ArduinoProps library

1. Installation and usage
2. Escape room 2.0 prop with Arduino
3. ArduinoProps library value for escape room 2.0
4. Application protocol for escape room 2.0 prop
5. Compatible hardware
6. Advantages of Arduino Yún and Dragino Yún shield
7. Advantages of the ArduinoProps library
8. Limitations due to PubSubClient
9. Examples

ArduinoProps library documentation
This README file
Introduction to Arduino Props
Arduino Prop sketch
Prop class reference
PropData class reference
PropAction class reference
ArduinoProps library examples
WiFiNINA firmware update

1. Installation and usage

Prepare Arduino IDE

Download ArduinoProps.zip from GitHub and use Sketch > Include Library > Add .ZIP Library...

Download library dependencies for Library Manager:

• PubSubClient
• ListLib

Add Dragino Yún + Mega 2560 board to Arduino IDE boards manager

If you are using Arduino Mega 2560 with Dragino Yún shield, add package_dragino_yun_test_index.json to Additional Boards Manager URLs in Preferences:

URL to add: http://www.dragino.com/downloads/downloads/YunShield/package_dragino_yun_test_index.json

Then install Dragino Yún in Boards Manager:

Learn more at Automatically Add Board Profile in Arduino IDE in Dragino Wiki.

Add the STM32 boards to the Boards Manager:

Open Preferences, in Settings tab, complete the Additionnal Boards Manager URLs with:

https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json

Then open the Boards Manager in Tools:

Find STM32 Cores by STMicroelectronics, Select version (latest) and Install:

In Library Manager, find STM32 libraries and install what you need:

• STM32duino Examples
• STM32duino LwIP
• STM32duino STM32Ethernet

Start coding your own prop

Add #include "ArduinoProps.h" on top of your sketch and start coding.

A fork of one the examples is the fastest way to create your own prop.

Arduino Yún an Dragino Yún shield setup

If you are not familiar with Yún (a Linux SoC bridged to the MCU), you will find help:

• Arduino Yún Board Setup and Demo at Medium
• Getting Started with the Arduino Yún at arduino.cc
• Getting Started With Arduino Yún - Video tutorial on YouTube

Find help in the documentation

Reading EXAMPLES.md will be helpful.

2. Escape room 2.0 prop with Arduino

The ArduinoProps library allows to build escape room 2.0 prop easily with Arduino and particularly with Arduino Yún or Arduino Mega 2560 + Dragino Yún shield however it works with Ethernet and Wifi shields too.

The ArduinoProps library relies on Nick O'Leary PubSubClient library for MQTT. MQTT is a lightweight publish/subscribe messaging protocol designed for M2M (machine to machine) telemetry in low bandwidth environments.

Props with Raspberry

Escape room 2.0 prop can be powered with Raspberry Pi or any Pythonic nanocomputer using MqttApp, our pure Python 3 class based on Eclipse Paho™ MQTT Python Client.

You will find Raspberry Pi libraries for escape room 2.0 prop at https://github.com/fauresystems, to build prop with RPi.GPIO, Pi Hats, Guizero, Pygames, PyQt5 or Kivi.

3. ArduinoProps library value for escape room 2.0

Nick O'Leary PubSubClient library is sufficient to write escape room 2.0 prop Arduino code.

The ArduinoProps library relies on Nick O'Leary PubSubClient for MQTT messaging and provides a framework and protocol for helping and accelerating the coding of Arduino prop. If you will help build simple and complex prop with reliable code.

Since 2016, ArduinoProps library is used extensively in many escape rooms with up to 20 prop per room (which is no limit at all), with a high level of availability and sustainability.

Inbox/oubox messaging

Instead of usual MQTT topic structure which sends every data value in a different topic for every variable, ArduinoProps library sends data via a unique outbox topic.

Prop receives commands in its inbox MQTT topic.

Prop can subscribe to any other MQTT topic to receive othe information, for example the escape game scenario (English/French/Kids) or the game clock countdown.

Escape room structured MQTT topics

If you're running our Escape Room control software Room 2.0 to supervise the escape room in real-time you have to respect its syntax for inbox/outbnox MQTT topics:

Room/[escape room name]/Props/[props name]/inbox|outbox

example:
    Room/Demoniak/Props/Arduino Contrôleur/inbox
    Room/Demoniak/Props/Arduino Contrôleur/outbox

MQTT supports UTF-8 encoding.

Sending messages only when appropriate

Usually Arduino IoT sketches send MQTT data for every variable at every loop. When the loop is fast, you can get tons of useless messages, and usually a sleeping delay is added at every loop to slow down the message flow ; this can slow down significantly the prop response time to human supervision and automation commands.

While Arduino sketch is sending a message it isn't doing prop sensor/actuator processing, and it takes about 20 to 40 milliseconds to send a message. With too many messsages it's too much processing time wasted.

ArduinoProps library sends all data periodically every 30 seconds (default parameter) and sends data changes over a period of time you choose (typical 400 milliseconds for real-time behavior, but you may choose every 100 milliseconds, 1 or 3 seconds: your choice for your application).

Therefore the minimum processing time is used to send messages.

Tracking data changes could make Arduino code difficult to read and maintain but the. ArduinoProps library will hide this mechanism and make the code much more readable.

Some analog data can change at every loop but not significantly, for example U=2.77 volts while showing this when it changes more than 10% could be sufficient. ArduinoProps library offers a nice syntax to take care of this significance, with simple code.

Maintaining MQTT server connection

MQTT connection state must be checked at erevy sketch loop as well as incoming MQTT messages. ArduinoProps library does all in one code line.

And on Yún this same code line can switch MQTT server IP address (can be helpful in a fallback plan).

Simple human-readable text protocol

An escape room 2.0 is typically centrally controlled from a Windows PC which provides the Game Master with monitoring and control information as well as some automation.

To unifiy escape room 2.0 development, ArduinoProps library provides a simple protocol between prop and room controller at application level:

    DATA -> send variables to control
    MESG -> send text to display in control
    DONE -> acknowledge that a command has been performed
    OMIT -> acknowledge that a command has been ignored
    OVER -> notify that a challenge is over
    REQU -> request a command to another prop
    PROG -> request a control program

Handling long message seamlessly and efficiently

MQTT standard limitations are far above what we need:

• maximum topic length 65,536 bytes (64k)
• maximum message size 268,435,456 bytes (256M)

However, on Arduino the limit is for the addition of topic length + message length:

• Wifi shield limit is 80 bytes
• Yún limit (due to Bridge) is 120 bytes

DATA messages when many I/O like on Arduino Mega 2560 and MESG information messages can go very long, and crash the sketch without notice at run-time.

ArduinoProps library seamlessly splits long messages smartly when required.

4. Application protocol for escape room 2.0 prop

A level 7 protocol (application level) is necessary for connected prop to report data and to be controlled for the escape room automation and game play.

We have defined a simple human-readable text protocol. Messages are encoded in UTF-8, in Arduino sketches use:

    str = u8"la chaîne avec des caractères non Latin1";

Messages are sent/received thru outbox/inbox MQTT topics:

    Room/[escape room name]/Props/[props name]/inbox
    Room/[escape room name]/Props/[props name]/outbox

Prop connection state is handled in the outbox topic:

• with a DISCONNECTED Will when MQTT server connection is broken
• with a CONNECTED retained message when MQTT server connection is established.

More MQTT topics can be use for anything (room scenario, etc.).

Messages sent from the Arduino prop are formatted

    DATA sensor=24.26 light=on challenge=pinball
    MESG Warning: sensor not detected
    DONE power:1
    OMIT power:1
    OVER pinball
    REQU Arduino Relay -> door:open
    PROG audio-final:start

Message received by the Arduino prop have no particular format

    power:1                  for example to power on the room 
    porte-salon:ouvrir       for example to open a door
    lumière-salon:éteindre   for example to switch-off a light

@PING-PONG special messages

    @PING is received in inbox then the prop sends just PONG in outbox
    -> so the escape room controller can monitor response time at application level

5. Compatible hardware

ArduinoProps library supported harware:

• Arduino Yún and Arduino Yún Rev 2
• Any Arduino + Dragino Yún Shield (tested with Elegoo Mega 2560 R3)
• Arduino Uno WiFi Rev 2
• Arduino NANO 33 IoT
• Arduino MKR WiFi 1010
• Arduino MKR VIDOR 4000
• Any Arduino + Ethernet Shield
• Any STM32 Nucleo-144 (tested with STM32-F767ZI)
  • Nucleo-144 boards have on-board Ethernet RJ45
  • STM32-H7xx not supported (STM32duino/STM32Ethernet limitation)

For WiFi prop, please update the WiFiNINA firmware: WiFiNINA firmware update.

To use other WiFi hardware compatible with any Nick O'Leary PubSubClient library you have to fork WifiProp.h and WifiProp.cpp and to replace WiFiNINA.h with appropriate WiFi library (ESP8266WiFi.h for example):

• Arduino WiFi Shield
• Sparkfun WiFly Shield – library
• TI CC3000 WiFi - library
• Intel Galileo/Edison
• ESP8266
• ESP32

6. Advantages of Arduino Yún and Dragino Yún shield

In escape room 2.0, prop are usually powered by Arduino Yún or Arduino Mega 2560 + Dragino Yún shield (or Raspberry Pi) because they are cheap and appropriate for DIY projects.

The advantage of Yún versus Ethernet/Wifi shields is that you can upload sketches remotely to the micro-controller during the whole prop lifetime (no need to open boxes and break walls to plug an USB cable when a sketch modification is required).

Arduino Mega 2560 + Dragino Yún shield offers much more memory and many more pins thann an Arduino Yún for same price.

See Dragino Yún Shield Wiki.

7. Advantages of the ArduinoProps library

You can build escape room 2.0 Arduino-based prop just with Nick O'Leary PubSubClient library for MQTT.

With ArduinoProps library:

• create connected prop quickly thanks to the application protocol and examples
• targetted for escape room prop, ArduinoProps library can be used for any IoT project
• re-use your code when creating new escape rooms
• rely on ArduinoProps library robustness: for example, the library handles the Arduino Yún Bridge transfer size limitation by smartly splitting large messages (only) when necessary.

Note: sending too large messages to Arduino Bridge breaks the Arduino sketch. ArduinoProps library prevents this crash case.

ArduinoProps library itself relies on Nick O'Leary PubSubClient library for MQTT.

8. Limitations due to PubSubClient

These limitations are not an issue for escape room prop:

• It can only publish QoS 0 messages.
• It can subscribe at QoS 0 or QoS 1.
• The keepalive interval is set to 15 seconds by default. This is configurable via MQTT_KEEPALIVE in PubSubClient.h.
• The client uses MQTT 3.1.1 by default. It can be changed to use MQTT 3.1 by changing value of MQTT_VERSION in PubSubClient.h.

9. Examples

The library comes with a number of example sketches. See File > Examples > ArduinoProps within the Arduino IDE application.

See EXAMPLES.md for an adaptation of the Blink example (https://www.arduino.cc/en/tutorial/blink) as a simple MQTT prop:

1. BlinkOnBridgeProp: the Blink example on a Yún prop with ArduinoProps library
2. BlinkOnEthernetProp: the Blink example on an Ethernet prop with ArduinoProps library
3. BlinkOnWifiProp: the Blink example on a Wifi prop with ArduinoProps library
4. BlinkOnBridgePubSub: the Blink example on prop using PubSubClient directly

Author

Faure Systems (Jun 26th, 2020)

• company: FAURE SYSTEMS SAS
• mail: dev at faure dot systems
• github: fauresystems
• web: Faure Systems