Skip navigation.
Home
The QNX Community Portal

View topic - multiple hosts connected via ethernet - still realtime?

multiple hosts connected via ethernet - still realtime?

For discussion of realtime and/or embedded programming.

multiple hosts connected via ethernet - still realtime?

Postby queBurro » Tue May 31, 2011 9:02 am

I'm planning on having multiple QNX hosts communicating over ethernet using IPC http://www.qnx.com/developers/docs/qnx_4.25_docs/qnx4/sysarch/microkernel.html#IPCNET.
Is this setup still realtime/deterministic? since I'll have messages going via a router (not realtime) and over ethernet? should I be looking at other forms of communication (CANbus etc.) or is ethernet ok as a physical medium but I'd need some kind of "industrial" router?
I'm assuming(maybe incorrectly) that it all works via TCP/IP?
queBurro
Active Member
 
Posts: 79
Joined: Fri Jul 30, 2010 2:05 pm

RE: multiple hosts connected via ethernet - still realtime?

Postby mario » Tue May 31, 2011 2:27 pm

Ethernet is NOT real-time nor deterministic but in most scenario is consider fast enough. Note that QNX4 native messaging is NOT routable.

Why are you looking at QNX4.25 instead of QNX6.5.0?
mario
QNX Master
 
Posts: 4132
Joined: Sun Sep 01, 2002 1:04 am

RE: multiple hosts connected via ethernet - still realtime?

Postby queBurro » Thu Jun 02, 2011 2:36 pm

I'm actually using 6.3.2 (but I can't find an online doc for 632) so I'm guessing this is the doc I should be looking at?
http://www.qnx.com/developers/docs/6.5. ... h/ipc.html

What I'm trying to do is MsgSend from one host to another host, only we're not sure how to do it, currently considering daisy chaining hosts together but also considering alternatives like ethercat etc. (http://www.openqnx.com/PNphpBB2-viewtopic-t10172-.html) -

anyone got any recommendations? cheers
---
Is MsgSend between Ethernet connected QNX hosts still tcp? Or does it go via its own realtime protocol?
queBurro
Active Member
 
Posts: 79
Joined: Fri Jul 30, 2010 2:05 pm

RE: multiple hosts connected via ethernet - still realtime?

Postby mario » Thu Jun 02, 2011 3:10 pm

QNX native messaging can run native or inside IP packet ( thus becoming routable ).

Ethernet at the wire level is not realtime, so no protocol can claim to be real-time/deterministic when run over ethernet.

To make any recommendation, one would need to have some more detail of your requirement. Real-time is in itself a pretty loose definition ;-)

As far as I know currently QNET or TCP/IP can only run over Ethernet I know of no other medium that is support off the shelf.
mario
QNX Master
 
Posts: 4132
Joined: Sun Sep 01, 2002 1:04 am

RE: multiple hosts connected via ethernet - still realtime?

Postby queBurro » Mon Jun 06, 2011 10:39 am

cheers for reply, that's been really helpful
I'm going to try qnet/ip and connect all hosts on my LAN via a router :) (and ditch the ethercat idea)
but... (I've been thinking about this) I should be able to use Qnet-native (i.e. not over IP) as well and connect all the hosts on my LAN with a switch/bridge since the ethernet frames at that level (OSI layer2) are routed on mac address? (I'm avoiding hubs and repeaters).
queBurro
Active Member
 
Posts: 79
Joined: Fri Jul 30, 2010 2:05 pm


Return to Realtime and Embedded

Who is online

Users browsing this forum: No registered users and 1 guest