20,741
edits
Generic protocol: Difference between revisions
Jump to navigation
Jump to search
→External links: add category {{PropertyTree}}
m (→External links: typo) |
(→External links: add category {{PropertyTree}}) |
||
| Line 217: | Line 217: | ||
total package size: 17 bytes | total package size: 17 bytes | ||
</pre> | </pre> | ||
{{PropertyTree}} | |||
== Generic Protocol == | |||
FlightGear has an inbuilt "generic" protocol to push and pull data. (todo) | |||
To interface with FlightGear on a socket for example, the following steps need to be taken. | |||
# Establish which "properties" you want to appear "on the wire" | |||
# Create a my_protocol.xml file containing those properties | |||
# Start flight gear on a socket using my_protocol. | |||
For this simple example say were interested in heading and altitude, and we want to "listen" ie output to a socket at port 6789, udp and receiving 10 times a second in the format: | |||
alt\thead\n | |||
// ie altitude - tab - heading - newline | |||
The first step is establishing the nodes, in this example | |||
/position/altitude-agl-ft eg (22.4713923) | |||
/orientation/heading-deg eg (297.966325) | |||
Next create a file '''my_protocol.xml'''. This needs to be located at | |||
[[$FG_ROOT]]/Protocol/my_protocol.xml | |||
The XML looks like this: | |||
<?xml version="1.0"?> | |||
<PropertyList> | |||
<generic> | |||
<output> | |||
<line_separator>newline</line_separator> | |||
<var_separator>tab</var_separator> | |||
<chunk> | |||
<node>/position/altitude-agl-ft</node> | |||
<name>altitude to go</name> | |||
<type>float</type> | |||
<format>%03.2f</format> | |||
</chunk> | |||
<chunk> | |||
<node>/orientation/heading-deg</node> | |||
<name>Heading</name> | |||
<type>float</type> | |||
<format>%03.3f</format> | |||
</chunk> | |||
</output> | |||
</generic> | |||
</PropertyList> | |||
* The '''output''' tag indicates the protocol for output. The same "protocol" file can contain an "input" section, absent in this example (more later). | |||
* '''line_seperator''' - the end of line (todo ? is this \r\n??) | |||
* '''var_seperator''' - the delimiter for the properties, this could be "|", "###", any string. | |||
* The two '''chunk''' blocks contain our data. Note that these appear in the order presented within the xml file. | |||
** '''node''' - the node of data we want | |||
** '''name''' - it there for a reference, its not transmitted and note necessary (like a note) | |||
** '''type''' - the way this xml is to interpret the value. This is quite important tag. For example if its not there or a string, then "floats" go wild and end up being a string of 32 characters with two decimal places! | |||
** '''format''' - same syntax as printf | |||
** There's more that can be done {todo - link to a full blown example/reference} | |||
We can now start FlightGear and listen with: | |||
fgfs --generic=socket,out,10,localhost,6789,udp,my_protocol | |||
[todo] - link here to the tutorial | |||
== External links == | == External links == | ||
| Line 225: | Line 289: | ||
[[Category:Software]] | [[Category:Software]] | ||
[[Category:XML]] | [[Category:XML]] | ||
[[Category:Property Tree]] | |||