The FreeRTOS kernel is now an MIT licensed AWS open source project, and these pages are being updated accordingly.

Quality RTOS & Embedded Software About   Contact   Support   FAQ   Download Menu      Quick Start Supported MCUs PDF Books Trace Tools Ecosystem Quick Start Guide Support Forum ⇓ Download Source ⇓ FreeRTOS+ Ecosystem  FreeRTOS+TCP:  Thread safe TCP/IP stack  SafeRTOS:  TUV certified RTOS  OpenRTOS:  Commercial Licensed RTOS  Fail Safe File System:  Ensures data integrity  FreeRTOS BSPs:  3rd party driver packages  Trace & Visualisation:  Tracealyzer for FreeRTOS  CLI:  Command line interface  WolfSSL SSL / TLS:  Networking security protocols  RTOS Training:  Delivered online or on-site  IO:  read(), write(), ioctl() interface FreeRTOS+ Lab Projects  FreeRTOS+POSIX:  POSIX threading API  FreeRTOS+FAT:  Thread aware file system Hint: Use the tree menu to navigate groups of related pages   Restoring the Context [RTOS Implementation Building Blocks] The RTOS macro portRESTORE_CONTEXT() is the reverse of portSAVE_CONTEXT(). The context of the task being resumed was previously stored in the tasks stack. The real time kernel retrieves the stack pointer for the task then POP's the context back into the correct processor registers. #define portRESTORE_CONTEXT() \ asm volatile ( "lds r26, pxCurrentTCB \n\t" \ (1) "lds r27, pxCurrentTCB + 1 \n\t" \ (2) "ld r28, x+ \n\t" \ "out __SP_L__, r28 \n\t" \ (3) "ld r29, x+ \n\t" \ "out __SP_H__, r29 \n\t" \ (4) "pop r31 \n\t" \ "pop r30 \n\t" \ : : : "pop r1 \n\t" \ "pop r0 \n\t" \ (5) "out __SREG__, r0 \n\t" \ (6) "pop r0 \n\t" \ (7) ); Referring to the code above: The FreeRTOS pxCurrentTCB variable holds the address from where the tasks stack pointer can be retrieved. This is loaded into the X register (1 and 2). The stack pointer for the task being resumed is loaded into the AVR stack pointer, first the low byte (3), then the high nibble (4). The processor registers are then popped from the stack in reverse numerical order, down to R1. The status register stored on the stack between registers R1 and R0, so is restored (6) before R0 (7). Next: RTOS Implementation - Putting It All Together [ Back to the top ]    [ About FreeRTOS ]    [ Privacy ]    [ Sitemap ]    [ ] Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.

Latest News NXP tweet showing LPC5500 (ARMv8-M Cortex-M33) running FreeRTOS. Meet Richard Barry and learn about running FreeRTOS on RISC-V at FOSDEM 2019 Version 10.1.1 of the FreeRTOS kernel is available for immediate download. MIT licensed. View a recording of the "OTA Update Security and Reliability" webinar, presented by TI and AWS. Careers FreeRTOS and other embedded software careers at AWS. FreeRTOS Partners