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Running Applications on Host

Note

Running IDF applications on host is currently still an experimental feature, thus there is no guarantee for API stability. However, user feedback via the ESP-IDF GitHub repository or the ESP32 forum is highly welcome, and may help influence the future of design of the IDF host-based applications.

This document provides an overview of the methods to run IDF applications on Linux, and what type of IDF applications can typically be run on Linux.

Introduction

Typically, an IDF application is built (cross-compiled) on a host machine, uploaded (i.e., flashed) to an ESP chip for execution, and monitored by the host machine via a UART/USB port. However, execution of an IDF application on an ESP chip (hence forth referred to as "running on target") can be limiting in various development/usage/testing scenarios.

Therefore, it is possible for an IDF application to be built and executed entirely within the same Linux host machine (hence forth referred to as "running on host"). Running ESP-IDF applications on host has several advantages:

  • No need to upload to a target.
  • Faster execution on a host machine, compared to running on an ESP chip.
  • No requirements for any specific hardware, except the host machine itself.
  • Easier automation and setup for software testing.
  • Large number of tools for code and runtime analysis (e.g. Valgrind).

A large number of IDF components depend on chip-specific hardware. These hardware dependencies must be mocked or simulated when running on host. ESP-IDF currently supports the following mocking and simulation approaches:

  1. Using the FreeRTOS POSIX/Linux simulator that simulates FreeRTOS scheduling. On top of this simulation, other APIs are also simulated or implemented when running on host.
  2. Using CMock to mock all dependencies and run the code in complete isolation.

In principle, it is possible to mix both approaches (POSIX/Linux simulator and mocking using CMock), but this has not been done yet in ESP-IDF. Note that despite the name, the FreeRTOS POSIX/Linux simulator currently also works on MacOS. Running IDF applications on host machines is often used for testing. However, simulating the environment and mocking dependencies does not fully represent the target device. Thus, testing on the target device is still necessary, though with a different focus that usually puts more weight on integration and system testing.

Note

Another possibility to run applications on the host is to use the QEMU simulator. However, QEMU development for IDF applications is currently work in progress and has not been documented yet.

CMock-Based Approach

This approach uses the CMock framework to solve the problem of missing hardware and software dependencies. CMock-based applications running on the host machine have the added advantage that they usually only compile the necessary code, i.e., the (mostly mocked) dependencies instead of the entire system. For a general introduction to Mocks and how to configure and use them in ESP-IDF, please refer to :ref:`mocks`.

POSIX/Linux Simulator Approach

The FreeRTOS POSIX/Linux simulator is available on ESP-IDF as a preview target already. It is the base for the Linux target which is already available as a preview. Using this simulator, IDF components can be implemented on the host to make them available to IDF applications when running on host. Currently, only a limited number of components are ready to be built on Linux. Furthermore the functionality of each component ported to Linux may also be limited or different compared to the functionality when building that component for a chip target. For more information if the desired components are supported on Linux, please refer to :ref:`component-linux-mock-support`.

Requirements

If any mocks are used, then Ruby is required, too.

Build and Run

To build the application on Linux, the target has to be set to linux and then it can be built and run:

idf.py --preview set-target linux
idf.py build
idf.py monitor

Component Linux/Mock Support Overview

Note that any "Yes" here does not necessarily mean a full implementation or mocking. It can also mean a partial implementation or mocking of functionality. Usually, the implementation or mocking is done to a point where enough functionality is provided to build and run a test application.

Component Mock Simulation
driver Yes No
esp_common No Yes
esp_event Yes Yes
esp_hw_support Yes Yes
esp_partition Yes No
esp_rom No Yes
esp_system No Yes
esp_timer Yes No
esp_tls Yes No
freertos Yes Yes
hal No Yes
heap No Yes
http_parser Yes No
log No Yes
lwip Yes No
soc No Yes
spi_flash Yes No
tcp_transport Yes No