LoRa-ATtiny-Node

If you are looking for the generic SlimLoRa library for use with Arduinos click HERE.

This repository contains the SlimLoRa LoRaWAN library with a sample project for ATtiny85 chips. It uses AES encryption routines originally written by Ideentron B.V.. SlimLoRa is compatible with all radio chips based on the Semtech SX1276 (e.g. HopeRF RFM95).

Currently this library is heavily optimized for ATtiny85 chips and needs changes to run on other devices (e.g. Arduino). Furthermore, currently only the EU-868 band is supported.

SlimLoRa implements the ABP and OTAA activation schemes. It has support for downlink messages and the Adaptive Data Rate (ADR) mechanism.

Although the basic things of the LoRaWAN 1.0.3 Class A specification are implemented, this library does not cover the entire specification and thus is not fully LoRaWAN 1.0 compliant. Please verify its behavior before using it on public networks.
It also does not enforce a duty cycle. This must be ensured by the user.

Contents:

• Purpose
• Installing
• Features
• Requirements and Limitations
• Configuration
• Supported hardware
• Example Program
• Timing
• Release History
• Sample Board
• Trademark Acknowledgements
• License

Purpose

I developed SlimLoRa and this sample project as a fun project to prove that a full LoRaWAN implementation with support for various sensors can run on an ATtiny85 MCU with only 5 data pins, 8K of flash memory, 512 bytes of EEPROM, 512 bytes of SRAM and without an external clock.

Installing

To compile and flash this library, attach your USB-ASP programmer and execute the following commands:

git clone https://github.com/novag/LoRa-ATtiny-Node
cd LoRa-ATtiny-Node
cp config.example.h config.h # Insert your key(s)
make
make program

Features

This library provides a LoRaWAN 1.0 Class A implementation for the EU-868 band.

The library has some support for LoRaWAN 1.1 which is not usable yet.

• Sending uplink packets, not taking into account duty cycles.
• Message encryption and message integrity checking.
• Over-the-Air Activation (OTAA).
• Activation by Personalization (ABP).
• Adaptive Data Rate (ADR).
• Receiving downlink packets in the RX1 and RX2 windows.
• MAC command processing for LinkAdr, RxParamSetup, DevStatus and RxTimingSetup requests.

Requirements and Limitations

No event handling

This library does not implement any kind of event handling. A call to the Join and SendData methods will block for several seconds until the end of the second receive window.

Be sure to put connected sensors into sleep mode before sending data to save energy!

Timer0

SlimLoRa uses the Timer0 on every call of the Join or SendData methods. Between these calls Timer0 can be used by the user for other purposes. See also timing.h and timing.c.

Memory requirements

SlimLoRa uses a maximum of 141 bytes of RAM for its stack and 103 bytes for global symbols.

The current project has a maximum total RAM usage of about 250 bytes. On an ATtiny85 you should never call into the Join and SendData methods from deeply nested functions. Analyze and profile your program!

Configuration

LoRaWAN settings and attached sensors can be configured in the config.h header file.

Debug output

Disable all sensors and attach a UART console to pin 4.

make DEBUG=1
make program

Supported hardware

ATtiny85 with radios based on the SX1276 are supported (e.g. HopeRF RFM95).

Example Program

This repository contains a working sample project that sends temperature, humidity and voltage data every 15 minutes to the network. The user can choose between ABP and OTAA activation and can enable or disable ADR.

The ATtiny can act as an SPI, I2C and Dallas 1-Wire master. Thus the following three sensors are currently supported:

• DHT22 (Non-standardized OneWire)
• DS18B20 (Dallas 1-Wire)
• SI7021 (I2C slave)

That means, with the available ports, in addition to the radio module, either one non-standardized OneWire device, multiple Dallas 1-Wire devices, multiple I2C devices or one additonal SPI slave device can be connected.

Only select a single device in the configuration file. Otherwhise the first selected device will take precedence.

Timing

Release History

• V0.1.0 Initial release.

Sample Board

Contributions

This library started from parts written by Ideetron B.V.. Of these, almost only the AES routines are left. Thanks to Ideetron B.V.!

• Hendrik Hagendorn

• Ideentron B.V. - RFM95W_Nexus

Trademark Acknowledgements

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

All other trademarks are the properties of their respective owners.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.