This page documents an application that demonstrates the use of FreeRTOS on a Renesas RL78 16-bit microcontroller. The demo is configured to run on the RL78/G13 Promotion Board (YRPBRL78G13), which is fitted with a R5F100LEA microcontroller. The R5F100LEA provides the software application with a little under 4K bytes of usable RAM, which is not enough for all the FreeRTOS features to be fully demonstrated in this single application. The RL78 range does, however, include parts with up to 32K bytes of RAM, some eight times more RAM than that available on the R5F100LEA. The R5F100LEA demo creates 13 tasks, 4 queues and two timers. Note: If this project fails to build then it is likely the version of IAR Embedded Workbench being used is too old. If this is the case, then it is also likely that the project file has been (silently) corrupted and will need to be restored to its original state before it can be built even with an updated IAR version.
IMPORTANT! Notes on using the Renesas RL78 RTOS portPlease read all the following points before using this RTOS port.See also the FAQ My application does not run, what could be wrong? Source Code OrganizationThe FreeRTOS download contains the source code for all the FreeRTOS ports, so contains many more files than used by this demo. See the Source Code Organization section for a description of the downloaded files and information on creating a new project.The IAR Embedded Workbench workspace for the Renesas RL78 Promo Board demo is called RTOSDemo.eww, and is located in the FreeRTOS\Demo\RL78_RL78G13_Promo_Board_IAR directory.
The Demo ApplicationDemo application hardware setupThe demo application makes use of an LED that is mounted directly onto the promo board hardware, so no additional hardware setup is required.
FunctionalityThis section describes the functionality of the RL78G13 demo. In all, thirteen tasks, four queues and two timers are used. Some of the tasks are from the set of 'standard demo' tasks. These are common to all FreeRTOS demos, so are not RL78 specific. They have no other purpose than to demonstrate use of the FreeRTOS API, and to test the core FreeRTOS functionality.The following demo specific tasks are created in addition to the standard demo tasks:
main.c also includes example stack overflow, idle, and malloc files hook functions. When executing correctly, the demo application will toggle the user LED every three seconds.
Building the demo application
Programming the microcontroller and debugging
Configuration and Usage DetailsRTOS port specific configurationConfiguration items specific to this demo are contained in FreeRTOS\Demo\RL78_RL78G13_Promo_Board_IAR\FreeRTOSConfig.h. The constants defined in this file can be edited to suit your application.There is also a constant that is specific to the Renesas RL78 port and demo:
Each port #defines 'BaseType_t' to equal the most efficient data type for that processor. This port defines BaseType_t to be of type short. Note that vPortEndScheduler() has not been implemented. Memory modelsThe FreeRTOS port will automatically switch between the near and far memory models, depending on the settings in the IAR project options. The port has been tested with two memory model combinations, which are:
Writing interrupt service routinesInterrupt service routines that cannot cause a context switch have no special requirements and can be written as described by the IAR compiler documentation.Often you will require an interrupt service routine to cause a context switch. For example a serial port character being received may unblock a high priority task that was blocked waiting for the character to arrive. If the unblocked task has a higher priority than the current task, then the ISR should return directly to the unblocked task. Limitations in the IAR inline assembler necessitate such interrupt service routines are entered using an assembly file wrapper. An example is provided below. First the assembly file wrapper. ; ISR_Support.h defines the portSAVE_CONTEXT and portRESTORE_CONTEXT ; macros. #include "ISR_Support.h" ; The wrapped implemented in the assembly file. PUBLIC vISRWrapper ; The portion of the handler that is implemented in an external C file. EXTERN vISRHandler ; Ensure the code segment is used. RSEG CODE:CODE ; The wrapper is the interrupt entry point. vISRWrapper: ; The ISR must start with a call to the portSAVE_CONTEXT() macro to save ; the context of the currently running task. portSAVE_CONTEXT ; Once the context is saved the C portion of the handler can be called. ; This is where the interrupting peripheral is actually serviced. call vISRHandler ; Finally the ISR must end with a call to portRESTORE_CONTEXT() followed by ; a reti instruction to return from the interrupt to whichever task is ; now the task selected to run (which may be different to the task that ; was running before the interrupt started). portRESTORE_CONTEXT reti ; The interrupt handler can be installed into the vector table in the same ;assembly file. ; Ensure the vector table segement is used. COMMON INTVEC:CODE:ROOT(1) ; Place a pointer to the asm wrapper at the correct index into the vector ; table. Note 56 is used is purely as an example. The correct vector ; number for the interrupt being installed must be used. ORG 56 DW vISRWrapper An example assembly file wrapper for an interrupt handler.
The C portion of the interrupt handler is just a standard C function. /* This standard C function is called from the assembly wrapper above. */ void vISRHandler( void ) { short sHigherPriorityTaskWoken = pdFALSE; /* Handler code goes here, for purposes of demonstration, assume at some point the hander calls xSemaphoreGiveFromISR().*/ xSemaphoreGiveFromISR( xSemaphore, &sHigherPriorityTaskWoken ); /* If giving the semaphore unblocked a task, and the unblocked task has a priority that is higher than the currently running task, then sHigherPriorityTaskWoken will have been set to pdTRUE. Passing a pdTRUE value to portYIELD_FROM_ISR() will cause this interrupt to return directly to the higher priority unblocked task. */ portYIELD_FROM_ISR( sHigherPriorityTaskWoken ); } The C portion of the example interrupt handler.
Resources used by the RTOS kernelThe RTOS kernel uses the interval timer to generate the RTOS tick. The function prvSetupTimerInterrupts() in FreeRTOS\Source\portable\IAR\RL78\port.c can be altered to use any convenient timer source.The RTOS kernel also requires exclusive use of the BRK software interrupt instruction. Compiler optionsAs with all the ports, it is essential that the correct compiler options are used. The best way to ensure this is to base your application on the provided demo application files.Memory allocationSource\Portable\MemMang\heap_1.c is included in the demo application project to provide the memory allocation required by the RTOS kernel. Please refer to the Memory Management section of the API documentation for full information.
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