LoRa is a low-power long-range wireless technology, developed by a French startup, later on bought by Semtech, a supplier of analog and mixed-signal semiconductor products.
Libelium is a Spanish company delivering an open source sensor platform for the Internet of Things.
Libelium added LoRa support to its offering some months ago. To start playing with LoRa, you simply have to use what Libelium names a Plug & Sense (mainly a waterproof case integrating a microcontroller board, several sensors and a wireless module, a LoRa one in our case) and their LoRa gateway, a USB stick that you can plug into a PC.
LoRa uses spread spectrum technology, on different channels. This means that the Plug & Sense and the gateway can be configured in several different ways, depending on parameters such as channel, bandwidth, coding rate and spreading factor. On Plug & Sense side, the developer can use the available software library. On gateway side, the developer has to send configuration messages to the USB stick using a terminal emulator. This is not very convenient.
Libelium LoRa Gateway Controller
This application implements a simple controller for the Libelium LoRa gateway: it allows to configure various gateway parameters, and to read those parameters. Additionally, it displays messages sent to the gateway by the Plug & Sense.
The application user interface (UI) provides following elements:
- a serial port device selector
- a button to send READ frames
- a button to send SET frames
- several elements to define gateway parameters, used by the SET frame
- a first scrolling list
- a second scrolling list
- the top combo box allows to select the serial port to be used. Other buttons are active only once the serial port is selected. Once selected, it's no more possible to change the serial port.
- the Send READ command button sends the READ frame to the gateway. The gateway answers with its current configuration.
- the Send SET command sends the SET command to the gateway, with parameters set to the values selected on the right-hand side of the window: frequency and channel, address, bandwidth, coding rate and spreading factor.
- below those buttons, there are two scrolling lists of messages. The top one displays all frames received from the gateway. Those frames can be either answers to commands sent to the gateway, or data received from the Plug & Sense. Every message is timestamped.
- the bottom list displays messages generated by the applications. These messages inform the user
about ongoing operations. In current version, following messages are displayed:
- at startup time: the list of available serial ports
- indication of the use of the command buttons
- frame sent by the use of a command button
Developing this type of application quite often leads to discovering some discrepancies between documentation and reality. In our case, we can list:
- frames received from the Plug & Sense are terminated by an undocumented sequence of two characters (Carriage Return and Line Feed)
- the gateway does not check the CRC of the command message it receives
- if a data frame sent by the Plug & Sense is received by the gateway almost at the same time a command is sent to it, format of data received by the PC is incorrect
The Plug & Sense can send two types of frames: ASCII frames and binary frames. In current version, only ASCII frames are supported.
Installation of source code
The Libelium LoRa Gateway Controller uses the RXTX library to access the serial port. You have to install it in order to be able to run the application. For installation procedure, please refer to this page, or see below.
Additionally, the application relies on JavaFX. See below.
This repository provides source code files for Eclipse. Of course, those files can be used in any other development environment. But following explanations relate to Eclipse only. Additionally, information is provided for a PC running Linux Mint, a Linux distribution derived from Ubuntu.
Installation of RXTX
- install package
Installation of JavaFX
- configure Eclipse for JavaFX, as explained here
- download Scene Builder from here. Then, in Eclipse, set the path to Scene Builder executable (Window / Preferences / JavaFX). This step is optional.
- in Eclipse, switch to the Git perspective and clone this Git repository.
Configuration of Eclipse for RXTX
You should not have to go through the two steps below, if you imported the project from the repository as directed above. But it can be useful to know what has to be done for RXTX, in a more general case:
/usr/share/java/RXTXcomm-2.2pre2.jarexternal JAR to the Eclipse project
- right-click on the jar in the list of referenced libraries in the Eclipse project,
select Properties / Native Library and enter the directory containing native libraries:
- create a Run configuration. For project, use
LoraGatewayController. For main class, use
- create a runnable jar, using File/Export.../Java/Runnable JAR file
How to run the application
- run the JAR file created above (or the one in this repository):
java -jar <JARFile>