.. _module-pw_system: ========= pw_system ========= .. pigweed-module:: :name: pw_system .. warning:: This module is an early work-in-progress towards an opinionated framework for new projects built on Pigweed. It is under active development, so stay tuned! pw_system is quite different from typical Pigweed modules. Rather than providing a single slice of vertical functionality, pw_system pulls together many modules across Pigweed to construct a working system with RPC, Logging, an OS Abstraction layer, and more. pw_system exists to greatly simplify the process of starting a new project using Pigweed by drastically reducing the required configuration space required to go from first signs of on-device life to a more sophisticated production-ready system. -------------------- Trying out pw_system -------------------- If you'd like to give pw_system a spin and have a STM32F429I Discovery board, refer to the board's :ref:`target documentation` for instructions on how to build the demo and try things out If you don't have a discovery board, there's a simulated device variation that you can run on your local machine with no additional hardware. Check out the steps for trying this out :ref:`here`. -------------- Target Bringup -------------- Bringing up a new device is as easy as 1-2-3! (Kidding, this is a work in progress) #. **Configure the build.** How exactly to do this depends on the build system. * **GN**: Create a ``pw_system_target`` in your GN build. This is what will control the configuration of your target from a build system level. This includes which compiler will be used, what architecture flags will be used, which backends will be used, and more. A large quantity of configuration will be pre-set to work with pw_system after you select the CPU and scheduler your target will use, but your target will likely need to set a few other things to get to a fully working state. * **Bazel**: Add a dependency on ``@pigweed//pw_system`` to your ``cc_binary``, and set one `label flag `__, ``@pigweed//pw_system:extra_platform_libs``. Point it to a ``cc_library`` containing any platform-dependent dependencies of your ``pw_system`` instantiation. In particular, this should include platform-specific initialization code (see next point) and the custom :ref:`pw_linker_script ` (if any) to use when linking the ``pw_system`` binary. .. warning:: You should always add the ``alwayslink = 1`` attribute to the target you point ``@pigweed//pw_system:extra_platform_libs`` to. This is because Bazel `links files in topological order `__, but the dependencies from ``extra_platform_libs`` may appear before the objects they are used in. The ``alwayslink = 1`` will prevent the linker from erroneously garbage-collecting them. #. **Write target-specific initialization.** Most embedded devices require a linker script, manual initialization of memory, and some clock initialization. pw_system leaves this to users to implement as the exact initialization sequence can be very project-specific. All that's required is that after early memory initialization and clock configuration is complete, your target initialization should call ``pw::system::Init()`` and then start the RTOS scheduler (e.g. ``vTaskStartScheduler()``). #. **Implement ``pw::system::UserAppInit()`` in your application.** This is where most of your project's application-specific logic goes. This could be starting threads, registering RPC services, turning on Bluetooth, or more. In ``UserAppInit()``, the RTOS will be running so you're free to use OS primitives and use features that rely on threading (e.g. RPC, logging). Pigweed's ``stm32f429i_disc1_stm32cube`` target demonstrates what's required by the first two steps. The third step is where you get to decide how to turn your new platform into a project that does something cool! It might be as simple as a blinking LED, or something more complex like a Bluetooth device that brews you a cup of coffee whenever ``pw watch`` kicks off a new build. .. note:: Because of the nature of the hard-coded conditions in ``pw_system_target``, you may find that some options are missing for various RTOSes and architectures. The design of the GN integration is still a work-in-progress to improve the scalability of this, but in the meantime the Pigweed team welcomes contributions to expand the breadth of RTOSes and architectures supported as ``pw_system_target``\s. GN Target Toolchain Template ============================ This module includes a target toolchain template called ``pw_system_target`` that reduces the amount of work required to declare a target toolchain with pre-selected backends for pw_log, pw_assert, pw_malloc, pw_thread, and more. The configurability and extensibility of this template is relatively limited, as this template serves as a "one-size-fits-all" starting point rather than being foundational infrastructure. .. code-block:: # Declare a toolchain with suggested, compiler, compiler flags, and default # backends. pw_system_target("stm32f429i_disc1_stm32cube_size_optimized") { # These options drive the logic for automatic configuration by this # template. cpu = PW_SYSTEM_CPU.CORTEX_M4F scheduler = PW_SYSTEM_SCHEDULER.FREERTOS # Optionally, override pw_system's defaults to build with clang. system_toolchain = pw_toolchain_arm_clang # The pre_init source set provides things like the interrupt vector table, # pre-main init, and provision of FreeRTOS hooks. link_deps = [ "$dir_pigweed/targets/stm32f429i_disc1_stm32cube:pre_init" ] # These are hardware-specific options that set up this particular board. # These are declared in ``declare_args()`` blocks throughout Pigweed. Any # build arguments set by the user will be overridden by these settings. build_args = { pw_third_party_freertos_CONFIG = "$dir_pigweed/targets/stm32f429i_disc1_stm32cube:stm32f4xx_freertos_config" pw_third_party_freertos_PORT = "$dir_pw_third_party/freertos:arm_cm4f" pw_sys_io_BACKEND = dir_pw_sys_io_stm32cube dir_pw_third_party_stm32cube = dir_pw_third_party_stm32cube_f4 pw_third_party_stm32cube_PRODUCT = "STM32F429xx" pw_third_party_stm32cube_CONFIG = "//targets/stm32f429i_disc1_stm32cube:stm32f4xx_hal_config" pw_third_party_stm32cube_CORE_INIT = "" pw_boot_cortex_m_LINK_CONFIG_DEFINES = [ "PW_BOOT_FLASH_BEGIN=0x08000200", "PW_BOOT_FLASH_SIZE=2048K", "PW_BOOT_HEAP_SIZE=7K", "PW_BOOT_MIN_STACK_SIZE=1K", "PW_BOOT_RAM_BEGIN=0x20000000", "PW_BOOT_RAM_SIZE=192K", "PW_BOOT_VECTOR_TABLE_BEGIN=0x08000000", "PW_BOOT_VECTOR_TABLE_SIZE=512", ] } } # Example for the Emcraft SmartFusion2 system-on-module pw_system_target("emcraft_sf2_som_size_optimized") { cpu = PW_SYSTEM_CPU.CORTEX_M3 scheduler = PW_SYSTEM_SCHEDULER.FREERTOS link_deps = [ "$dir_pigweed/targets/emcraft_sf2_som:pre_init" ] build_args = { pw_log_BACKEND = dir_pw_log_basic #dir_pw_log_tokenized pw_log_tokenized_HANDLER_BACKEND = "//pw_system:log" pw_third_party_freertos_CONFIG = "$dir_pigweed/targets/emcraft_sf2_som:sf2_freertos_config" pw_third_party_freertos_PORT = "$dir_pw_third_party/freertos:arm_cm3" pw_sys_io_BACKEND = dir_pw_sys_io_emcraft_sf2 dir_pw_third_party_smartfusion_mss = dir_pw_third_party_smartfusion_mss_exported pw_third_party_stm32cube_CONFIG = "//targets/emcraft_sf2_som:sf2_mss_hal_config" pw_third_party_stm32cube_CORE_INIT = "" pw_boot_cortex_m_LINK_CONFIG_DEFINES = [ "PW_BOOT_FLASH_BEGIN=0x00000200", "PW_BOOT_FLASH_SIZE=200K", # TODO: b/235348465 - Currently "pw_tokenizer/detokenize_test" requires at # least 6K bytes in heap when using pw_malloc:bucket_block_allocator. # The heap size required for tests should be investigated. "PW_BOOT_HEAP_SIZE=7K", "PW_BOOT_MIN_STACK_SIZE=1K", "PW_BOOT_RAM_BEGIN=0x20000000", "PW_BOOT_RAM_SIZE=64K", "PW_BOOT_VECTOR_TABLE_BEGIN=0x00000000", "PW_BOOT_VECTOR_TABLE_SIZE=512", ] } } ------- Metrics ------- The log backend is tracking metrics to illustrate how to use pw_metric and retrieve them using `Device.get_and_log_metrics()`. ------- Console ------- The ``pw-system-console`` can be used to interact with the targets. See :ref:`module-pw_system-cli` for detailed CLI usage information. .. toctree:: :hidden: :maxdepth: 1 cli ------------------- Multi-endpoint mode ------------------- The default configuration serves all its traffic with the same channel ID and RPC address. There is an alternative mode that assigns a separate channel ID and address for logging. This can be useful if you want to separate logging and primary RPC to ``pw_system`` among multiple clients. To use this mode, add the following to ``gn args out``: .. code-block:: pw_system_USE_MULTI_ENDPOINT_CONFIG = true The settings for the channel ID and address can be found in the target ``//pw_system:multi_endpoint_rpc_overrides``. .. _module-pw_system-logchannel: --------------------- Extra logging channel --------------------- In multi-processor devices, logs are typically forwarded to a primary application-class core. By default, ``pw_system`` assumes a simpler device architecture where a single processor is communicating with an external host system (e.g. a Linux workstation) for developer debugging. This means that logging and RPCs are expected to coexist on the same channel. It is possible to redirect the logs to a different RPC channel output by configuring ``PW_SYSTEM_LOGGING_CHANNEL_ID`` to a different channel ID, but this would still mean that logs would inaccessible from either the application-class processor, or the host system. The logging multisink can be leveraged to address this completely by forwarding a copy of the logs to the application-class core without impacting the behavior of the debug communication channel. This allows ``pw-system-console`` work as usual, while also ensuring logs are available from the larger application-class processor. Additionally, this allows the debug channel to easily be disabled in production environments while maintaining the log forwarding path through the larger processor. An example configuration is provided below: .. code-block:: config("extra_logging_channel") { defines = [ "PW_SYSTEM_EXTRA_LOGGING_CHANNEL_ID=2" ] } pw_system_target("my_system") { global_configs = [ ":extra_logging_channel" ] } Once you have configured pw_system as shown in the example above, you will still need to define an RPC channel for the channel ID that you selected so the logs can be routed to the appropriate destination. --------------- pw_system:async --------------- ``pw_system:async`` is a new version of ``pw_system`` based on :ref:`module-pw_async2` and :ref:`module-pw_channel`. It provides an async dispatcher, which may be used to run async tasks, including with C++20 coroutines. To use ``pw_system:async``, add a dependency on ``@pigweed//pw_system:async`` in Bazel. Then, from your main function, invoke :cpp:func:`pw::SystemStart` with a :cpp:type:`pw::channel::ByteReaderWriter` to use for IO. .. literalinclude:: system_async_test.cc :language: cpp :linenos: :start-after: [pw_system-async-example-main] :end-before: [pw_system-async-example-main] pw_system:async Linux example ============================= ``//pw_system/system_async_host_simulator_example`` is an example app for running ``pw_system:async`` on a Linux host. Running the example requires two terminals. In the first terminal, start the ``pw_system:async`` instance: .. code-block:: console $ bazelisk run //pw_system/system_async_host_simulator_example That will wait for a TCP connection from the ``pw_system`` console. To connect to it from the console, run the following: .. code-block:: console $ bazelisk run //pw_system/py:pw_system_console -- -s 127.0.0.1:33000 Debugging pw_system_console with VSCode --------------------------------------- When running a python script through bazel, python is run inside a bazel sandbox, which can make re-creating this environment difficult when running the script outside of bazel to attach a debugger. To simplify debugging setup, Pigweed makes available the `debugpy `__ package to ease attaching ``pw_system_console``. First configure VSCode to add the following to the configuration section of ``launch.json``. This file can be automatically opened by selecting ``Run -> Open Configurations```, or ``Run -> Add Configuration`` if there is no existing ``launch.json``. .. TODO: b/372079357 - can this be automated by the VSCode plugin? .. code-block:: json "configurations": [ { "name": "Python Debugger: Remote Attach", "type": "debugpy", "request": "attach", "connect": { "host": "localhost", "port": 5678 }, "pathMappings": [ { "localRoot": "${workspaceFolder}", "remoteRoot": "." } ] } ] Next, run the console through bazel, adding the argument(s) ``--debugger-listen`` and optionally ``--debugger-wait-for-client`` to pause the console until the debugger attached. For example: .. code-block:: console $ bazelisk run //pw_system/py:pw_system_console -- --debugger-listen Once the console has been started, simply select ``Run -> Start Debugging`` and the VS code debugger will automatically attach to the running python console. API reference ============= .. doxygenfunction:: pw::SystemStart(channel::ByteReaderWriter&) .. doxygenfunction:: pw::System .. doxygenclass:: pw::system::AsyncCore :members: