Kernel Configuration

The FreeRTOS kernel is configured by FreeRTOSConfig.h file which can be found in {SDK_INSTALL_DIR}\kernel\freertos\builds\{DEVICE}\release\pregenerated_configuration, you can change the configuration file so that the kernel will be tailored to your application. For more information about kernel configuration, please see FreeRTOS Kernel Configuration Overview.

In the SimpleLink Low Power F3 SDK, all FreeRTOS application routines are abstracted using the following:

  • A POSIX layer, which was designed for use with this SimpleLink Low Power F3 SDK

  • A Driver Porting Layer (DPL) for use by the TI Drivers

You can find example FreeRTOS projects that use the SimpleLink Low Power F3 SDK in the examples/rtos/ folder for all supported IDEs.

No native FreeRTOS examples are provided in this SimpleLink Low Power F3 SDK. If you want to use the native FreeRTOS routines without the abstractions provided by the SimpleLink Low Power F3 SDK, documentation is provided on the FreeRTOS website.

POSIX Support

Portable Operating System Interface (POSIX) is an IEEE industry API standard for OS compatibility. The SimpleLink Low Power F3 SDK provides support for POSIX APIs on top of FreeRTOS (as it does for TI-RTOS7). For a more detailed description of the POSIX support in the SimpleLink Low Power F3 SDK, please refer to the POSIX Overview Workshop

Driver Porting Layer (DPL)

The TI Drivers (e.g. UART2, I2C, Power Management, etc.) are written to be used with the Driver Porting Layer (DPL). The SimpleLink Low Power F3 SDK includes a DPL implementation for both FreeRTOS, TI-RTOS7 and no RTOS.

../_images/driver_levels_dpl.png

Using FreeRTOS with CCS

In order to use FreeRTOS within CCS, you must specify the location of the FreeRTOS installation. To do this, follow these steps:

  1. In CCS, choose Window → Preferences from the menus.

  2. Select the General → Workspace → Linked Resource category.

  3. Click New and add a link with the following settings.

    • Name: FREERTOS_INSTALL_DIR

    • Value: The location of your FreeRTOS installation

      ../_images/freertos_install_dir.png

These steps only need to be performed once per CCS workspace that you create.

FreeRTOS vs. TI-RTOS7 modules

The application and the ICall layer communicate using events to call the OS and made context switch. The table below shows the modules that are used by TI-RTOS7 in a typical example flow, at the same time explains which modules are used by FreeRTOS.

Table 4. Replacing modules that supports FreeRTOS in place of TI-RTOS7 modules

Example flow

TI-RTOS7 modules

FreeRTOS modules

1. Application Thread Listen (pend) on event number

TI-RTOS7 Semaphore/Event

SemaphoreP (used through DPL layer) and mq_send / mq_receive Blocking Mqueue (POSIX queues)

2. Stack Thread Doing whatever he asked to do by the app called

TI-RTOS7 Timers

TimersP (used through DPL layer)

3. Stack Thread Push a message (or number of messages) into the queue and post an event Queue

TI-RTOS7 utility Queue

mq_send / mq_receive NON-Blocking Mqueue (POSIX queues)

4. Application Thread OS wakes the application thread and the application pulls the message from the Non-OS queue

TI-RTOS7 utility Queue

mq_send / mq_receive NON-Blocking Mqueue (POSIX queues)

5. Application Thread Listen (pend) on event number - cycle has completed

TI-RTOS7 event

mq_send / mq_receive Blocking Mqueue (POSIX queues)

icall_POSIX

The file ICall_POSIX is based on POSIX, DPL and FreeRTOS bare APIs calls. This implementation should allow us to support different Operating Systems if required. In order to do this, all the #ifdef FreeRTOS on the current ICall_POSIX could be changed to support a different OS.

Here are some of the places where these defines are used (icall_POSIX.c):

Listing 1. ical_POSIX.c - Includes
#ifdef FREERTOS
#include <FreeRTOS.h>
#include <task.h>
#endif
Listing 2. ical_POSIX.c - ICall_taskSelf()
Task_Handle ICall_taskSelf(void)
{
  Task_Handle task = NULL;
#ifdef FREERTOS
  task = (Task_Handle) xTaskGetCurrentTaskHandle();
#else
  task = <handler need to be returned according to the chosen OS>;
#endif // FREERTOS
  return (task);
}
Listing 3. ical_POSIX.c
#ifndef FREERTOS
#if defined(HEAPMGR_CONFIG) && ((HEAPMGR_CONFIG == 0) || (HEAPMGR_CONFIG == 0x80))
#include <rtos_heaposal.h>
#elif defined(HEAPMGR_CONFIG) && ( (HEAPMGR_CONFIG == 1) || (HEAPMGR_CONFIG == 0x81))
#include <rtos_heapmem.h>
#elif defined(HEAPMGR_CONFIG) && ( (HEAPMGR_CONFIG == 2) || (HEAPMGR_CONFIG == 0x82))
#include <rtos_heaptrack.h>
#else
static ICall_CSState ICall_heapCSState;
#include <rtos_heaposal.h>
#endif
#endif // !FREERTOS