Re: [Flightgear-users] FlightGear Generic Input Protocol Problem

[Conrad B. <fli...@sa...>]

Hi,
I found your message in the mailing list archive:

Brent Terwilliger wrote on Thu, 19 Jun 2008 13:42:44 -0700
> 
> I am trying to control several of FlightGear's internal options via the Generic 
> Input protocol, without success. I have been able to create a UDP Listener 
> application, setup an "Output block" in the XML protocol file, 
> and succesfully read the output string via UDP Socket from FlightGear. Now I 
> want to do the opposite and control these items using a Sender application and 
> defined input blocks in the protocol XML file. To simplify things I have only 
> attempted to write to the Longitude and Latitude position values. 
> 
> The following describes code I use in my UDP Sender app, a C# application, the 
> protocol XML file, and the command line arguments used to start FlightGear.
> 
> First, I developed a simple C# application that initializes a UDP Socket using 
> the following bit of code that is called once:
> 
> IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 
> int.Parse("5500"));
> Socket xmlServer = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, 
> ProtocolType.Udp);
> xmlServer.Connect(ipep);
> 
> Then a timer function calls the following bit of code every 100 milliseconds:
> 
> string templongitude = "-122.357246";
> string templatitude = "37.613544";
> string desiredDevider = ";";
> string tempString = templongitude + desiredDevider + templatitude + "\r";
> byte[] data = new byte[1028];
> data = Encoding.ASCII.GetBytes(tempString);
> xmlServer.Send(data);
> 
> The implmentation of these two pieces of code results in the following string 
> being sent to port 5500 on 127.0.0.1, every 100 milliseconds:
> "-122.357246;37.613544"
> 
> I have verified this using my aforemention UDP Listener application.
> 
> The following represents the "simpleLongLat_in.xml" file, that is used to 
> define the Long/Lat input "chunks":
> 
> <?xml version="1.0"?>
> <PropertyList>
> <generic>
> <input>
> <line_separator>\r</line_separator>
> <var_separator>;</var_separator>
>     <chunk>
>      <name>Longitude Degree</name>
>      <node>/position/longitude-deg</node>
>      <type>float</type>
>      <format>%f</format>
>     </chunk>  
>     <chunk>
>      <name>Latitude Degree</name>
>      <node>/position/latitude-deg</node>
>      <type>float</type>
>      <format>%f</format> 
>     </chunk>  
> </input>
> </generic>
> </PropertyList>
> 
> Finally, I begin my application and start broadcasting the data to port 5500, 
> on 127.0.0.1, then I open FlightGear with the following options:
>  --fdm=null
>  --model-hz=100
>  --generic=socket,in,100,127.0.0.1,5500,udp,simpleLongLat_in
> 
> FlightGear begins, and starts loading, upon reaching the "loading scenery" 
> mark, I get a "error reading data." message on the console window, that repeats 
> every 100 milliseconds. I've tried various combinations of formatting to the 
> XML file and to the outgoing text string without success (such as placing 
> "long=%f" in the <format> line of the XML file and the outgoing string). What 
> am I doing wrong?
> 
> The following represents the PC I'm running this on:
> Windows XP OS
> Pentium 4 CPU, 2.80GHz
> 1.0 GB RAM
> 
> While not a screaming machine, I can run FlightGear on this platform, without 
> major problems.
> 
> Thanks,
> 
> Brent A. Terwilliger

I'm having similar problems using the serial protocol.
In your specific case, what struck my eye was
>  --generic=socket,in,100,127.0.0.1,5500,udp,simpleLongLat_in
>
> FlightGear begins, and starts loading, upon reaching the "loading
> scenery" mark, I get a "error reading data." message on the console
> window, that repeats every 100 milliseconds.
wouldn't that mean you're asking Flightgear to poll the input with
100Hz, i.e. every ten milliseconds?

The timing appears to be very stringent, punishing even aberrations in 
the order of one millisecond.