topic Re: Free RTOS heap memory changed from SRAM0 to DTCM in S32K

Free RTOS heap memory changed from SRAM0 to DTCM

Omkar9903 — Fri, 17 Apr 2026 13:48:01 GMT

Hi,

I am using FreeRTOS with heap_1.c, and the configuration
configAPPLICATION_ALLOCATED_HEAP = 1 is enabled.

I have allocated the FreeRTOS heap in DTCM RAM from main.c as shown below:

uint8_t ucHeap[ configTOTAL_HEAP_SIZE ]

__attribute__((section(".my_heap")));

In the linker script, I have mapped the heap section to DTCM memory as follows:

/* Heap section */

/* Data tightly coupled memory (D-TCM) */

dtcm (rw) : ORIGIN = 0x20000000, LENGTH = 0x1F000 /* 124KB Data RAM */

stack_dtcm (rw) : ORIGIN = 0x2001F000, LENGTH = 0x1000 /* 4KB */

.bss_tcm_data (NOLOAD) :

{

. = ALIGN(4);

__dtcm_bss_start__ = .;

*(.dtcm_bss*)

. = ALIGN(4);

__dtcm_bss_end__ = .;

*(.my_heap)

} > dtcm

.heap (NOLOAD) :

{

. = ALIGN(4);

_end = .;

end = .;

_heap_start = .;

. += HEAP_SIZE;

_heap_end = .;

} > dtcm

.my_heap (NOLOAD) :

{

*(.my_heap)

} > dtcm

The .map file confirms that the heap memory has been placed in DTCM.
However, after this change, FreeRTOS is not functioning correctly.

Could you please help review this setup and advise on what might be missing or incorrect?

Re: Free RTOS heap memory changed from SRAM0 to DTCM

danielmartynek — Mon, 20 Apr 2026 10:37:38 GMT

Hi @Omkar9903,

Could you please clarify what you mean by “FreeRTOS is not functioning correctly”?
For example, does the scheduler fail to start, do tasks not run, or are you encountering a HardFault?
Also, can you ensure that the .my_heap section is aligned in the same way as the default .heap section.

Finally, please provide the following details so the issue can be analyzed accurately:

MCU variant
RTD version
FreeRTOS RTD extension version

BR, Daniel

Re: Free RTOS heap memory changed from SRAM0 to DTCM

Omkar9903 — Mon, 20 Apr 2026 12:14:47 GMT

Hi @danielmartynek ,

I am using s32k341 microcontroller with RTD version 5.0.0 and RTOS version FreeRTOS Kernel V10.5.0.

The issue is observed that we are getting hard fault from clock init function i.e "Clock_Ip_SetWaitStates"

I have declared the heap array in main.c as follows:

UNSIGNED8 ucHeap[8712] __attribute__((section(".dtcm_bss")));

I have verified in the MAP file that ucHeap is correctly allocated in DTCM memory.

I am attaching my linker file for review.
Please let me know if anything is missing or incorrectly configured.

snapshot of map file :

note main.c is renamed as sid.c

Thanks.

Re: Free RTOS heap memory changed from SRAM0 to DTCM

danielmartynek — Wed, 22 Apr 2026 06:58:07 GMT

Hi @Omkar9903,

How is portBYTE_ALIGNMENT defined in portmacro.h

https://forums.freertos.org/t/memory-alignment-in-heap-1-c-file/13355

The heap should be aligned to that number of bytes.

Regarding the fault exception, try to find more information about it:

https://community.nxp.com/t5/S32K-Knowledge-Base/Example-S32K312-HARDFAULT-Handling-Interrupt-DS3-5-RTD300/ta-p/1806259

https://community.nxp.com/t5/S32K-Knowledge-Base/How-To-Debug-A-Fault-Exception-On-ARM-Cortex-M-V7M-MCU-S32K3XX/ta-p/1595570

https://community.nxp.com/t5/S32K-Knowledge-Base/Fault-handling-on-S32K14x/ta-p/1114447

BR, Daniel