How to use DTCMRAM in stm32h743

[ykn]

Hi All,

I want to use DTCRAM in stm32cubeide, the controller i used is stm32h743, earlier I

Used RAM_D2. shifting from RAM_D2 to DTCRAM is possible but both i cant use,

please guide me,

 

/DISCARD/ :
 {
 libc.a ( * )
 libm.a ( * )
 libgcc.a ( * )
 }
 .RAMD2buffers(NOLOAD) : {
 . = ALIGN(4);
 *(.buffers*)
 } > DTCMRAM
 
.bssDTCMRAM(NOLOAD) : {
 . = ALIGN(4);
 *(.buffersDT*)
 } > RAM_D2
 
 .ARM.attributes 0 : { *(.ARM.attributes) }

the above code is added to linker file,

//__attribute__ ((section(".buffers"), used))
char rData[BUF_SIZE];// Read data
__attribute__ ((section(".buffers"), used))
uint32_t DMA_ADC1[ADC1_Size];
__attribute__ ((section(".buffers"), used))
uint32_t DMA_ADC2[ADC2_Size];
__attribute__ ((section(".buffers"), used))
uint32_t DMA_ADC3[ADC3_Size];
__attribute__ ((section(".buffersDT")))
uint32_t DMA_ADC3_dummy[ADC3_Size];

 

this code added to main file, 

thanking you

[Pavel A.]

DTCM (a.k.a. tightly core-coupled) memories are not accessible by peripherals DMA. That's is why they are very fast, and also don't work with DMA. Now you're informed.

 

[ykn]

Ok, what if I want to use it for general variable other than DMA, what should be the syantax.i tried the above, but the memory analyzer not showing DTCMRAM.

[mƎALLEm]

From your code I understand that you need to access DTCM with a general purpose DMA (DMA1 or DMA2) which is not possible. These masters don't have access to DTCM RAM. You need to use MDMA for this.

 

[ykn]

Can you provide me the syntaxes or link for DTCMRAM for general variable.

[Pavel A.]

Your syntax looks ok. The problem is something else.

 

[AScha.3]

Hi,

no problem, to use all ram areas, just write it in linker file:

 /* Initialized data sections into "RAM_D1" Ram type memory */
 .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 */
 
 } >DTCMRAM AT> FLASH /* war >RAM_D1 AT> FLASH */

 /* Uninitialized data section into "RAM_D1" Ram type memory */
 . = ALIGN(4);
 .bss :
 {
 /* This is used by the startup in order to initialize the .bss section */
 _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;
 } >DTCMRAM				/* war >RAM_D1 */

 /* User_heap_stack section, used to check that there is enough "RAM_D1" Ram type memory left */
 ._user_heap_stack :
 {
 . = ALIGN(8);
 PROVIDE ( end = . );
 PROVIDE ( _end = . );
 . = . + _Min_Heap_Size;
 . = . + _Min_Stack_Size;
 . = ALIGN(8);
 } >DTCMRAM

 .RAM_D1_sec :					/* (NOLOAD) <- keine initialisierung */ 
 {
 	. = ALIGN(32);
 *(.RAM_D1_section) 
 . = ALIGN(32);
 } >RAM_D1

so stack and variables in DTCMRAM .

Just where we need DMA, this needs to be in "normal" ram area , tell it the compiler/linker in main.c :

__attribute__((section(".RAM_D1_section"))) uint8_t inbuf[4096*8] __attribute__ ((aligned (32)));			// 32K file input buffer
__attribute__((section(".RAM_D1_section"))) int32_t out_buf[4096*4], rc, iPitch=40, i, j;					// 16kB -> Radio
uint16_t peak_val, myfilter=0,source=0;

-> inbuf+outbuf , i, j : in ram_D1 , peak_val etc. in  DTCMRAM .

 

[Pavel A.]

> but what about bufferDT

Pattern *(.buffers*)  is before *(.buffersDT*) in the script, so it captures the latter. Move the 2nd section up above the 1st one.

 

[ykn]

 

 /DISCARD/ :
 {
 libc.a ( * )
 libm.a ( * )
 libgcc.a ( * )
 }
 
 .bssDTCMRAM(NOLOAD) : {
 . = ALIGN(4);
 *(.buffersDT*)
 } > DTCMRAM
 
 .RAMD2buffers(NOLOAD) : {
 . = ALIGN(4);
 *(.buffers*)
 } > RAM_D2

 

In this way, Now no initialization in DTCMRAM:frowning_face:

[Pavel A.]

> Now no initialization in DTCMRAM

Because in this line only "used" is missing )) This variable likely is not referenced.

__attribute__ ((section(".buffersDT")))

Please read the ld documentation, take your time.

[Tesla DeLorean]

Pick less ambiguous patterns.

File is processed in-order, variables need to be used or dead-code elimination will discard them