ARM Cortex-M33 (ARMv8-M) Keil Simulator Demo
Using Keil uVision IDE
[RTOS Ports]

This page documents a pre-configured FreeRTOS project that targets the Keil uVision ARM Cortex-M33 Simulator and uses the armclang compiler to build the FreeRTOS ARMv8-M GCC port. The project demonstrates using the ARM Cortex-M33 TrustZone and the ARM Cortex-M33 Memory Protection Unit (MPU).

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IMPORTANT! Notes on using the FreeRTOS ARM Cortex-M33 port

Please read all the following points before using this RTOS port.

1. Source Code Organization
2. The Demo Application
3. Building and Running the RTOS Demo Application
4. RTOS Configuration and Usage Details

Also see the FAQ My application does not run, what could be wrong?, the page that describes running FreeRTOS on ARMv8-M cores, and the page that describes setting ARM Cortex-M interrupt priorities for use with FreeRTOS.

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Source Code Organization

The FreeRTOS zip file download contains the source code for all the FreeRTOS ports, and every demo application. That means it contains many more files than are required to use the FreeRTOS ARMv8-M Cortex-M33 port. See the Source Code Organization page for information on the zip file's directory structure.

The project file for this demo is located in the FreeRTOS/Demo/CORTEX_MPU_M33F_Simulator_Keil_GCC directory and is named FreeRTOSDemo.uvmpw. This Keil multi-project workspace contains two projects - one for the secure side of the ARM Cortex-M33 core, and one for the non-secure side. The FreeRTOS ARMv8-M Cortex-M33 port files compiled in these two projects are organized as follows:

• Port files compiled in the secure project are in the FreeRTOS/Source/portable/GCC/ARM_CM33/secure directory.
• Port files compiled in the non-secure project are in the FreeRTOS/Source/portable/GCC/ARM_CM33/non_secure directory.

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The Demo Application

The project includes two demos:

1. TrustZone Demo
2. Memory Protection Unit (MPU) Demo

TrustZone Demo

The TrustZone demo demonstrates how to export functions from the secure side of the ARM Cortex-M33 core, and how to call them from RTOS tasks on the non-secure side.

• NonSecure Callable Function:

  The following function is exported from the secure side and is marked as non-secure callable:

  secureportNON_SECURE_CALLABLE uint32_t NSCFunction( Callback_t pxCallback )

  Note the use of secureportNON_SECURE_CALLABLE macro to mark the function as non-secure callable. This function accepts a callback as argument. It first invokes the callback function supplied as argument and then increments a secure side counter. The incremented value of the secure side counter is returned to the caller.
• NonSecure Callback:

  The following function is implemented on the non-secure side and is passed to the above mentioned non-secure callable function as argument:

  void prvCallback( void )

  This function increments a non-secure counter.
• Secure Calling Task:

  An un-privileged non-secure task is created using the xTaskCreateRestricted() API. This task first calls portALLOCATE_SECURE_CONTEXT to allocate itself a secure context - any non-secure task which wants to call a function exported from the secure side must allocate itself a secure context by calling portALLOCATE_SECURE_CONTEXT.

  The task then calls the secure side function and passes the non-secure callback as the argument. The non-secure counter is incremented in the callback and the secure counter is incremented in the secure function. Therefore, both the counters must be incremented after the call to the secure function is complete - this is ensured using configASSERT(). The task sleeps for one second and then repeats the same.

Memory Protection Unit (MPU) Demo

The MPU demo demonstrates how to use MPU to grant a task different permissions to various memory regions. The MPU demo consists of the following two tasks:

• RW Task:

  The RW task has Read-Write access to a shared region of memory (namely ucSharedMemory).

• RO Task:

  The RO task has Read-Only access to the same shared region of memory (namely ucSharedMemory). This task tries to write to the shared memory and since it has read only permission to the shared memory, it results in a memory fault. The fault handler checks if it is the expected fault from the RO task and if so, it recovers gracefully by incrementing the Program Counter to the next statement.

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Building and Running the RTOS Demo Application

1. Double click the FreeRTOS/Demo/CORTEX_MPU_M33F_Simulator_Keil_GCC/FreeRTOSDemo.uvmpw file to open it in the Keil uVision IDE. The Keil multi-project workspace FreeRTOSDemo.uvmpw contains a secure project (FreeRTOSDemo_s) and a non-secure project (FreeRTOSDemo_ns).

2. Set the secure project as active by right clicking on "Project: FreeRTOSDemo_s" and selecting "Set as Active Project".

   
   Keil uVision IDE - Set Secure Project Active. Click to enlarge.

3. Build the secure project by clicking "Project --> Build 'FreeRTOSDemo_s (FVP Simulation Model)'".

   
   Keil uVision IDE - Build Secure Project. Click to enlarge.

4. Set the non-secure project as active by right clicking on "Project: FreeRTOSDemo_ns" and selecting "Set as Active Project".

   
   Keil uVision IDE - Set Non-Secure Project Active. Click to enlarge.

5. Build the non-secure project by clicking "Project --> Build 'FreeRTOSDemo_ns (FVP Simulation Model)'".

   
   Keil uVision IDE - Build Non-Secure Project. Click to enlarge.

6. Start the Debug Session by clicking "Debug -> Start/Stop Debug Session".

   
   Keil uVision IDE - Start Debug Session. Click to enlarge.

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RTOS Configuration and Usage Details

Also see the page that describes running FreeRTOS on ARMv8-M cores, and the page that describes setting ARM Cortex-M interrupt priorities for use with FreeRTOS.

• Configuration items specific to this demo are contained in FreeRTOS/Demo/CORTEX_MPU_M33F_Simulator_Keil_GCC/Config/FreeRTOSConfig.h. The constants defined in that file can be edited to suit your application. The following configuration options are specific to the ARM Cortex-M33 port:

  • configENABLE_MPU - Enable/Disable Memory Protection Unit (MPU).
  • configENABLE_FPU - Enable/Disable Floating Point Unit (FPU).
  • configENABLE_TRUSTZONE - Enable/Disable TrustZone.

• If you want to run FreeRTOS with TrustZone disabled, set configENABLE_TRUSTZONE to 0 in your FreeRTOSConfig.h and use the FreeRTOS port files in the FreeRTOS/Source/portable/GCC/ARM_CM33_NTZ directory.

• If you want to run FreeRTOS on the secure side, set configENABLE_TRUSTZONE to 0 and configRUN_FREERTOS_SECURE_ONLY to 1 in your FreeRTOSConfig.h and use the FreeRTOS port files in the FreeRTOS/Source/portable/GCC/ARM_CM33_NTZ directory.

• Source/Portable/MemMang/heap_4.c is included in the 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.

• vPortEndScheduler() has not been implemented.