For this project we are assuming, that you have a Visual Basic .NET development environment set up and that you have a rudimentary understanding of the Visual Basic .NET language.
If you are totally new to Visual Basic .NET itself you should start here. If you are new to the Tinkerforge API, you should start here.
We are also assuming that you have a smoke detector connected to an Industrial Digital In 4 Bricklet as described here.
We are setting the following goal for this project:
Since this project will likely run 24/7, we will also make sure that the application is as robust towards external influences as possible. The application should still work when
In the following we will show step-by-step how this can be achieved.
To start off, we need to define where our program should connect to:
Const HOST As String = "localhost"
Const PORT As Integer = 4223
If the WIFI Extension is used or if the Brick Daemon is running on a different PC, you have to exchange "localhost" with the IP address or hostname of the WIFI Extension or PC.
When the program is started, we need to register the EnumerateCallback
callback and the Connected
callback and trigger a first
enumerate:
Sub Main()
ipcon = New IPConnection()
ipcon.Connect(HOST, PORT)
AddHandler ipcon.EnumerateCallback, AddressOf EnumerateCB
AddHandler ipcon.Connected, AddressOf ConnectedCB
ipcon.Enumerate()
End Sub
The enumerate callback is triggered if a Brick gets connected over USB or if
the Enumerate()
function is called. This allows to discover the Bricks and
Bricklets in a stack without knowing their types or UIDs beforehand.
The connected callback is triggered if the connection to the WIFI Extension or to the Brick Daemon got established. In this callback we need to trigger the enumerate again, if the reason is an auto reconnect:
Sub ConnectedCB(ByVal sender As IPConnection, ByVal connectedReason as Short)
If connectedReason = IPConnection.CONNECT_REASON_AUTO_RECONNECT Then
ipcon.Enumerate()
End If
End Sub
An auto reconnect means, that the connection to the WIFI Extension or to the Brick Daemon was lost and could subsequently be established again. In this case the Bricklets may have lost their configurations and we have to reconfigure them. Since the configuration is done during the enumeration process (see below), we have to trigger another enumeration.
Step 1 put together:
Module SmokeDetector
Const HOST As String = "localhost"
Const PORT As Integer = 4223
Sub ConnectedCB(ByVal sender As IPConnection, ByVal connectedReason as Short)
If connectedReason = IPConnection.CONNECT_REASON_AUTO_RECONNECT Then
ipcon.Enumerate()
End If
End Sub
Sub Main()
ipcon = New IPConnection()
ipcon.Connect(HOST, PORT)
AddHandler ipcon.EnumerateCallback, AddressOf EnumerateCB
AddHandler ipcon.Connected, AddressOf ConnectedCB
ipcon.Enumerate()
End Sub
End Module
During the enumeration we want to configure the Industrial Digital In 4 Bricklet. Doing this during the enumeration ensures that the Bricklet gets reconfigured if the Brick was disconnected or there was a power loss.
The configurations should be performed on first startup
(ENUMERATION_TYPE_CONNECTED
) as well as whenever the enumeration is
triggered externally by us (ENUMERATION_TYPE_AVAILABLE
):
Sub EnumerateCB(ByVal sender As IPConnection, ByVal uid As String, _
ByVal connectedUid As String, ByVal position As Char, _
ByVal hardwareVersion() As Short, ByVal firmwareVersion() As Short, _
ByVal deviceIdentifier As Integer, ByVal enumerationType As Short)
If enumerationType = IPConnection.ENUMERATION_TYPE_CONNECTED Or _
enumerationType = IPConnection.ENUMERATION_TYPE_AVAILABLE Then
We configure the Industrial Digital In 4 Bricklet to call the InterruptCB
callback if a change of the voltage level on any input pin is detected. The
debounce period is set to 10s (10000ms) to avoid being spammed with callbacks.
Interrupt detection is enabled for all inputs (15 = 0b1111).
If deviceIdentifier = BrickletIndustrialDigitalIn4.DEVICE_IDENTIFIER Then
brickletIndustrialDigitalIn4 = New BrickletIndustrialDigitalIn4(UID, ipcon)
brickletIndustrialDigitalIn4.SetDebouncePeriod(10000)
brickletIndustrialDigitalIn4.SetInterrupt(15)
AddHandler brickletIndustrialDigitalIn4.Interrupt, AddressOf InterruptCB
End If
Step 2 put together:
Sub EnumerateCB(ByVal sender As IPConnection, ByVal uid As String, _
ByVal connectedUid As String, ByVal position As Char, _
ByVal hardwareVersion() As Short, ByVal firmwareVersion() As Short, _
ByVal deviceIdentifier As Integer, ByVal enumerationType As Short)
If enumerationType = IPConnection.ENUMERATION_TYPE_CONNECTED Or _
enumerationType = IPConnection.ENUMERATION_TYPE_AVAILABLE Then
If deviceIdentifier = BrickletIndustrialDigitalIn4.DEVICE_IDENTIFIER Then
brickletIndustrialDigitalIn4 = New BrickletIndustrialDigitalIn4(UID, ipcon)
brickletIndustrialDigitalIn4.SetDebouncePeriod(10000)
brickletIndustrialDigitalIn4.SetInterrupt(15)
AddHandler brickletIndustrialDigitalIn4.Interrupt, AddressOf InterruptCB
End If
End If
End Sub
Now we need to react on the alarm signal of the smoke detector. But we want to
react only if the LED is turned on, not if it is turn off. This is done by
checking valueMask
for being > 0
. In that case there is a voltage
applied to at least one input, therefore, the LED is on.
Sub InterruptCB(ByVal sender As BrickletIndustrialDigitalIn4, _
ByVal interruptMask As Integer, ByVal valueMask As Integer)
If valueMask > 0 Then
System.Console.WriteLine("Fire! Fire!")
End If
End Sub
That's it. If we would copy these three steps together in one file and execute it, we would have a working program that reads the alarm status of a hacked smoke detector and reacts on its alarm signal!
Currently the program just outputs a warning. There are several ways to extend this. For example, the program could send an email or a text message to notify someone about the alarm.
However, we do not meet all of our goals yet. The program is not yet robust enough. What happens if it can't connect on startup? What happens if the enumerate after an auto reconnect doesn't work?
What we need is error handling!
On startup, we need to try to connect until the connection works:
while True
Try
ipcon.Connect(HOST, PORT)
Exit While
Catch e As System.Net.Sockets.SocketException
System.Console.WriteLine("Connection Error: " + e.Message)
System.Threading.Thread.Sleep(1000)
End Try
End While
and we need to try enumerating until the message goes through:
while True
try
ipcon.Enumerate()
Exit While
Catch e As NotConnectedException
System.Console.WriteLine("Enumeration Error: " + e.Message)
System.Threading.Thread.Sleep(1000)
End Try
End While
With these changes it is now possible to first start the program and connect the Master Brick afterwards.
We also have to deal with errors during the initialization:
If deviceIdentifier = BrickletIndustrialDigitalIn4.DEVICE_IDENTIFIER Then
Try
brickletIndustrialDigitalIn4 = New BrickletIndustrialDigitalIn4(UID, ipcon)
brickletIndustrialDigitalIn4.SetDebouncePeriod(10000)
brickletIndustrialDigitalIn4.SetInterrupt(15)
AddHandler brickletIndustrialDigitalIn4.Interrupt, AddressOf InterruptCB
System.Console.WriteLine("Industrial Digital In 4 initialized")
Catch e As TinkerforgeException
System.Console.WriteLine("Industrial Digital In 4 init failed: " + e.Message)
brickletIndustrialDigitalIn4 = Nothing
End Try
End If
Additionally we added some logging. With the logging we can later find out what exactly caused a potential problem.
For example, if we connect to the Master Brick via Wi-Fi and we have regular auto reconnects, it likely means that the Wi-Fi connection is not very stable.
That's it! We are already done with our hacked smoke detector and all of the goals should be met.
Now all of the above put together (download):
Imports Tinkerforge
Module SmokeDetector
Const HOST As String = "localhost"
Const PORT As Integer = 4223
Private ipcon As IPConnection = Nothing
Private brickletIndustrialDigitalIn4 As BrickletIndustrialDigitalIn4 = Nothing
Sub InterruptCB(ByVal sender As BrickletIndustrialDigitalIn4, _
ByVal interruptMask As Integer, ByVal valueMask As Integer)
If valueMask > 0 Then
System.Console.WriteLine("Fire! Fire!")
End If
End Sub
Sub EnumerateCB(ByVal sender As IPConnection, ByVal uid As String, _
ByVal connectedUid As String, ByVal position As Char, _
ByVal hardwareVersion() As Short, ByVal firmwareVersion() As Short, _
ByVal deviceIdentifier As Integer, ByVal enumerationType As Short)
If enumerationType = IPConnection.ENUMERATION_TYPE_CONNECTED Or _
enumerationType = IPConnection.ENUMERATION_TYPE_AVAILABLE Then
If deviceIdentifier = BrickletIndustrialDigitalIn4.DEVICE_IDENTIFIER Then
Try
brickletIndustrialDigitalIn4 = New BrickletIndustrialDigitalIn4(UID, ipcon)
brickletIndustrialDigitalIn4.SetDebouncePeriod(10000)
brickletIndustrialDigitalIn4.SetInterrupt(15)
AddHandler brickletIndustrialDigitalIn4.Interrupt, AddressOf InterruptCB
System.Console.WriteLine("Industrial Digital In 4 initialized")
Catch e As TinkerforgeException
System.Console.WriteLine("Industrial Digital In 4 init failed: " + e.Message)
brickletIndustrialDigitalIn4 = Nothing
End Try
End If
End If
End Sub
Sub ConnectedCB(ByVal sender As IPConnection, ByVal connectedReason as Short)
If connectedReason = IPConnection.CONNECT_REASON_AUTO_RECONNECT Then
System.Console.WriteLine("Auto Reconnect")
while True
Try
ipcon.Enumerate()
Exit While
Catch e As NotConnectedException
System.Console.WriteLine("Enumeration Error: " + e.Message)
System.Threading.Thread.Sleep(1000)
End Try
End While
End If
End Sub
Sub Main()
ipcon = New IPConnection()
while True
Try
ipcon.Connect(HOST, PORT)
Exit While
Catch e As System.Net.Sockets.SocketException
System.Console.WriteLine("Connection Error: " + e.Message)
System.Threading.Thread.Sleep(1000)
End Try
End While
AddHandler ipcon.EnumerateCallback, AddressOf EnumerateCB
AddHandler ipcon.Connected, AddressOf ConnectedCB
while True
try
ipcon.Enumerate()
Exit While
Catch e As NotConnectedException
System.Console.WriteLine("Enumeration Error: " + e.Message)
System.Threading.Thread.Sleep(1000)
End Try
End While
System.Console.WriteLine("Press key to exit")
System.Console.ReadLine()
ipcon.Disconnect()
End Sub
End Module