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Host Library

This Components provides the core functionality for the Host Emulator:

Sockets

Classes to provide simple Berkeley socket support for both Linux and Windows

Options

Command line argument parsing. Applications may pass parameters and access them using the :cpp:class:`CommandLine`.

Startup

Initialises :component-host:`spi_flash`, Uart server (in :component-host:`driver`) and :component-host:`lwip` networking, then enters the main task loop. This loop services LWIP plus the task and timer queues (implemented in :component-host:`esp_hal`). The Ctrl+C keypress is trapped to provide an orderly exit. If the system has become stuck in a loop or is otherwise unresponsive, subsequent Ctrl+C presses will force a process termination.

Threads and Interrupts

The emulator uses Posix threads (pthread library) to perform background processing which would probably be done in hardware or which is outside of the framework.

Ideally we'd use SCHED_FIFO to disable time-slicing and more closely resemble how interrupts work on a single-core CPU. However, this mode isn't supported in Windows, and Linux requires privileged access and can potentially crash the system. Best avoided, I think.

All ESP code runs at a specific interrupt level, where 0 represents regular code. Interrupts are triggered from a separate thread (a CThread instance) which calls :cpp:func:` When an interrupt occurs, the level is raised according to the priority of that interrupt. Until that code has finished, only interrupts of a higher priority will preempt it.

Thread 'interrupt' code is sandwiched between calls to interrupt_begin() and interrupt_end(), which blocks interrupts from other threads at the same or lower level. The threads aren't suspended but will block if they call interrupt_begin(). However, the main thread (level 0) is halted to reflect normal interrupt behaviour.

.. envvar:: HOST_PARAMETERS

   Set this value to pass additional parameters to a Host application.
   For example::

      make run HOST_PARAMETERS='param1=12 param2="parameter with spaces"'
      make run HOST_PARAMETERS="param1=12 param2=\"parameter with spaces\""

   See :sample:`Basic_Utility` for a worked example.

API

.. doxygenclass:: CommandLine
   :members: