Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Real time embedded FreeRTOS mailing list 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem TCP & FAT Training




Loading

Suspend to SRAM w/ FreeRTOS?

Posted by kenkyee on September 20, 2013

I'm wondering if FreeRTOS can do "suspend to SRAM" for a deeper sleep state than Tickless mode? It would save the configuration state of all drivers and any system state to a secondary memory SRAM chip (not DRAM so that it doesn't need any refreshing) and won't wake up until a timer and/or RTC and/or external (pins/serial port, usb port) interrupt. Then after the interrupt causes it to come back, it restores everything and comes out of Idle.

Most Cortex chips support this kind of ultra low power mode, but sadly don't have anything that helps you save/restore system/peripheral state to memory :-(


Suspend to SRAM w/ FreeRTOS?

Posted by richardbarry on September 21, 2013

The tickless mode can currently use any sleep state that retains the RAM and CPU registers. For example, the SAM4L demo (http://www.freertos.org/AtmelSAM4L-EKLowPowerTick-lessRTOSDemo.html) uses an extreme low power state (measured at 3uA) that is the lowest this specialist low power chip can manage without loosing CPU register values. Once the CPU registers are gone then you are into the sort of scheme discussed in this thread: http://www.freertos.org/FreeRTOSSupportForumArchive/September2013/freertosresumingFreeRTOSstatefromexternalSRAM_8679833.html

and I'm not sure if keeping the external SRAM powered to take another micro amp off the power consumed by the CPU is going to same much.

Regards.


Suspend to SRAM w/ FreeRTOS?

Posted by richard_damon on September 21, 2013

The low power modes that loose memory contents are NOT designed to be used by a Real Time application that "saves" all of the state then goes into this mode. The problem being that this can take a lot of time, and what ever is going to remember that state will be taking power (or be very slow).

These states are used for applications that know they aren't going to be needed for a while, to save a little bit of essential state, and turn the machine off except for a few critical I/O devices that can wake the system up, which the quickly "re-boots" the application, using the saved state information, and handles the request.

A generic operating system (like FreeRTOS) isn't going to know how to distill the current state down enough, that is really an application specific operation.


[ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ]




Copyright (C) 2004-2010 Richard Barry. Copyright (C) 2010-2016 Real Time Engineers Ltd.
Any and all data, files, source code, html content and documentation included in the FreeRTOSTM distribution or available on this site are the exclusive property of Real Time Engineers Ltd.. See the files license.txt (included in the distribution) and this copyright notice for more information. FreeRTOSTM and FreeRTOS.orgTM are trade marks of Real Time Engineers Ltd.

Latest News:

FreeRTOS V9.0.0 is now available for download.


Free TCP/IP and file system demos for the RTOS


Sponsored Links

⇓ Now With No Code Size Limit! ⇓
⇑ Free Download Without Registering ⇑


FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

Renesas Electronics Gold Alliance RTOS Partner.jpg

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers

Atmel RTOS partner supporting ARM Cortex-M3 and AVR32 microcontrollers

STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Xilinx Microblaze and Zynq partner

Silicon Labs low power RTOS partner

Altera RTOS partner for Nios II and Cortex-A9 SoC

Freescale Alliance RTOS Member supporting ARM and ColdFire microcontrollers

Infineon ARM Cortex-M microcontrollers

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

Cypress RTOS partner supporting ARM Cortex-M3

Fujitsu RTOS partner supporting ARM Cortex-M3 and FM3

Microsemi (previously Actel) RTOS partner supporting ARM Cortex-M3

Atollic Partner

IAR Partner

Keil ARM Partner

Embedded Artists