Hello,
your approach seems to point in the right direction. To avoid doubts let me recapitulate it:
Step 1: You add a new Control class.
This class should implement the interface between the GUI and the device. The simplest would be to use for this purpose the template Device Interface from the Gallery folder Device as demonstrated in the screenshot below. Just drag-and-drop it to one of your own project units:
Please note: with this template you get also an autoobject (a global instance of the interface class). This instance will be used wherever you want to access the interface.
Step 2: In your interface class implement a new property.
If you have created the interface class from the provided template (as explained in the step 1 above), the class contains already one property demonstrating this approach. The following is the screenshot of such class:
In this case you can use the already provided property. If desired you can rename it to e.g. ADCVALUE. As you see in the template the property is accompanied by it OnSet method and an additional UpdateProperty method. All other members within the class exist for demonstration purpose and is not relevant in your case. You can thus select and delete the members like TriggerEvent, SystemEvent, ...
If you want more properties in the interface, use the template Property from the Gallery folder Device as demonstrated in the screenshot below. This template is especially adapted to serve in interfaces:
Step 3: Connect the interface to e.g. Gauge:
Switch to your GUI component containing the Gauge, etc. widget you want to connect with the interface. Select the Gauge widget and in Inspector window look for its property Outlet. Activate the Assistant for this Outlet property and select the right interface property you want to connect the Gauge with. In this example, the property is named Property and it is a member of the global autoobject Application::Device.
Step 4: Generate code for your target device.
Step 5: Update the property value from your main application.
This is the point you have possibly doubts. How to feed the GUI application when the device receives new data?
Please recall the method UpdateProperty() mentioned in the step 2 above. Every time you call the method, the corresponding property is updated and a broadcast is sent to notify all the GUI components (e.g. the Gauge widget) about the value change. Thus all you have to do is to call the corresponding C function. The difficulty here: you have to call it in context of the same global autoobject you have connected the Gauge widget with (step 3 above).
The following is the necessary C code to perform the operation:
/* Obtain access to the global autoobject 'Application::Device' of the
class 'Application::DeviceClass' */
ApplicationDeviceClass device = EwGetAutoObject( &ApplicationDevice, ApplicationDeviceClass );
/* In context of the object invoke the method 'UpdateProperty' */
ApplicationDeviceClass__UpdateProperty( device, 25 );
That is all. More details are found in the documentation:
Device Class and Device Driver
Integrating with the device.
and
Connect the Gauge with a data provider
Important: The GUI application is not thread safe. If you are running an operating system, you should call the UpdateProperty() always in context of the thread driving the GUI itself.
This here presented approach is optimized to react to random value changes in the device. The functiopn UpdateProperty() is called only when the corresponding value changes (like a push notification). If you have an application case with the value changing permanently, you don't need to be notified from the device about every change. Instead you will need to update the Gauge periodically. Do following:
Step 6: Ignore the above steps 3, 4 and 5.
Step 7: If not existing yet add a new OnGet method to your device class (where you implement the interface).
The method should be named corresponding to the name of the property e.g. OnGetADCVALUE. Following is the screenshot demonstrating this step:
Step 7: Edit the OnGet method
Implement the method to query the ADC vallue and return it. The target specific C code is enclosed insoide the native statement. For example:
Step 8: Drive your GUI component to update the Gauge periodically.
Add a Timer object to the GUI component containing the Gauge widget. Configure the timer to e.g. expire every 100 ms. Add a slot method to your component and connect it to the OnTrigger property of the timer. In the slot method implement following code:
Don't forget to activate (enable) the timer.
Now with this approach, the Timer will cause the GUI component to query the latest ADC value 10 times per second and update the GUI component.
I hope it helps you further.
Best regards
Paul Banach
