
}

I use MX25L6433F as external flash IC. And I find the driver following link;

https://controllerstech.com/w25q-flash-series-part-9-spi-flash-loader/

I wonder where is name of other functions in LD file. 

For example; the "Init" function is in <Loader_Src.c>.

/* Entry Point */
ENTRY(Init)

Loader_Src.c

#include "W25Qxx.h"
#include "main.h"
#include "gpio.h"
#include "spi.h"

#define LOADER_OK   0x1
#define LOADER_FAIL 0x0
extern void SystemClock_Config(void);

/**
 * @brief  System initialization.
 *   None
 * @retval  LOADER_OK = 1   : Operation succeeded
 * @retval  LOADER_FAIL = 0 : Operation failed
 */
int Init(void) {

    //*(uint32_t*)0xE000EDF0 = 0xA05F0000; //enable interrupts in debug


    SystemInit();

    /* ADAPTATION TO THE DEVICE
     *
     * change VTOR setting for H7 device
     * SCB->VTOR = 0x24000000 | 0x200;
     *
     * change VTOR setting for other devices
     * SCB->VTOR = 0x20000000 | 0x200;
     *
     * */

    SCB->VTOR = 0x20000000 | 0x200;

    __set_PRIMASK(0); //enable interrupts

    HAL_Init();

    SystemClock_Config();

    MX_GPIO_Init();

    __HAL_RCC_SPI2_FORCE_RESET();  //completely reset peripheral
    __HAL_RCC_SPI2_RELEASE_RESET();

    MX_SPI2_Init();

    flash_Reset();

    __set_PRIMASK(1); //disable interrupts
    return LOADER_OK;
}

/**
 * @brief   Program memory.
 *    Address: page address
 *    Size   : size of data
 *    buffer : pointer to data buffer
 * @retval  LOADER_OK = 1       : Operation succeeded
 * @retval  LOADER_FAIL = 0 : Operation failed
 */
int Write(uint32_t Address, uint32_t Size, uint8_t* buffer) {

    __set_PRIMASK(0); //enable interrupts

    flash_WriteMemory(buffer, Address, Size);

    __set_PRIMASK(1); //disable interrupts
    return LOADER_OK;
}

int Read (uint32_t Address, uint32_t Size, uint8_t* buffer){
    __set_PRIMASK(0); //enable interrupts

	flash_ReadMemory(Address, Size, buffer);

    __set_PRIMASK(1); //disable interrupts
	return 1;
}

/**
 * @brief   Sector erase.
 *    EraseStartAddress :  erase start address
 *    EraseEndAddress   :  erase end address
 * @retval  LOADER_OK = 1       : Operation succeeded
 * @retval  LOADER_FAIL = 0 : Operation failed
 */
int SectorErase(uint32_t EraseStartAddress, uint32_t EraseEndAddress) {

    __set_PRIMASK(0); //enable interrupts

    flash_SectorErase(EraseStartAddress, EraseEndAddress);

    __set_PRIMASK(1); //disable interrupts
    return LOADER_OK;
}

/**
 * Description :
 * Mass erase of external flash area
 * Optional command - delete in case usage of mass erase is not planed
 * Inputs    :
 *      none
 * outputs   :
 *     none
 * Note: Optional for all types of device
 */
int MassErase(void) {

    __set_PRIMASK(0); //enable interrupts

    flash_ChipErase();

    __set_PRIMASK(1); //disable interrupts
    return LOADER_OK;
}

/**
 * Description :
 * Calculates checksum value of the memory zone
 * Inputs    :
 *      StartAddress  : Flash start address
 *      Size          : Size (in WORD)
 *      InitVal       : Initial CRC value
 * outputs   :
 *     R0             : Checksum value
 * Note: Optional for all types of device
 */
uint32_t CheckSum(uint32_t StartAddress, uint32_t Size, uint32_t InitVal) {
    uint8_t missalignementAddress = StartAddress % 4;
    uint8_t missalignementSize = Size;
    int cnt;
    uint32_t Val;

    StartAddress -= StartAddress % 4;
    Size += (Size % 4 == 0) ? 0 : 4 - (Size % 4);

    for (cnt = 0; cnt < Size; cnt += 4) {
        Val = *(uint32_t*) StartAddress;
        if (missalignementAddress) {
            switch (missalignementAddress) {
                case 1:
                    InitVal += (uint8_t) (Val >> 8 & 0xff);
                    InitVal += (uint8_t) (Val >> 16 & 0xff);
                    InitVal += (uint8_t) (Val >> 24 & 0xff);
                    missalignementAddress -= 1;
                    break;
                case 2:
                    InitVal += (uint8_t) (Val >> 16 & 0xff);
                    InitVal += (uint8_t) (Val >> 24 & 0xff);
                    missalignementAddress -= 2;
                    break;
                case 3:
                    InitVal += (uint8_t) (Val >> 24 & 0xff);
                    missalignementAddress -= 3;
                    break;
            }
        } else if ((Size - missalignementSize) % 4 && (Size - cnt) <= 4) {
            switch (Size - missalignementSize) {
                case 1:
                    InitVal += (uint8_t) Val;
                    InitVal += (uint8_t) (Val >> 8 & 0xff);
                    InitVal += (uint8_t) (Val >> 16 & 0xff);
                    missalignementSize -= 1;
                    break;
                case 2:
                    InitVal += (uint8_t) Val;
                    InitVal += (uint8_t) (Val >> 8 & 0xff);
                    missalignementSize -= 2;
                    break;
                case 3:
                    InitVal += (uint8_t) Val;
                    missalignementSize -= 3;
                    break;
            }
        } else {
            InitVal += (uint8_t) Val;
            InitVal += (uint8_t) (Val >> 8 & 0xff);
            InitVal += (uint8_t) (Val >> 16 & 0xff);
            InitVal += (uint8_t) (Val >> 24 & 0xff);
        }
        StartAddress += 4;
    }

    return (InitVal);
}

/**
 * Description :
 * Verify flash memory with RAM buffer and calculates checksum value of
 * the programmed memory
 * Inputs    :
 *      FlashAddr     : Flash address
 *      RAMBufferAddr : RAM buffer address
 *      Size          : Size (in WORD)
 *      InitVal       : Initial CRC value
 * outputs   :
 *     R0             : Operation failed (address of failure)
 *     R1             : Checksum value
 * Note: Optional for all types of device
 */
uint64_t Verify (uint32_t MemoryAddr, uint32_t RAMBufferAddr, uint32_t Size, uint32_t missalignement){
	__set_PRIMASK(0); //enable interrupts
	
	uint32_t VerifiedData = 0, InitVal = 0;
    uint64_t checksum;
    Size *= 4;

	uint8_t Buffer[2];
	uint32_t posBuf;

	checksum = CheckSum((uint32_t)MemoryAddr + (missalignement & 0xf), Size - ((missalignement >> 16) & 0xF), InitVal);

	while (Size>VerifiedData)
	{
		flash_ReadMemory(MemoryAddr+VerifiedData, 2, Buffer);

		posBuf=0;
		while ((Size>VerifiedData) && (posBuf<1024)) {
			if (Buffer[posBuf] != *((uint8_t*)RAMBufferAddr+VerifiedData))
			{
				__set_PRIMASK(1); //disable interrupts
				return ((checksum<<32) + MemoryAddr+VerifiedData);
			}
			posBuf++;
			VerifiedData++;
		}
	}
	__set_PRIMASK(1); //disable interrupts
	return (checksum<<32);
}

And other read, write, etc. functions are in "Loader_Src.c". But name of other functions are not in .LD file. 

Could you explain this routine?

Best regards.

[KDJEM.1]

Hello @erkanc ,

Please refer to these FAQs and follow the needed changes in the linker file:

• How to add your SPI flash into the STM32CubeProgrammer’s external loader Part 1
• How to add your spi flash into the STM32CubeProgrammer's External Loader Part 2

I hope this help you.

Kaouthar

[Mohammad MORADI ESFAHANIASL · Accepted solution]

Hello @erkanc ,

I can see @KDJEM.1 has already provided excellent resources. 
I just wanted to point out that in the STM32 ST-LINK utility software description document, in section 3.9, there are some details about developing a customized external loader that might help you.  

[erkanc]

Thank you @Mohammad MORADI ESFAHANIASL for document.

Thank you @KDJEM.1. 

I understood how to generate custom external loader. I use following example;

https://www.youtube.com/watch?v=KlG2doCkREM

Thank you Mauro De Vecchi - Bluewat.

I strive 3 weeks. Finally, I succeeded. 

---

I am going to share a document for this subject in Turkish language after apprehend well. 

You can follow on my website and on this community.

www.elektrocavus.com

[Tesla DeLorean]

KEEP() is the method to ensure entry points to the "DLL" are retained, and not dead code eliminated by the Linker because nothing internally calls them.

https://github.com/cturvey/stm32extldr/blob/main/ExternalLoader_G4.ld#L42

[Mohammad MORADI ESFAHANIASL]

I'm very glad to hear you managed to make one :grinning_face:

Well done!