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InnoRasPi2019

Innovation project by:

Aleksi Alatalo, Aldo Heino, Tuomas Paakkunainen, Joonatan Sohkanen, Visa Tuominen

The goal was to explore the Raspberry Pi as a teaching platform. Our group chose to work with Digi XBee3 devices using the Raspberry Pi to run python code to monitor and command the XBee devices.

Features of the program:

  • Monitor readings from sensors in the network, displayed in a dynamically created web interface.

  • Set DIO pins according to value limits set in configuration files:

    User can set limits for values in sensor configuration, and a sensor to trigger when this limit is met or exceeded. For example, you could monitor room humidity and hook up a room humidifier control.

Planned features not implemented:

  • Trigger configuration from web interface --> user configurable automation. This is currently achieved through editing deviceTypes file.
  • MORE controllable stuff! Only blinking leds gets boring fast.

The following Python 3 libraries were used:

  • digi-xbee: library for using XBee devices in API mode
  • Flask: web application framework for Python
  • Flask-SocketIO: socketIO extension for Flask. This enables real time communication between the web interface host and a connected client.

Other used stuff:

  • Bootstrap4: open source web development toolkit. Makes creating decent looking websites a bit easier
  • socketIO script on web interface for real time value updating

We used Visual Studio Code for writing and it has pretty good integration with git and some great extensions for our project:

XBClass

Instantiating masterXBee object & callback function

The master xbee object requires 3 arguments:

  • port: COMX or dev/ttyUSBX port of local xbee device set to FORM network in XCTU
  • baud: baud rate of local XBee
  • callback_handler: function to handle callbacks. Should take 2 arguments:
    • sensor (str): name of the sensor that the value comes from
    • value (str): the actual value (number, "HIGH" or "LOW")

For example:

def callbackFunction(sensor, value):
    print("Callback! Value from", sensor, ":", value)

master = masterXBee(port=COM8, baud=921600, callback_handler=callbackFunction)

devices dictionary

On startup, the masterXBee class creates a dictionary of all XBees and sensors in the network in the following format:

devices : {
    "DEVICE64BITADDRESS" : <XBeeDev object>
        sensors = {
            "DOORBELL_BUZZER"  : <XBeeSensor object>
            "LED_WGT"   : <XBeeSensor object>
            "LIGHT_SENSOR" <XBeeSensor object>
        }
    "SECOND64BITADDRESS" : <XBeedev object>
        sensors = {
            "WEIGHT_PLATE"  : <XBeeSensor object>
            "DOORBELL"   : <XBeeSensor object>
        }
    "SECOND
}

Reading and writing values

The masterXBee object has a method called general_io for reading and writing values. The first argument should bee an XBeeSensor object, the optional second argument should only be given when writing values to sensors:

# read value from WEIGHT_PLATE
wgtPlateVal = master.general_io(master.devices["SECOND64BITADDRESS"].sensors["WEIGHT_PLATE"])
# write HIGH to DOORBELL_BUZZER
master.general_io(master.devices["DEVICE64BITADDRESS"].sensors["DOORBELL_BUZZER"], "HIGH")

Polling sensor values

The masterXBee.start_polling(interval) method will start updating the sensor values to a dictionary masterXBee.sensordata with given interval:

# update sensor value data twice a second
master.polling_start(interval=0.5)

# stop polling!
master.polling_stop()

the sensordata dictionary format:

sensordata = {
    "DEVICE64BITADDRESS" : {
        "DOORBELL_BUZZER" : "LOW",
        "LED_WGT" : "HIGH",
        "LIGHT_SENSOR" : 869
    }
}

this format is readable by javascript at least when sent through flask-socketIO.

Registering callbacks

You might want to register callbacks for fast operation when some sensor changes value. User buttons are a good exapmle of this. We want to get the button press straight away instead of only getting value updates every second or so through polling.

# register callback with the device ID and list of sensor names you want to monitor for changes:
# instant updates from doorbell and weight plate:
master.register_callback("SECONDE64BITADDRESS", ["DOORBELL", "WEIGHT_PLATE"])

# only from doorbell:
master.register_callback("SECONDE64BITADDRESS", ["DOORBELL"])

# clear callbacks from device
master.register_callback("SECONDE64BITADDRESS", None)

Some links

XBee

Wireless xbee modules were used as the main component for the whole project.

Flask

Bootstrap