# IoT Reference Integration for Arm Corstone-3xx with CMSIS-RTOS2

## Introduction

This reference integration demonstrates how to develop cloud connected
applications and update them securely by integrating
[CMSIS-FreeRTOS](https://arm-software.github.io/CMSIS-FreeRTOS/main/index.html)
([FreeRTOS kernel](https://www.freertos.org/RTOS.html) with a
[CMSIS-RTOSv2](https://arm-software.github.io/CMSIS_5/RTOS2/html/index.html) compatibility layer),
and utilizing hardware enforced security based on [Arm TrustZone (Armv8-M)](https://www.arm.com/architecture/learn-the-architecture/m-profile).

To utilize the hardware enforced security, this integration uses PSA Certified
reference implementation [Trusted Firmware-M](https://www.trustedfirmware.org/projects/tf-m/).
Trusted Firmware-M provides various Secure services such as Secure boot, Crypto, Secure Storage,
Attestation and Update services meeting [PSA Certified requirements](https://www.psacertified.org/blog/psa-certified-10-security-goals-explained/).

Developers and partners can use this integration as a starting point to build
CMSIS-FreeRTOS based software stack on top of Arm Cortex-M based
platforms. All the components are put together in a modular manner to make
porting of this integration across platforms easy.

## Architecture

The following diagram illustrates the architecture of the CMSIS-RTOS2 FRI project.

![diagram](./docs/images/diagram.png "Diagram")

The Secure services provided by Trusted Firmware-M can be seen on the
right-hand side of the image. These include Crypto, Attestation and Secure
Storage. It also provides secure boot via a bootloader (MCUboot). The Secure
Partition Manager (SPM) in Trusted Firmware-M provides the runtime for Secure
services.

On the left-hand side, the Non-secure software
stack is shown. This includes the FreeRTOS kernel with a CMSIS-RTOSv2
compatibility layer. These two layers are packaged together as one component
called CMSIS-FreeRTOS. The Blinky example, which uses CMSIS-RTOSv2 APIs, can be
seen above these two layers. FreeRTOS tasks can utilise Trusted Firmware-M
secure services via the PSA functional APIs.

## Supported Targets

Arm Corstone-3xx targets include an example subsystem based on the Cortex-M
CPU and Ethos NPU, alongside a range of other components in a scalable and
flexible reference package. This enables designers to build secure,
AI-capable SoCs faster.

Arm's [Fixed Virtual Platform](https://www.arm.com/products/development-tools/simulation/fixed-virtual-platforms)
is used to run the application artefacts.
The [currently released version <11.24.22>](https://developer.arm.com/downloads/-/arm-ecosystem-fvps)
of FVP is supported by the CMSIS-RTOS2 FRI project.

* [Corstone-315](https://developer.arm.com/Processors/Corstone-315)
  * Arm Cortex-M85 CPU, Ethos-U65 NPU and Mali-C55 ISP
* [Corstone-310](https://developer.arm.com/Processors/Corstone-310)
  * Arm Cortex-M85 CPU and Ethos-U55 NPU
* [Corstone-300](https://developer.arm.com/Processors/Corstone-300)
  * Arm Cortex-M55 CPU and Ethos-U55 NPU

## Supported Toolchains

* Arm GNU Toolchain (arm-none-eabi-gcc)
* Arm Compiler for Embedded (armclang)

> Note:
  The build script `./tools/scripts/build.sh` assumes
  `Arm GNU Toolchain (arm-none-eabi-gcc)` by default, append the extra option
  `--toolchain ARMCLANG` to build using Arm Compiler for Embedded Toolchain.

## Project organisation

The [document](docs/project_organisation.md) describes the organistation of the project in detail.

## Examples

This reference integration contains the following example:

* [Blinky example](docs/applications/blinky.md)
    * Demonstrates CMSIS-FreeRTOS and TF-M integration

## Software Components

### Fetching

Generally all the components used within the CMSIS-RTOS2 FRI project are fetched using `git submodules` from their official repositories into `components/` directory. Exact location and the version are recorded in the [manifest.yml](manifest.yml).

### Trusted Firmware-M

Trusted Firmware-M (TF-M) implements the Secure Processing Environment (SPE)
for Armv8-M, Armv8.1-M architectures (e.g. the Cortex-M33, Cortex-M23,
Cortex-M55, Cortex-M85 processors) and dual-core platforms. It is the platform
security architecture reference implementation aligning with PSA Certified
guidelines, enabling chips, Real Time Operating Systems and devices to become
PSA Certified. Follow the [link](https://tf-m-user-guide.trustedfirmware.org/introduction/readme.html)
for more information on Trusted Firmware-M. To have a better overview of how Trusted Firmware-M is integrated with the CMSIS-RTOS2 FRI project, you're kindly asked to check [Trusted Firmware-M component document](docs/components/trusted_firmware-m/trusted_firmware-m.md)

## License

Source code located in the *applications* directory is
available under the terms of the MIT License. See the [LICENSE](./LICENSE) file
for more details.

Other files in the repository are available under the terms specified in each
source file.