AN4329 Copy function to RAM and execute from RAM (frdm-k64 example project)

[jacobjennings]

Hello,

Based on AN-4329, I assembled a test project (attached) for the FRDM-K64F which attempts to copy a function to RAM and run it, but I am getting a fault when attempting to call the function. The Source and Destiny variables seem to be in the correct ranges in copyToMyRam, but the call fails.

AN4329 - NXP

Note changes in the ProcessorExpert.ld file, and main.c

Any advice is appreciated! It seems very close.

Thanks,

Jake

Original Attachment has been moved to: test-run-from-memory-frdm-k64f.zip

[jacobjennings]

I got things working and wrote up a summary here:

Jake Jennings on Twitter: "Leverage the GNU ARM linker to relocate and execute code from RAM https:/...

Jacob Jennings Tech • Leverage the GNU ARM linker to relocate and...

Code here: GitHub - jacobjennings/gnu-arm-execute-from-ram-example: Demonstrate linker file and process for sel... 

[mjbcswitzerland]

Hi

Make sure that you are creating a thumb-comform copy of the code in SRAM since if it i not correctly aligned it will fail.

Below is an example where fnFlashRoutine() is a small subroutine to be copied to SRAM and later executed by calling fnRAM_code()

Regards

Mark

	#define PROG_WORD_SIZE 30	// adequate space for the small program
	int i = 0;
	unsigned char *ptrThumb2 = (unsigned char *)fnFlashRoutine;
	static unsigned short usProgSpace[PROG_WORD_SIZE] = {0};	// make space for the routine on stack (this will have an even boundary)

	ptrThumb2 =  (unsigned char *)(((CAST_POINTER_ARITHMETIC)ptrThumb2) & ~0x1); // thumb 2 address
	while (i < PROG_WORD_SIZE) {	// copy program to SRAM
	usProgSpace[i++] = *(unsigned short *)ptrThumb2;
	ptrThumb2 += sizeof (unsigned short);
	}
	ptrThumb2 = (unsigned char *)usProgSpace;
	ptrThumb2++;	// create a thumb 2 call
	fnRAM_code = (void(*)(volatile unsigned char *))(ptrThumb2);