| Author |
Message |
wolf69
Joined: 20 Sep 2002
Posts: 117
Helped: 2
|
 31 Jul 2004 8:45 TCP/IP over RS-485? |
|
|
|
Hi All,
I was wondering if it is possible, or someone has done, to create a TCP/IP network over a 485 bus.
Bye!
|
|
| Back to top |
|
 |
goshka
Joined: 26 Jul 2003
Posts: 85
Helped: 2
Location: Tver,Russia
|
| 11 Aug 2004 17:37 TCP/IP over RS-485? |
|
|
|
It is possible. We do tftp connection qnx4 embedded system <-> Win hosh via rs-232.
This problem is solved by system configuration (running inetd on net.fd qnx driver)...
|
|
| Back to top |
|
|
goshka
Joined: 26 Jul 2003
Posts: 85
Helped: 2
Location: Tver,Russia
|
| 11 Aug 2004 17:42 TCP/IP over RS-485? |
|
|
|
free:
http://www.hwgroup.cz/products/hw_vsp/index_en.html
|
|
| Back to top |
|
|
wolf69
Joined: 20 Sep 2002
Posts: 117
Helped: 2
|
| 14 Aug 2004 10:21 TCP/IP over RS-485? |
|
|
|
Yes but with rs-485 is quite different: this is a bus, rs-232 is point to point.
From the practical point of view the difference is that in rs-485 there are possibilities of collisions, and you shouls manage 'hardware' addressed to identify devices... (but maybe they could be the IP)
Bye!
|
|
| Back to top |
|
|
Buddy
Joined: 13 Feb 2004
Posts: 34
|
| 17 Aug 2004 8:31 Re: TCP/IP over RS-485? |
|
|
|
Well, RS-485 is quite special. It is different to RS-232 only in noise emunity (has the ability to reamplify signals in nodal stations. The amplifications are done using opamps). Correct me if I'm wrong, RS232 protocol is pretty much the same as RS485.
Basically, I would take a look at the TCIP lean book for some ideas as it focusses on the protocol very much -> so you can learn how to modify it to suit the RS485. It's tricky but tell me if there is any success in it.
Thanks. By the way, the book I mentioned is available for download somewhere in edaboard (someone told me). 
|
|
| Back to top |
|
|
visioneer
Joined: 06 Jan 2002
Posts: 112
Helped: 1
|
| 18 Aug 2004 17:45 Re: TCP/IP over RS-485? |
|
|
|
If you are using RS-485 in point-to-point mode, U can use PPP or SLIP, it is a differential version of asynchronous communication as Buddy talked.
But If you are using RS-485 in multi-drop mode, U need a special arbitration or CDMA protocol in RS-485 network.
|
|
| Back to top |
|
|
feiutm9898
Joined: 31 May 2004
Posts: 224
Helped: 4
Location: Singapore
|
| 18 Aug 2004 21:33 Re: TCP/IP over RS-485? |
|
|
|
Hi, I want to ask about RS485.
Is that possible to use RS-485 TCP/IP connect to internet just like Local Area Network? Thereby, we can access one node at RS-485 TCP/IP network via internet or from other network which is connected together.
I need an answer and reason........ Thanks 
|
|
| Back to top |
|
|
davorin
Joined: 07 Jun 2003
Posts: 1490
Helped: 8
|
| 18 Aug 2004 22:11 Re: TCP/IP over RS-485? |
|
|
|
| feiutm9898 wrote: |
| Is that possible to use RS-485 TCP/IP connect to internet just like Local Area Network? |
What do you mean by this???
The Internet uses TCP/IP (besides UDP, ICMP and others ;o).
So no difference between talking to a local TCP/IP node or a node on the other side of the globe.
|
|
| Back to top |
|
|
wolf69
Joined: 20 Sep 2002
Posts: 117
Helped: 2
|
| 18 Aug 2004 22:11 TCP/IP over RS-485? |
|
|
|
feiutm9898: this is the same question I did.
Anyway, talking about linux, maybe there is a possibility to use ham-radio tcp-ip communucation package. A radio network is very very similar to rs485 mulipoint bus network.
Anyone has more infos?
Bye All!
|
|
| Back to top |
|
|
feiutm9898
Joined: 31 May 2004
Posts: 224
Helped: 4
Location: Singapore
|
| 18 Aug 2004 22:22 Re: TCP/IP over RS-485? |
|
|
|
| davorin wrote: |
| feiutm9898 wrote: |
| Is that possible to use RS-485 TCP/IP connect to internet just like Local Area Network? |
What do you mean by this???
The Internet uses TCP/IP (besides UDP, ICMP and others ;o).
So no difference between talking to a local TCP/IP node or a node on the other side of the globe. |
I mean RS485 is multidrop network, I don't know wheather each node at RS485 network have IP address (internet layer) that can be use for multi-network communication. Or RS485 just using the data link layer address??
Since if we lease a IP address from Internet Service provider, We can put our own network "online" or internet.
With RS485 network, possible.....???
|
|
| Back to top |
|
|
davorin
Joined: 07 Jun 2003
Posts: 1490
Helped: 8
|
| 18 Aug 2004 22:43 Re: TCP/IP over RS-485? |
|
|
|
| feiutm9898 wrote: |
| I mean RS485 is multidrop network, I don't know wheather each node at RS485 network have IP address (internet layer) that can be use for multi-network communication. Or RS485 just using the data link layer address?? |
Well..it was already mentioned above that your driver must take care about CDMA to avoid collisions...and for communicating with the Internet every node must have an IP address assigned..but those can be RFC1918 range like in most companies.
I've done a network driver for Linux where radio modem were used (also multiple accesses) connected via normal rs232 cable. And the simplest driver to build was to register the radio modem network as an ethernet interface (also CDMA).
The problem with SLIP/PPP is that they are meant to be used for point2point only communication. So you can't use it for nodes sharing same rs485 bus (o;
|
|
| Back to top |
|
|
goshka
Joined: 26 Jul 2003
Posts: 85
Helped: 2
Location: Tver,Russia
|
| 19 Aug 2004 14:01 TCP/IP over RS-485? |
|
|
|
Open TCP stack ...
http://www.embedded-electronics.nm.ru/ru/tcpip/tcpip.html
|
|
| Back to top |
|
|
wolf69
Joined: 20 Sep 2002
Posts: 117
Helped: 2
|
| 19 Aug 2004 17:20 TCP/IP over RS-485? |
|
|
|
davorin: that's very interesting. Could you share this driver? Probably if your driver works with radios it colud easily be adapted to rs485 envirorment.
Bye!
|
|
| Back to top |
|
|
