topic Re: FRDM-K64F Context switching MSP & PSP in Kinetis Microcontrollers

FRDM-K64F Context switching MSP & PSP

luisgarabo — Thu, 12 Apr 2018 17:58:54 GMT

Hi,

Do you have an example of FRDM-K64F Context switching MSP & PSP?

Thanks for your help,

Re: FRDM-K64F Context switching MSP & PSP

mjbcswitzerland — Thu, 12 Apr 2018 23:55:04 GMT

You can study the FreeRTOS file /source/portable/GCC/ARM_MC4F/port.c to get some examples of such context switching.

Regards

Mark

uTasker developer and supporter (+5'000 hours experience on +60 Kinetis derivatives in +80 product developments)
Kinetis: http://www.utasker.com/kinetis.html

Re: FRDM-K64F Context switching MSP & PSP

miduo — Fri, 13 Apr 2018 05:31:16 GMT

Hi,

Please make reference the MQX RTCS code, where in boot.s, the active stack pointer is set to PSP (set bit 1 of the CONTROL register). Then no need do any manipulation of this bit. Cortex m4 itself automatically switches the active stack pointer to MSP in handler mode and switches back to PSP with exception return.

Here is the stack pointer switch code at <boot.s>

	/* Prepare process stack pointer */
	mrs r0, MSP
	msr PSP, r0

	/* Switch to proccess stack (PSP) */
	mrs r0, CONTROL
	orr r0, r0, #2
	msr CONTROL, r0
	isb #15

Re: FRDM-K64F Context switching MSP & PSP

CCandido — Fri, 20 Apr 2018 00:50:52 GMT

Hi Luis,

I tested it code not run, you can test.

stm32f4 - scheduler and stack - Electrical Engineering Stack Exchange

thanks,

Carlos.

Re: FRDM-K64F Context switching MSP & PSP

luisgarabo — Fri, 20 Apr 2018 21:16:36 GMT

Thank you Carlos, Fang and Mark,

Your suggestions helped a lot. I implemented the code suggested by Carlos and I found that the priority for the PendSV call is set differently for the K64. I used the following:

NVIC_SetPriority(PendSV_IRQn, 0xF); // Set PendSV to lowest possible priority

It works great!

Thanks!

Luis