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Temperature control sensor reading and REST Server

This module hold Kotlin implementation of Temperature Reading from Arduino via a serial port and REST server exposing temperature reading and control to any UIs.

    Please note that this code is not designed to work on the public networks like Internet, as it is missing crucial security!

A list of technologies involved:

  • JVM 8, and it has to be at least 8 as Vert.x 3.x doesn't work with anything before version 8
  • RXTX Java - a Java library for communicating with serial ports (included in the libs folder)
  • Vert.x 3.2.1 framework - framework for event driven applications, highly scalable and super fast. Love it!
  • Kotlin programming language - because I wanted to learn another language for JVM :) It turned to be pretty good.
  • H2 Database - for file based simple storage of the historical temperature data
  • Gradle for building the lot

Architecture and flow

Main entry point to the application is via TemperatureApp class. It starts all verticles that are responsible for specific event handling:

  • SerialPortTemperatureVerticle - registers itself as a listener on specified serial port (Arduino USB connection). It receives temperature updates from Arduino and sends control message with temperature to set to it.

Building the binaries

Project uses Gradle to build fat jar file. To build the project run:

    ./gradlew clean shadowJar

Build jar will be located in build/libs/ folder.

There is also a task that packs binaries, scripts and config files into a single zip.

    ./gradlew clean prepareDist

Prepared zip file will be located in build/dist/ folder.

Running the app

SerialPort verticle is using RXTX Java Library which requires JNI library. On Mac, I'm using the one in [libs][./libs] folder.

On Raspberry Pi I installed the JNI with command:

    sudo apt-get -y install rxtx-jni

You should be able to run the start_service.sh script that starts the service.

Alternatively you can run the following from the command line:

    java -Djava.library.path=$JNI_LOCATION -jar $JAR_FILE  -conf $CONFIG_FILE

You can try to stop the service with stop_service.sh script :)

Local dev with serial port

I used socat command to simulate Arduino on my Mac for development and testing. You can lunch something line:

   → sudo socat -d -d -d pty,raw,echo=0,mode=666,link=/tmp/foo -

and use /tmp/foo as the serial port device path.