Open you brain,
Discussion about DBPC can take place here.
I would like to help to develop DBPC. Can we have a mailling list for it? LuisMatos
about DBPC server
- plugin driven development: dbpc server only provides a way to achieve communication. It does not provides one.;
- it must be lightweight so it can be used for in any kind of embedded system;
- it has to have control over communication with the plugins, so that the communication can be organized (request for a bunch of data once, instead of a lots of connections and low data).;
- have an event driven api, so that the clients don't ask for changed data, but the server provides the changed data.; LuisMatos
Not sure about what you mean. I imagine a server more like a daemon than a plugin..?
Yes, no problem, Dbus is lightweight enough.
Yes, it is better fetching an array than one request for each bit. Server must also have methods for control its behavior and troubleshooting.
Yes it must be a fine if servers may pool PLC values only when there is a subscription to the corresponding item and return events when values changed. D-BUS is event based, so DBPC client can easily subscribe to DBPC events. Nevertheless I did not find a way to inform the server about event subscription and release. DBus Events seems to be only some kind of broadcast.
As an optimization we should pool PLC values only when needed. DBPC server can act like a proxy. If several applications access to the same item at the same time, we will not update item value every time but only if value is outdated.
Rey Cyril 23.06.2009
"Not sure about what you mean. I imagine a server more like a daemon than a plugin..?"
DBPC is a daemon, but it only manages data and connections. connection types and data getting must be managed by plugins. For example, one DBPC server, plugin for modbus, profibus, etc
or ... a XML file?
bad, bad example:
* <source name="controller1" plugin="modbus" > * <param1>192.168.0.1</param>
* <tag source="controller1" tagname="tag" address="M101.0" type="bit"/>
grep tag : returns all tag names grep source: all sources grep tag, remove all names and " you can get an array of tagname, address and datatype.