Connect with a device¶

IoT Drivers allow any Juniper module to communicate in real-time with any device connected to the IoT Box. Communication with the IoT Box goes both ways, so the Juniper client can send commands to and receive information from any of the supported devices.

To add support for a device, all we need is:

an Interface, to detect connected devices of a specific type
a Driver, to communicate with an individual device

At each boot, the IoT Box will load all of the Interfaces and Drivers that can be located on the connected Juniper instance. Each module can contain an iot_handlers directory that will be copied to the IoT Box. The structure of this directory is the following

your_module
├── ...
└── iot_handlers
    ├── drivers
    │   ├── DriverName.py
    │   └── ...
    │
    └── interfaces
        ├── InterfaceName.py
        └── ...

Detect Devices¶

Devices connected to the IoT Box are detected through Interfaces. There is an Interface for each supported connection type (USB, Bluetooth, Video, Printers, Serial, etc.). The interface maintains a list of detected devices and associates them with the right Driver.

Supported devices will appear both on the IoT Box Homepage that you can access through its IP address and in the IoT module of the connected Juniper instance.

Interface¶

The role of the Interface is to maintain a list of devices connected through a determined connection type. Creating a new interface requires

Extending the Interface class
Setting the connection_type class attribute
Implementing the get_devices method, that should return a dictionary containing data about each detected device. This data will be given as argument to the constructors and supported method of the Drivers.

Note

Setting the _loop_delay attribute will modify the interval between calls to get_devices. By default, this interval is set to 3 seconds.

from Juniper.addons.hw_drivers.interface import Interface

class InterfaceName(Interface):
    connection_type = 'ConnectionType'

    def get_devices(self):
        return {
            'device_identifier_1': {...},
            ...
        }

Driver¶

Once the interface has retrieved the list of detected devices, it will loop through all of the Drivers that have the same connection_type attribute and test their respective supported method on all detected devices. If the supported method of a Driver returns True, an instance of this Driver will be created for the corresponding device.

Note

supported methods of drivers are given a priority order. The supported method of a child class will always be tested before the one of its parent. This priority can be adjusted by modifying the priority attribute of the Driver.

Creating a new Driver requires:

Extending Driver
Setting the connection_type class attribute.
Setting the device_type, device_connection and device_name attributes.
Defining the supported method

from Juniper.addons.hw_drivers.driver import Driver

class DriverName(Driver):
    connection_type = 'ConnectionType'

    def __init__(self, identifier, device):
        super(NewDriver, self).__init__(identifier, device)
        self.device_type = 'DeviceType'
        self.device_connection = 'DeviceConnection'
        self.device_name = 'DeviceName'

    @classmethod
    def supported(cls, device):
        ...

Communicate With Devices¶

Once your new device is detected and appears in the IoT module, the next step is to communicate with it. Since the box only has a local IP address, it can only be reached from the same local network. Communication, therefore, needs to happen on the browser-side, in JavaScript.

The process depends on the direction of the communication: - From the browser to the box, through Actions - From the box to the browser, through Longpolling

Both channels are accessed from the same JS object, the DeviceProxy, which is instantiated using the IP of the IoT Box and the device identifier.

var DeviceProxy = require('iot.DeviceProxy');

var iot_device = new DeviceProxy({
    iot_ip: iot_ip,
    identifier: device_identifier
});

Actions¶

Actions are used to tell a selected device to execute a specific action, such as taking a picture, printing a receipt, etc.

Note

It must be noted that no “answer” will be sent by the box on this route, only the request status. The answer to the action, if any, has to be retrieved via the longpolling.

An action can be performed on the DeviceProxy Object.

iot_device.action(data);

In your driver, define an action method that will be executed when called from an Juniper module. It takes the data given during the call as argument.

def action(self, data):
    ...

Longpolling¶

When any module in Juniper wants to read data from a specific device, it creates a listener identified by the IP/domain of the box and the device identifier and passes it a callback function to be called every time the device status changes. The callback is called with the new data as argument.

iot_device.add_listener(this._onValueChange.bind(this));

_onValueChange: function (result) {
    ...
}

In the Driver, an event is released by calling the device_changed function from the event_manager. All callbacks set on the listener will then be called with self.data as argument.

from Juniper.addons.hw_drivers.event_manager import event_manager

class DriverName(Driver):
    connection_type = 'ConnectionType'

    def methodName(self):
        self.data = {
            'value': 0.5,
            ...
        }
        event_manager.device_changed(self)