EL-USB-RT API Guide V1.0

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1 EL-USB-RT API Guide V1.0 Contents 1 Introduction 2 C++ Sample Dialog Application 3 C++ Sample Observer Pattern Application 4 C# Sample Application 4.1 Capturing USB Device Connect \ Disconnect Events 5 VB.NET Sample Application EL-USB-RT API Guide Page 1 of 10 Issue 1

1 Introduction This guide provides details of how to monitor the current temperature and humidity values of the EL- USB-RT data logger using the supplied dlls.

2 1 Introduction This guide provides details of how to monitor the current temperature and humidity values of the EL- USB-RT data logger using the supplied dlls. Four example applications are available: two built in C++, one in C# and one in VB.NET. 2 C++ Sample Dialog Application The C++ Sample Dialog application is in a folder called ELUSBRTDLLUsingCpp. The top level folder contains the Visual Studio solution file ELUSBRTDLL.sln. This is an MFC Dialog application with a single button called Get Data. Pressing this button will display the temperature and humidity values read from the EL-USB-RT device, the Dew point is calculated using the values read from the device. Building and running this sample application invokes the dialog shown below: In order to connect to the EL-USB-RT device from your own C++ applications, carry out the following actions: Copy the following DLLs from the sample application Debug\Release folder into your projects Debug\Release folders: ELUSBRTDLL.lib ELUSBRTLib.dll ELUSBRTDLL.dll In your project invoke the Property Pages dialog via the Project\<application name> Properties menu option. EL-USB-RT API Guide Page 2 of 10 Issue 1

screen shot below: 2) Set the relative path or full path of the ELUSBRTDLL.

3 1) Set the ELUSBRTDLL.lib in the Additional dependencies file under the Linker Input tab property as shown in the screen shot below: 2) Set the relative path or full path of the ELUSBRTDLL.dll directory in Additional include Directories under the C/C++ tab and also in the Additional Library Directory under the Linker tab General property: EL-USB-RT API Guide Page 3 of 10 Issue 1

4 The ELUSBRTDLL.dll exposes the method bool GetDataFromDevice(double* Temperature, int* Humidity) which gets the current temperature and humidity values, it returns True if the device is connected and False, when device is not connected. To use this method define the following external import declaration: extern "C" declspec(dllimport) bool GetDataFromDevice(double*, int*); 3 C++ Sample Observer Pattern Application This is a Console application that demonstrates how to continuously monitor the temperature and humidity values from a EL-USB-RT device at one second intervals using an Observer Pattern. The Observer Pattern is a mechanism whereby a subject (in this case the EL-USB-RT device) notifies observers (Client applications that have subscribed to it) of events, by calling their update() method Building and running this sample application will display the following console window: The temperature and humidity values from the EL-USB-RT device are updated at one second intervals. EL-USB-RT API Guide Page 4 of 10 Issue 1

5 To implement this functionality in your own application carry out the following actions: 1) Create a console application project. 2) Copy the DLLs from this sample into your own project and link them in as described in the C++ Dialog Sample application. 3) Copy the file BaseApp.h into your project and include it in the Header Files folder. 4) In your application header file and the following code: #include "BaseApp.h" using namespace ELUSBRTClientDLL; // Export funtions for attaching and detaching the application extern "C" declspec(dllimport) void RegisterWindowHandle(UsingApplication*); extern "C" declspec(dllimport) void UnRegisterWindowHandle(UsingApplication*); 5) Base your application on UsingApplication defined in the BaseApp.h file as shown below: // Application class inherits the UsingApplication(declared in ELUSBRTDLL.dll) class CMyApplication : public UsingApplication 6) Implement the following Update() method in your application (this is a virtual method defined in the base class UsingApplication ) in order to receive temperature and humidity updates on a regular basis. // Called by the ELUSBRTDLL at one second intervals void Update(double temperature, int humidity) m_dtemprature = temperature; m_nhumidity = humidity; 7) When your application starts call RegisterWindowHandle as follows to subscribe for update events: RegisterWindowHandle(this); 8) When your application exits call UnRegisterWindowHandle as shown below to unsubscribe for update events: UnRegisterWindowHandle(this); EL-USB-RT API Guide Page 5 of 10 Issue 1

4 C# Sample Application The C# sample application is in a folder called ELUSBRTDLLUsingCSharp. The top level folder contains the Visual Studio solution file ELUSBRTDLLUsingCSharp.sln.

6 4 C# Sample Application The C# sample application is in a folder called ELUSBRTDLLUsingCSharp. The top level folder contains the Visual Studio solution file ELUSBRTDLLUsingCSharp.sln. Building and running this sample application invokes the following dialog. Pressing the Get Data button will display the current Temperature, Humidity and Dew Point values. (note: Dew Point is a derived value). When the Monitor check box is checked the EL_USB_RT values will be continually monitored. In order to connect to the EL-USB-RT device from your own C# applications, carry out the following actions: 1) Copy the ELUSBRTLib.DLL (located in the C# demo application subfolder ELUSBRTDLL) into your own project folder. 2) Add a reference to the ELUSBRTLib.dll in your project as follows: Right-click on the folder References and choose the context menu option Add Reference choose the Browse tab, select the ELUSBRTLib.DLL copied into your project and press OK. 3) Add the components namespace reference. using EL_USB_RT_USBLib; EL-USB-RT API Guide Page 6 of 10 Issue 1

7 The following code snippet demonstrates how to create an EL-USB-RT device component and register for connect and disconnect events in C#: try // Create component used to communicate with the EL-USB-RT device m_usbcomponent = new USBHidComponent(this.components); // Hook into the connect and disconnect events m_usbcomponent.onelusbrtdeviceconnected += new EventHandler(this.OnDeviceConnected); m_usbcomponent.onelusbrtdevicedisconnected += new EventHandler(this.OnDeviceDisconnected); // Register with the component m_usbcomponent.registerwindowshandle((intptr)this.handle); m_initialised = true; catch (Exception ex) MessageBox.Show("Failed to create USB Component" + ex.message); private void OnDeviceConnected(object sender, EventArgs e) m_devicestatus = true; private void OnDeviceDisconnected(object sender, EventArgs e) m_devicestatus = false; EL-USB-RT API Guide Page 7 of 10 Issue 1

8 The following method demonstrates how to read temperature and humidity from the device. private void GetDataFromUSBDevice() try double temptemp = -300; byte temphumid = 200; int counter = 0; while (true) m_usbcomponent.getdatafromdevice(ref temptemp, ref temphumid); if ((temptemp >= -10 && temptemp <= 60) && (temphumid >= 0 && temphumid <= 100)) Temperature = temptemp; Humidity = temphumid; break; if (counter++ > 25) throw new Exception(); catch (Exception ex) MessageBox.Show("Failed to get data from USB Component" + ex.message); EL-USB-RT API Guide Page 8 of 10 Issue 1

9 4.1 Capturing USB Device Connect \ Disconnect Events Whenever the USB Device is removed or inserted, a Windows message is generated. It is necessary for your application to update the USB Component with these messages in order for the Connect and Disconnect event triggers to function correctly. To capture the Windows messages required to update the USB Component, add the following override to your applications form: /// <summary> /// Overriding WndProc to handle messages related to USB device /// connection and disconnection /// </summary> protected override void WndProc(ref Message m) try if (m_initialised) // Parse message for Device connection\disconnection m_usbcomponent.processmessages(ref m); // Pass message on to base form base.wndproc(ref m); catch (Exception) Alternatively a timer can used to periodically poll the USB Device to detect if the device is connected or disconnected, below is an example of timer event handler used to trigger connect and disconnect events on the USB Device component: /// <summary> /// Timer tick event handler /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void usbtimer_tick(object sender, EventArgs e) usbtimer.enabled = false; try if (m_initialised) // Poll for connection status m_usbcomponent.checkforelusbrtdevice(); catch (Exception) usbtimer.enabled = true; EL-USB-RT API Guide Page 9 of 10 Issue 1

10 5 VB.NET Sample Application The VB.NET sample application is in a folder called ELUSBRTDLLUsingVB. This is the same application as the C# project, converted to VB format. EL-USB-RT API Guide Page 10 of 10 Issue 1

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