64 lines
3.0 KiB
ReStructuredText
64 lines
3.0 KiB
ReStructuredText
.. _osal:
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Operating System Abstraction Layer (OSAL)
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============================================
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Some specific information on the provided OSALs are provided.
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Linux
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-------
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This OSAL can be used to compile for Linux host systems like Ubuntu 20.04 or for
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embedded Linux targets like the Raspberry Pi. This OSAL generally requires threading support
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and real-time functionalities. For most UNIX systems, this is done by adding ``-lrt`` and
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``-lpthread`` to the linked libraries in the compilation process. The CMake build support provided
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will do this automatically for the ``fsfw`` target. It should be noted that most UNIX systems need
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to be configured specifically to allow the real-time functionalities required by the FSFW.
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Hosted OSAL
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-------------------
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This is the newest OSAL. Support for Semaphores has not been implemented yet and will propably be
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implemented as soon as C++20 with Semaphore support has matured. This OSAL can be used to run the
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FSFW on any host system, but currently has only been tested on Windows 10 and Ubuntu 20.04. Unlike
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the other OSALs, it uses dynamic memory allocation (e.g. for the message queue implementation).
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Cross-platform serial port (USB) support might be added soon.
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FreeRTOS OSAL
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------------------
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FreeRTOS is not included and the developer needs to take care of compiling the FreeRTOS sources and
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adding the ``FreeRTOSConfig.h`` file location to the include path. This OSAL has only been tested
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extensively with the pre-emptive scheduler configuration so far but it should in principle also be
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possible to use a cooperative scheduler. It is recommended to use the `heap_4` allocation scheme.
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When using newlib (nano), it is also recommended to add ``#define configUSE_NEWLIB_REENTRANT`` to
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the FreeRTOS configuration file to ensure thread-safety.
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When using this OSAL, developers also need to provide an implementation for the
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``vRequestContextSwitchFromISR`` function. This has been done because the call to request a context
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switch from an ISR is generally located in the ``portmacro.h`` header and is different depending on
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the target architecture or device.
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RTEMS OSAL
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---------------
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The RTEMS OSAL was the first implemented OSAL which is also used on the active satellite Flying Laptop.
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TCP/IP socket abstraction
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------------------------------
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The Linux and Host OSAL provide abstraction layers for the socket API. Currently, only UDP sockets
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have been imlemented. This is very useful to test TMTC handling either on the host computer
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directly (targeting localhost with a TMTC application) or on embedded Linux devices, sending
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TMTC packets via Ethernet.
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Example Applications
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----------------------
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There are example applications available for each OSAL
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- `Hosted OSAL <https://egit.irs.uni-stuttgart.de/fsfw/fsfw-example-hosted>`_
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- `Linux OSAL for MCUs <https://egit.irs.uni-stuttgart.de/fsfw/fsfw-example-linux-mcu>`_
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- `FreeRTOS OSAL on the STM32H743ZIT <https://egit.irs.uni-stuttgart.de/fsfw/fsfw-example-stm32h7-freertos>`_
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- `RTEMS OSAL on the STM32H743ZIT <https://egit.irs.uni-stuttgart.de/fsfw/fsfw-example-stm32h7-rtems>`_
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