Posted on March 30, 2016 at 15:16
Hello,
I am fairly new to embedded development and I am trying to setup a project (using Eclipse GNU ARM environment) to use ITCM and DTCM on a STM32F7 Discovery board.
It seems the default linker script already uses DTCM by defining a global RAM section starting at the DTCM address 0x20000000 (although I would like to decide which data to put in the DTCM as my data is larger than the DTCM). But, more importantly, I am having trouble enabling ITCM. I have looked at the ''Performance test'' example & notes as well as the template examples from the STM32F7 firmware, plus forum pages about the subject... but it seems I couldn't find the correct answer, or at least it is not working for me. I have also looked at other parties linker scripts and tried applying them to the STM32F7, with no luck.
Here is what I would ideally like to achieve:
1) put specific part of the code (or an entire object functions) into ITCM
2) put specific data into the DTCM
I added the following section to the mem.ld linker script
ITCM_RAM(xr): ORIGIN = 0x00000000, LENGTH = 16K
Then, I understand there are two ways of putting code into the ITCM:
1) by including the entire .o code into a ''section'' allocated to the ITCM
.code_TCM 0x00000000:
AT ( _itcm_lma )
{
_sitcm = .;
myobject.o (.text.*)
myobject.o (.rodata)
_eitcm = .;
} > ITCM_RAM
Also adding this to the _startup.c method, right before the main(..) call (I was not sure yet if the _startup.c code was handling this situation, and I assume this is not a problem to do perform the copy again):
/* copy code_TCM from flash to ITCM */
volatile char *dst = &_sitcm;
volatile char *src = &_itcm_lma;
while(dst < &_eitcm){
*dst++ = *src++;
}
2) by tagging methods using the __attribute__((section(''.code_TCM''))) e.g.
void __attribute((section(''.code_TCM''))) Run() {
/*
code here
*/
}
And the following linker script:
.code_TCM :
{
. = ALIGN(4);
*(.code_TCM) /* .section_name section */
*(.code_TCM*) /* .section_name* sub-sections if any */
. = ALIGN(4);
} >ITCM_RAM AT> FLASH
When adding the object into the ITCM section (method 1), I am having linking errors with duplicate definitions ...
If I tag a method into the ITCM (method 2) and try to call this method, I get a hard fault ...
I am currently testing this using C methods but my engine is mostly written in C++ so my first question is: can I use C++ classes and put their member functions into ITCM?
In the ideal case, would somebody have an example of a linker script that allows __attribute__ use to put data/code into DTCM/ITCM? Any help is greatly appreciated !!
Thank you
#stm32f7-dtcm-itcm
