Arduino LMIC 6.0.1
Arduino LoRaWAN(r) MAC in C
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Arduino-LMIC library ("MCCI LoRaWAN LMIC Library")

GitHub release GitHub commits Arduino CI

API Documentation

Contents:

  • Introduction
  • Installing
  • Getting Help
  • Features
  • Documentation
  • Known bugs and issues
  • Configuration
  • Supported hardware
  • Pre-Integrated Boards
  • PlatformIO
  • Example Sketches
  • Timing
  • Downlink data rate
  • Encoding Utilities
  • Release History
  • Contributions
  • Trademark Acknowledgements
  • License

Introduction

The "Arduino LMIC" repository contains the IBM LMIC (LoRaWAN-MAC-in-C) library, slightly modified to run in the Arduino environment, allowing using the SX1272, SX1276, SX126x transceivers and compatible modules (such as some HopeRF RFM9x modules and the Murata ABZ and 1SJ LoRa modules).

Information about the LoRaWAN protocol is summarized in LoRaWAN-at-a-glance. Full information is available from the LoRa Alliance.

For support, please open an entry in the GitHub Discussions tab of the LMIC page on github.

The base Arduino library mostly exposes the functions defined by LMIC. It makes no attempt to wrap them in a higher level API that is more in the Arduino style. To find out how to use the library itself, see the examples, or see the PDF files in the doc subdirectory.

A separate library, MCCI arduino-lorawan, provides a higher level, more Arduino-like wrapper which may be useful.

The examples in this library (apart from the compliance sketch) are somewhat primitive. A very complete cross-platform Arduino application based on the LMIC has been published by Leonel Lopes Parente (@lnlp) as LMIC-node. That application specifically targets The Things Network.

Although the wrappers in this library are designed to make the LMIC useful in the Arduino environment, the maintainers have tried to be careful to keep the core LMIC code generally useful. For example, I use this library without modification (but with wrappers) on a RISC-V platform in a non-Arduino environment.

Note on names: the library was originally ported to Arduino by Matthijs Kooijman and Thomas Telkamp, and was named Arduino LMIC. Subsequently, MCCI did a lot of work to support other regions, and ultimately took over maintenance. The Arduino IDE doesn't like two libraries with the same name, so we had to come up with a new name. In the IDE, this library appears as "MCCI LoRaWAN LMIC Library"; but we all know it by its primary header file, which is <arduino_lmic.h>.

Installing

To install this library:

  • install it using the Arduino Library manager ("Sketch" -> "Include Library" -> "Manage Libraries..."), or
  • download a zip file from GitHub using the "Download ZIP" button and install it using the IDE ("Sketch" -> "Include Library" -> "Add .ZIP Library..."
  • clone this git repository into your sketchbook/libraries folder.

For more info, see https://www.arduino.cc/en/Guide/Libraries.

Getting Help

If it's not working

Ask questions in the GitHub Discussions tab of the LMIC page on github. Wireless is tricky, so don't be afraid to ask. The LMIC has been used successfully in a lot of applications, but it's common to have problems getting it working. To keep the code size down, there are not a lot of debugging features, and the features are not always easy to use.

If you've found a bug

Raise a GitHub issue at github.com/mcci-catena/arduino-lmic.

Features

The LMIC library provides a fairly complete LoRaWAN Class A, Class B, and Class C implementation, supporting the EU-868, US-915, AU-921, AS-923, and IN-866 bands. Only a limited number of features was tested using this port on Arduino hardware, so be careful when using any of the untested features.

The library has only been tested with LoRaWAN 1.0.2/1.03 networks and does not have the separated key structure defined by LoRaWAN 1.1.

What certainly works:

  • Sending packets uplink, taking into account duty cycling.
  • Encryption and message integrity checking.
  • Custom frequencies and data rate settings.
  • Over-the-air activation (OTAA / joining).
  • Receiving downlink packets in the RX1 and RX2 windows.
  • MAC command processing.
  • Class C continuous reception (must be explicitly enabled at compile time and runtime).

What has not been tested:

  • Class B operation.
  • FSK has not been extensively tested. (Testing with the RedwoodComm RWC5020A analyzer in 2019 indicated that FSK downlink is stable but not reliable. This prevents successful completion of LoRaWAN pre-certification in regions that require support for FSK.)

If you try one of these untested features and it works, be sure to let us know (creating a GitHub issue is probably the best way for that).

Documentation

Browsable documentation (generated by Doxygen) is available at the GitHub Pages site.

The doc/ directory contains the full documentation set. Key references:

See doc/README.md for the complete documentation index.

Known bugs and issues

See the list of bugs at mcci-catena/arduino-lmic.

The LoRaWAN technology for class A devices requires devices to meet hard real-time deadlines. The Arduino environment doesn't provide built-in support for this, and this port of the LMIC doesn't really ensure it, either. It is your responsibility, when constructing your application, to ensure that you call os_runloop_once() "often enough". The API os_queryTimeCriticalJobs(ms2osticks(n)) can be used to check whether there are any deadlines due within the next n milliseconds. See Timing for details.

The Board Support Package V2.5.0 for the MCCI Murata-based boards (MCCI Catena 4610, MCCI Catena 4612, etc.) has a defect in clock calibration that prevents the compliance script from being used without modification. Versions V2.6.0 and later solve this issue.

Configuration

Configuration is done by adding settings to project_config/lmic_project_config.h. The two settings every project must define are the region and the radio transceiver.

Selecting the region

Define exactly one of the following in your project config:

-D variable Frequency
-D CFG_eu868 EU 863-870 MHz ISM
-D CFG_us915 US 902-928 MHz ISM
-D CFG_au915 Australia 915-928 MHz ISM
-D CFG_as923 Asia 923 MHz ISM
-D CFG_as923jp Asia 923 MHz ISM with Japan LBT
-D CFG_kr920 Korea 920-923 MHz ISM
-D CFG_in866 India 865-867 MHz ISM

As released, project_config/lmic_project_config.h defines CFG_us915.

Selecting the radio transceiver

Define exactly one of:

  • #define CFG_sx1272_radio 1
  • #define CFG_sx1276_radio 1
  • #define CFG_sx1261_radio 1
  • #define CFG_sx1262_radio 1

If you don't define one, the library assumes SX1276.

For the full configuration reference (LoRaWAN version, interrupts, Class C, debug output, AES library, and all other compile-time options), see Configuration Reference.

Supported hardware

This library is intended to be used with plain LoRa transceivers, connected to the Arduino CPU using a SPI bus. In particular:

  • The SX1272, SX1276 families are supported (which should include SX1273, SX1277, SX1278 and SX1279 which only differ in the available frequencies, bandwidths and spreading factors). It has been tested with both SX1272 and SX1276 chips on a variety of platforms.
  • The SX1261 and SX1262 families are supported. This has been tested with Heltec and TTGo boards.

This library contains a full LoRaWAN stack and is intended to drive these Transceivers directly. It is not intended to be used with full-stack devices like the Microchip RN2483 and the Embit LR1272E. These contain a transceiver and microcontroller that implements the LoRaWAN stack and exposes a high-level serial interface instead of the low-level SPI transceiver interface.

This library is intended to be used inside the Arduino environment. It should be architecture-independent. Users have tested this on AVR, ARM, Xtensa-based, ESP32, and RISC-V based systems.

This library can be quite heavy on 8-bit systems, especially if the fairly small ATmega 328p (such as in the Arduino Uno) is used. In the default configuration, the available 32K flash space is nearly filled up (this includes some debug output overhead, though). By disabling some features in project_config/lmic_project_config.h (like beacon tracking and ping slots, which are not needed for Class A devices), some space can be freed up.

Pre-Integrated Boards

There are two ways of using this library, either with pre-integrated boards or with manually configured boards.

The following boards are pre-integrated.

To help you know if you have to worry, we'll call such boards "pre-integrated" and prefix each section with suitable guidance.

If your board is not pre-integrated, refer to HOWTO-Manually-Configure.md.

PlatformIO

For use with PlatformIO, the lmic_project_config.h has to be disabled with the flag ARDUINO_LMIC_PROJECT_CONFIG_H_SUPPRESS. The settings are defined in PlatformIO by build_flags.

lib_deps =
MCCI LoRaWAN LMIC library
build_flags =
-D ARDUINO_LMIC_PROJECT_CONFIG_H_SUPPRESS
-D CFG_eu868=1
-D CFG_sx1276_radio=1

Example Sketches

This library provides several examples.

Timing

The library must track precise timing for opening RX1 and RX2 receive windows after uplink transmissions. Key points:

  • Call os_runloop_once() frequently, especially during transmit/receive cycles. Use os_queryTimeCriticalJobs(ms2osticks(n)) to check if the LMIC needs attention within n milliseconds.
  • By default, the library polls DIO pins. Optionally, define LMIC_USE_INTERRUPTS for hardware interrupt-driven timing (requires DIO pins wired to interrupt-capable Arduino pins).
  • For boards with inaccurate oscillators (100-4000 ppm), call LMIC_setClockError() to widen the receive window. See Timing for the full discussion including LMIC_setClockError() API reference and interrupt implementation details.

Downlink data rate

Note that the data rate used for downlink packets in the RX2 window varies by region. Consult your network's manual for any divergences from the LoRaWAN Regional Parameters. This library assumes that the network follows the regional default.

Some networks use different values than the specification. For example, in Europe, the specification default is DR0 (SF12, 125 kHz bandwidth). However, iot.semtech.com and The Things Network both used SF9 / 125 kHz or DR3). If using over-the-air activation (OTAA), the network will download RX2 parameters as part of the JoinAccept message; the LMIC will honor the downloaded parameters.

However, when using personalized activate (ABP), it is your responsibility to set the right settings, e.g. by adding this to your sketch (after calling LMIC_setSession). ttn-abp.ino already does this.

LMIC.dn2Dr = DR_SF9;

Encoding Utilities

See Encoding Utilities for sflt16, uflt16, sflt12, uflt12 format descriptions and JavaScript decoder functions.

Release History

Current version: 6.0.0 – adds Class C support, secure element abstraction, SX1261/SX1262 radio drivers. Breaking change: LMIC.rxtime renamed to LMIC.nextRxTime.

See CHANGELOG.md for the full release history.

Contributions

This library started from the IBM V1.5 open-source code.

  • Thomas Telkamp and Matthijs Kooijman ported V1.5 to Arduino and did a lot of bug fixing.
  • Terry Moore, LeRoy Leslie, Frank Rose, and ChaeHee Won did a lot of work on US support.
  • Terry Moore added the AU915, AS923, KR920 and IN866 regions, and created the regionalization framework, and did corrections for LoRaWAN 1.0.3 compliance testing.
  • @tanupoo of the WIDE Project debugged AS923JP and LBT support.
  • @frazar contributed numerous features, e.g. network time support, CI testing, documentation improvements.
  • @manuelbl contributed numerous ESP32-related patches and improvements.
  • @ngraziano did extensive testing and contributed numerous ADR-related patches.
  • Tristan Webber (@TristanWebber) contributed sx1261 and sx1262 support.

There are many others, who have contributed code and also participated in discussions, performed testing, reported problems and results. Thanks to all who have participated. We hope to use something like All Contributors to help keep this up to date, but so far the automation isn't working.

Trademark Acknowledgements

LoRa is a registered trademark of Semtech Corporation. LoRaWAN is a registered trademark of the LoRa Alliance.

MCCI and MCCI Catena are registered trademarks of MCCI Corporation.

All other trademarks are the properties of their respective owners.

License

The upstream files from IBM v1.6 are based on the Berkeley license, and the merge which synchronized this repository therefore migrated the core files to the Berkeley license. However, modifications made in the Arduino branch were done under the Eclipse license, so the overall license of this repository is still Eclipse Public License v1.0. The examples which use a more liberal license. Some of the AES code is available under the LGPL. Refer to each individual source file for more details, but bear in mind that until the upstream developers look into this issue, it is safest to assume the Eclipse license applies.

Support Open Source Hardware and Software

MCCI invests time and resources providing this open source code, please support MCCI and open-source hardware by purchasing products from MCCI, Adafruit and other open-source hardware/software vendors!