4.2. FreeRTOS¶

4.2.1. Introduction¶

FreeRTOS is a market-leading real-time operating system (RTOS) for microcontrollers and small microprocessors. Distributed freely under the MIT open source license, FreeRTOS includes a kernel and a growing set of libraries suitable for use across all industry sectors. FreeRTOS is built with an emphasis on reliability and ease of use.

PDK supports FreeRTOS on R5F, C66x, C7x CPUs for J721E. OSAL support and PDK Drivers running with FreeRTOS are available in this release.

FreeRTOS is not supported on A72 core.

4.2.2. Features Supported¶

FreeRTOS Kernel 10.4.3
- Tasks, semaphores, mutex, queues, timers, list, heap, event groups
- preemptive priority-based scheduler
- static and/or dynamic memory allocation Mode
In order to keep the PDK drivers/examples OS agnostic, additionally below OSAL modules are implemented to call FreeRTOS APIs underneath:-
- Clock, Task, Semaphore, Event, Mailbox, Mutex, Queue, Cache, HW Interrupts, HW Timers, Cycleprofiler, Heap, Load.

4.2.3. Features Not Supported¶

Co-routines, stream buffer are not enabled and compiled by default. Users can add these to the FreeRTOS config and makefile if they want to use these features.
Tickless IDLE mode
Task level memory protection wrapper
On R5F, nested interrupts are not supported.
HW Interrupt and SW Interrupt Load measurements are not supported.

4.2.4. Important files and directory structure¶

FreeRTOS source is distributed along with PDK and given below are some important files and folders related to FreeRTOS.

${PDK_INSTALL_PATH}/packages/ti/kernel
│
├────────────────────────────────── freertos
│                                    ├────── FreeRTOS-LTS   <= FreeRTOS Kernel source code. PDK simply clones the code from
│                                    │                         FreeRTOS Github and does not modify anything in this folder
│                                    │
│                                    ├────── config         <= FreeRTOS configuration header files for different SOCs and CPUs
│                                    │
│                                    └────── portable       <= FreeRTOS porting related files for supported cores
│
├────────────────────────────────── lib                     <= FreeRTOS library to link against. Linking to the library in this path
│                                                              enables the application to operate in FreeRTOS mode
│
└────────────────────────────────── test/freertos           <= FreeRTOS Examples and Unit Test

${PDK_INSTALL_PATH}/packages/ti/osal                        <= APIs to access FreeRTOS features in a OS agnostic way
│
└────────────────────────────────── lib/freertos            <= OSAL FreeRTOS library to link against. Linking to the library in this path
                                                               enables the application to use OSAL APIs which will operate in FreeRTOS mode

4.2.5. FreeRTOS Examples¶

Example	Application Name	Description	Cores Supported
FreeRTOS Task Switch	freertos_test_task_switch	The FreeRTOS Task Switch Example test performs the following: 1. switch between ping and pong tasks using semaphores 2. switch between ping and pong tasks using direct-to-task notifications 3. switch from ping task to ISR to pong task and back to ping task using semaphores, here there is a task switch	mcu1_0, mcu1_1, mcu2_0, mcu2_1, mcu3_0, mcu3_1, c66xdsp_1, c66xdsp_2, c7x_1
FreeRTOS Unit Test	freertos_test_ut	The FreeRTOS Unit Test performs the following: 1. switch between ping and pong tasks using semaphores 2. switch between ping and pong tasks using direct-to-task notifications 3. just invoke the task switch logic (Task Yield) without any semaphores or direct-to-task notifications 4. switch from ping to ISR and back to the same task using semaphores, here there is no task switch 5. switch from ping to ISR and back to the same task using direct-to-task notify, here there is no task switch 6. switch from ping task to ISR to pong task and back to ping task using semaphores, here there is a task switch 7. switch from ping task to ISR to pong task and back to ping task using direct-to-task notify, here there is a task switch 8. switch between ping and pong tasks and do float operations in between 9. Test TaskDelay	mcu1_0, mcu1_1, mcu2_0, mcu2_1, mcu3_0, mcu3_1, c66xdsp_1, c66xdsp_2, c7x_1

4.2.6. FreeRTOS Usage and Migration Guidelines¶

See FreeRTOS Usage and Migration Guidelines for FreeRTOS migration & usage guidelines and comparison to SysBIOS.

4.2.7. FreeRTOS with Real-time Object View (ROV)¶

Real-time Object View (ROV) in CCS IDE for FreeRTOS is available for R5F, C66x cores.

See FreeRTOS Real-time Object View (ROV) for instructions related to using Real-time Object View (ROV) with FreeRTOS.

4.2.8. Additional references¶

Document Description	Weblink
Easy to read FreeRTOS book	https://www.freertos.org/Documentation/RTOS_book.html
FreeRTOS user docs	https://www.freertos.org/features.html
User API reference	https://www.freertos.org/a00106.html
FreeRTOS core kernel source code	https://github.com/FreeRTOS/FreeRTOS-Kernel
FreeRTOS core kernel example source code	https://github.com/FreeRTOS/FreeRTOS/tree/master/FreeRTOS
Additional FreeRTOS.org maintained libraries (POSIX, TCP, Filesystem, …)	https://www.freertos.org/FreeRTOS-Labs/index.html
	https://www.freertos.org/FreeRTOS-Plus/index.html
	https://github.com/FreeRTOS