Host Library

This Components provides the core funcionality 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 CommandLine.

Startup

Initialises SPI Flash, Uart server (in Host Drivers) and LWIP networking, then enters the main task loop. This loop services LWIP plus the task and timer queues (implemented in 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, subsquent 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 priviledged 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. 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 pre-empt it.

The set_interrupt_level function is used to ensure that threads running at different interrupt levels do not pre-empty each other, as this would introduce problems that do not exist on real hardware. The main thread is also suspended during interrupt execution.

LWIP_SERVICE_INTERVAL

Default: 2ms

LWIP stack is serviced via polling, this determines the interval.

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 Basic Utility for a worked example.

API

class CommandLine

Provides access to the command line

Anything which doesn’t start with - is interpreted as an application parameter. For example:

app param1=value

Parameters which start with - are handled by the Host Emulator. Anything after -- is passed directly to the application: 

    app -- --debug --verbose

Public Functions

const Parameters &getParameters()

Fetch a reference to the list of command-line parameters.

struct Parameter

Manages a single parameter, may be optionally separated into name=value.

Public Functions

String getName() const

Get parameter name, if there is one.

String getValue() const

Get parameter value.

Public Members

const char *text = {nullptr}

The text exactly as presented on the command line.

class Parameters : public Vector<Parameter>

List of command-line parameters, in order.

Public Functions

Parameter find(const String &name) const

Fetch parameter by name.

Parameters

  • name: Search is case-sensitive

Parameter findIgnoreCase(const String &name) const

Fetch parameter by name.

Parameters

  • name: Search is NOT case-sensitive

References

Used by

Environment Variables