Introduction

This guide demonstrates usage of NMEAOnUDP to send and receive a GPS position telegram over the ethernet with CDP Studio, the independent automation software for open PC-based real-time distributed control systems.

Setting up a Test-system

First we set up a System that the component can be tested in:

Create a system named NMEATest with a Console application named NMEATestApp, then select Configure mode. See How to Create a system for more information.

Adding an NMEAOnUDP Component

• Select the NMEATestApp that resides under NMEATest in the Project tree
• Select the NMEA0183IO in the Resource tree
• Right-click on NMEAOnUDP and select Add

  

• Double-click the newly added NMEAOnUDP in the Block Diagram to navigate into it
• Double-click the NetworkTransport to navigate into it
• Set ListenPort to 5000
• Set RemoteIP to 127.0.0.1
• Set RemotePort to 5000

  

Sending NMEA Strings

Building up NMEA strings to send is done by creating a sequential list of signals and strings. These signals and strings correspond to the values in the NMEA string that are separated by commas. To send '$GPGLL,62.470000,N,6.145380,E':

• Select NMEAOnUDP in the Project tree
• Expand NMEA0183IO in the Resource tree and double-click SendData to add it to the selected component
• Double-click the Send node that was added to navigate into it
• Change SendData Header to '$GPGLL' to emulate the example above
• From the Resource tree, double-click Signal<double> to add it to the data to send
• Rename the added Signal in the CDPChannel table to 'Latitude'
• Set the Value to 62.470000
• From the Resource tree, Add a String and rename it to 'NorthSouth'
• Set the Value to 'N'
• Add a Signal<double> and rename it to 'Longitude'
• Set the Value to 6.145380
• Add a String and rename it to 'EastWest'
• Set the Value to 'E'
• The configuration should now look something like this:

  

Receiving NMEA Strings

Receiving NMEA strings is just as simple as sending them. Create a sequential list of signals and strings. The signals and strings correspond to the values in the NMEA string that are bounded by commas. To replicate the example above ($GPGLL,62.470000,N,6.145380,E*61):

• Make sure that the NMEAOnUDP component is selected in the Project tree, and that the IOConfig table is visible
• Double-click ReceiveData in the NMEA0183IO resource in the Resource tree to add it
• Double-click the newly added Receive to navigate into it
• Select Header. Change it to '$GPGLL' to emulate the example above
• In the NMEA0183 in the Resource tree, right-click and Add a Signal<double>
• Rename the newly added signal to 'Latitude'
• Add a String, rename it to 'NorthSouth'
• Add a Signal<double>, rename it to 'Longitude'
• Add a String and rename it to 'EastWest'

How to Run the Tutorial

To run the tutorial from CDP Studio, select Configure mode, right-click on the system project and select Run & Connect. See the Running and Connecting to the System tutorial for more information.

Verify That It Works

• Click into NMEATest.NMEATestApp.NMEAOnUDP.ReceiveData
• Observe that the values sent out match the ones that are received
• Go into NMEATest.NMEATestApp.NMEAOnUDP.SendData
• Change Latitude to 62.470597
• Change Longitude to 6.210851
• Click into NMEATest.NMEATestApp.NMEAOnUDP.ReceiveData
• Observe that the received values have changed
• Stop the system by Right-clicking the NMEATest in the Project tree and clicking Stop