Introduction

This guide demonstrates the usage of NMEAOnSerial component in a Linux environment to receive arbitrary data from a command line over a virtual serial connection using CDP Studio, the independent automation software for open PC-based real-time distributed control systems. To use NMEAOnSerial successfully without virtual connections, a serial loopback device or an actual NMEA capable device must be attached to the configured serial port. In this example, a Socat utility program is used to create two virtual serial connections.

Creating Virtual Connections

First, two virtual connections have to be created – one for sending data from terminal and another one for NMEAOnSerial component to receive the data.

• Install Socat utility program. More information about Socat can be found here
• Open the terminal and type

  socat pty,link=/tmp/CDPCOM0,raw,echo=0 pty,link=/tmp/CDPCOM1,raw,echo=0

• Leave the terminal open for the testing period
• A similar view should be seen in the terminal

  

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 NMEAOnSerial Component

• Click on the default application called NMEATestApp
• Click on NMEA0183IO to expand its contents in the Resource tree
• Choose NMEAOnSerial component and add it to the default application

  

Adding ReceiveData To NMEAOnSerial and Configuring It

• Double-click on the NMEAOnSerial that was added
• Double-click the SerialTransport to navigate into it
• Set the ComPort Value to /tmp/CDPCOM0
• Select the NMEAOnSerial component in the Project tree
• From the Resource tree, double-click ReceiveData inside the NMEA0183IO resource to add it to NMEAOnSerial
• Double-click Receive to navigate into it
• Tick DisableChecksum. We want this disabled to simplify testing with random data
• Set Header to $T. Anything starting with $T, will now be accepted
• From the NMEA0183IO resource in the Resource tree, double-click a String resource to add it

  

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.

Testing the System

• Navigate into NMEATestApp NMEAOnSerial Receive
• Open another terminal and type

  echo '$T,My first message' > /tmp/CDPCOM1

• Watch how the data appears in the Text Value column