esp-open-rtos

A community developed open source FreeRTOS-based framework for ESP8266 WiFi-enabled microcontrollers. Intended for use in both commercial and open source projects.

Originally based on, but substantially different from, the Espressif IOT RTOS SDK.

Quick Start

• Install esp-open-sdk, build it with make STANDALONE=n, then edit your PATH and add the generated toolchain bin directory. (Despite the similar name esp-open-sdk has different maintainers - but we think it's fantastic!)

  (Other toolchains may also work, as long as a gcc cross-compiler is available on the PATH and libhal (and libhal headers) are compiled and available to gcc. The proprietary Tensilica "xcc" compiler will probably not work.)

• Install esptool.py and make it available on your PATH. If you used esp-open-sdk then this is done already.

• The esp-open-rtos build process uses GNU Make, and the utilities sed and grep. If you built esp-open-sdk then you probably have these already.

• Use git to clone the esp-open-rtos project (note the --recursive):

git clone --recursive https://github.com/Superhouse/esp-open-rtos.git
cd esp-open-rtos

• To build any examples that use WiFi, edit include/ssid_config.h and change the two macro defines:

#define WIFI_SSID "mywifissid"
#define WIFI_PASS "my secret password"

Remove the #warning and follow the git ignore instructions to keep your credentials from being pushed to Github.

• Build an example project (found in the 'examples' directory) and flash it to a serial port:

make flash -j4 -C examples/http_get ESPPORT=/dev/ttyUSB0

Run make help -C examples/http_get for a summary of other Make targets.

The Build Process wiki page has in-depth details of the build process.

Goals

• Provide professional-quality framework for WiFi-enabled RTOS projects on ESP8266.
• Open source code for all layers above the MAC layer, ideally lower layers if possible (this is a work in progress, see Issues list.
• Leave upstream source clean, for easy interaction with upstream projects.
• Flexible build and compilation settings.

Current status is alpha quality, under development. AP STATION mode (ie wifi client mode) and UDP/TCP client modes are tested. Other functionality should work. Contributors and testers are welcome!

Open Source Components

• FreeRTOS V7.5.2
• lwIP v1.4.1, modified via the esp-lwip project by @kadamski.
• axTLS compiled from development version v1.5.3, plus modifications for low memory devices.
• newlib v2.2.0, with patches for xtensa support and locking stubs for thread-safe operation on FreeRTOS.

For details of how third party libraries are integrated, see the wiki page.

Binary Components

Binary libraries (inside the lib dir) are all supplied by Espressif as part of their RTOS SDK. These parts were MIT Licensed.

As part of the esp-open-rtos build process, all binary SDK symbols are prefixed with sdk_. This makes it easier to differentiate binary & open source code, and also prevents namespace conflicts.

Some binary libraries appear to contain unattributed open source code:

• libnet80211.a & libwpa.a appear to be based on FreeBSD net80211/wpa, or forks of them. (See this issue).
• libudhcp has been removed from esp-open-rtos. It was released with the Espressif RTOS SDK but udhcp is GPL licensed.

Code Structure

• examples contains a range of example projects (one per subdirectory). Check them out!
• include contains header files from Espressif RTOS SDK, relating to the binary libraries & Xtensa core.
• core contains source & headers for low-level ESP8266 functions & peripherals. core/include/esp contains useful headers for peripheral access, etc. Still being fleshed out. Minimal to no FreeRTOS dependencies.
• FreeRTOS contains FreeRTOS implementation, subdirectory structure is the standard FreeRTOS structure. FreeRTOS/source/portable/esp8266/ contains the ESP8266 port.
• lwip and axtls contain the lwIP TCP/IP library and the axTLS TLS library ('libssl' in the esp8266 SDKs), respectively. See Third Party Libraries wiki page for details.

Licensing

• BSD license (as described in LICENSE) applies to original source files, lwIP, and axTLS. lwIP is Copyright (C) Swedish Institute of Computer Science. axTLS is Copyright (C) Cameron Rich.

• FreeRTOS is provided under the GPL with the FreeRTOS linking exception, allowing non-GPL firmwares to be produced using FreeRTOS as the RTOS core. License details in files under FreeRTOS dir. FreeRTOS is Copyright (C) Real Time Engineers Ltd.

• Source & binary components from the Espressif IOT RTOS SDK were released under the MIT license. Source code components are relicensed here under the BSD license. The original parts are Copyright (C) Espressif Systems.

• Newlib is covered by several copyrights and licenses, as per the files in the libc directory.

Contributions

Contributions are very welcome!

• If you find a bug, please raise an issue to report it.

• If you have feature additions or bug fixes then please send a pull request.

• There is a list of outstanding 'enhancements' in the issues list. Contributions to these, as well as other improvements, are very welcome.

If you are contributing code, please ensure that it can be licensed under the BSD open source license. Specifically:

• Code from Espressif IoT SDK cannot be merged, as it is provided under either the "Espressif General Public License" or the "Espressif MIT License", which are not compatible with the BSD license.

• Recent releases of the Espressif IoT RTOS SDK cannot be merged, as they changed from MIT License to the "Espressif MIT License" which is not BSD compatible. The Espressif binaries used in esp-open-rtos were taken from revision ec75c85, as this was the last MIT Licensed revision.

For code submissions based on reverse engineered binary functionality, please either reverse engineer functionality from MIT Licensed Espressif releases or make sure that the reverse engineered code does not directly copy the code structure of the binaries - it cannot be a "derivative work" of an incompatible binary.

The best way to write suitable code is to first add documentation somewhere like the esp8266 reverse engineering wiki describing factual information gained from reverse engineering - such as register addresses, bit masks, orders of register writes, etc. Then write new functions referring to that documentation as reference material.

Coding Style

For new contributions, please use BSD style and indent using 4 spaces. If you're an emacs user then there is a .dir-locals.el file in the root which configures cc-mode.

Upstream code is left with the indentation and style of the upstream project.

Sponsors

Work on parts of esp-open-rtos has been sponsored by SuperHouse Automation.