PROFINET and ETHERNET, and what is VNC?

Thread Starter

abu1985

Joined Oct 18, 2015
73
I basically know only eNet IP and serial communication when it comes to automation, and I don't even know the real details, just how to commission the communication so I can get to programming. We have some SIEMENS HMI and PLCs from Germany and it's all PROFINET. Maintenance is telling me that they used to be able to connect to an HMI and have some ability to do a few things, and they used VNC Viewer to do so, but then one day couldn't connect anymore.

I take VNC Viewer (which I've never used before) and I enter the IP address of the HMI and it's supposed to connect. It feels like I'm missing something on my PC, but I'm told that's all they did. I can't get ahold of the builder of the equipment, they suck.

So all other details aside, should my laptop, using VNC Viewer, connect to a SIEMENS TP900 HMI that is PROFINET, without any other software or drivers?

I also cannot ping the HMI, and I'm plugged directly into it, but it's PROFINET!
 

kubeek

Joined Sep 20, 2005
5,718
As far as I know the device should have standard TCP/IP connection and IP address, along with the profinet connection. So I would start by checking what IP the HMI has.
 

Thread Starter

abu1985

Joined Oct 18, 2015
73
As far as I know the device should have standard TCP/IP connection and IP address, along with the profinet connection. So I would start by checking what IP the HMI has.
Yeah, you're right. The HMI has an IP address, so it must use TCP/IP connection. I will find out how to check the IP of the HMI.

Thanks
 

Yaakov

Joined Jan 27, 2019
1,612
If the HMI was using DHCP to get its address, it may have changed. If that happened, you'll need to figure out what address it has.

VNC viewer talks to a VNC server remotely and requires nothing more locally.
 

Yaakov

Joined Jan 27, 2019
1,612
You *could* use a direct connection to the device (make sure it or your computer are Auto MDI-X or use a crossover cable), then use a sniffer, such as the free Wireshark to watch the traffic which will include either DHCP requests, or packets with an IP address.
 

RobNevada

Joined Jul 29, 2019
54
First question is were you using a cross-connect cable to do you direct connect? Profinet is just half duplex ethernet. 4 wire instead of 8 wires. Most Lan connections are still half-duplex and only use 4 wires but the TIA standard is for 4 pairs or 8 conductors. If you don't have a cross connect cable you can also use a hub or switch. If you then use the Ping command and don't get a response you have a bad card either on your side or the target. To rule out your side ping another address and see if you get a response. Most likely it's the target.
 

Thread Starter

abu1985

Joined Oct 18, 2015
73
First question is were you using a cross-connect cable to do you direct connect? Profinet is just half duplex ethernet. 4 wire instead of 8 wires. Most Lan connections are still half-duplex and only use 4 wires but the TIA standard is for 4 pairs or 8 conductors. If you don't have a cross connect cable you can also use a hub or switch. If you then use the Ping command and don't get a response you have a bad card either on your side or the target. To rule out your side ping another address and see if you get a response. Most likely it's the target.
I was using a Cat5e patch cable, plugged directly into the HMI. I'm wondering if there used to be a switch and it got removed... So, using a switch over a cross cable, I can use my Cat5e from my laptop to the switch, and a cat5e to the HMI?
 

eetech00

Joined Jun 8, 2013
1,866
I was using a Cat5e patch cable, plugged directly into the HMI. I'm wondering if there used to be a switch and it got removed... So, using a switch over a cross cable, I can use my Cat5e from my laptop to the switch, and a cat5e to the HMI?
Hi

Let me start by stating...I'm not an HMI person but I am a network person :)
Most standard ethernet device interfaces are media dependent (but there are exceptions). That said, you should start with a small multiport switch and connect each device to it with "straight-thru" CAT5 or better cable. Once connected, if the HMI is an "embedded" type OS, the drivers should already be loaded and the link lights on the interface should become active...even without an IP. However, the PC link lights won't become active unless the OS network drivers are working. A PC to switch connection should be a "straight thru" cable and the link lights should become active when connected to the switch (if the PC network drivers are working). If the HMI lights (or switch lights) do not become active, the try replacing the cable between the HMI and switch with a crossover cable and see if that works (I doubt that this will work).

If the cable is a standard CAT5 or better cable (and it will be identified on the jacket of the cable), it will work with either half or full duplex mode. If the ethernet cable is not certified CAT5 or better, its functional capabilities become questionable, so don't use it.

BTW - You'll need to get the network communications working at this level (MAC layer) before any IP communications will work.

Hope that helps...

eT
 
Last edited:

Thread Starter

abu1985

Joined Oct 18, 2015
73
try replacing the cable between the HMI and switch with a crossover cable and see if that works (I doubt that this will work).
I agree. I believe crossover cables were used before my time. The auto MDI-X capability is probably on every networking device since 2010 or earlier.

I have a funny feeling the IP address for the HMI is not what was given to me in the email. I was originally thinking it had something to do with PROFINET or the VNC connection, but it doesn't look like it from all the help here.

Thanks for your time!
 

djsfantasi

Joined Apr 11, 2010
6,335
I agree. I believe crossover cables were used before my time. The auto MDI-X capability is probably on every networking device since 2010 or earlier.

I have a funny feeling the IP address for the HMI is not what was given to me in the email. I was originally thinking it had something to do with PROFINET or the VNC connection, but it doesn't look like it from all the help here.

Thanks for your time!
Not quite. Auto MDI-X wasn't invented until June 2011. Widespread adoption of the standard i don't think occurred until 2014 or later. So if either device in the network came before 2015, its possible if not likely that you’ll need a crossover cable. In the latter years, you would still need a crossover cable or a network interface card which supports MDI-X.
 

Yaakov

Joined Jan 27, 2019
1,612
Not quite. Auto MDI-X wasn't invented until June 2011. Widespread adoption of the standard i don't think occurred until 2014 or later. So if either device in the network came before 2015, its possible if not likely that you’ll need a crossover cable. In the latter years, you would still need a crossover cable or a network interface card which supports MDI-X.
I find a sniffer can save a lot of time thrashing about. In a case like this I wouldn't even bother with the GUI, just use shark from the command line and look for an IP address (or DHCP requests).
 

Thread Starter

abu1985

Joined Oct 18, 2015
73
Not quite. Auto MDI-X wasn't invented until June 2011. Widespread adoption of the standard i don't think occurred until 2014 or later. So if either device in the network came before 2015, its possible if not likely that you’ll need a crossover cable. In the latter years, you would still need a crossover cable or a network interface card which supports MDI-X.
This is all fairly new equipment, 2017ish. But I can make a crossover cable and try.

I remember my first engineering manager always talking about needing a crossover cable and I never needed one, so I blew him off about that because he always sucked when the comms portion of the projects. I started in 2014, and it might just be I caught the right time for that lack of experience.
 

Thread Starter

abu1985

Joined Oct 18, 2015
73
I find a sniffer can save a lot of time thrashing about. In a case like this I wouldn't even bother with the GUI, just use shark from the command line and look for an IP address (or DHCP requests).
Would I still need a crossover cable to use the sniffer?
 

Yaakov

Joined Jan 27, 2019
1,612
Would I still need a crossover cable to use the sniffer?
You will need whatever the proper cable is to make the link. If you get a link light (or traffic showing on the sniffer), the cabling is good.

At this point it would be very unlikely a laptop ethernet port would not be Auto MDI-X, but in any case, if you get a link indication (light or "network connected"), or the sniffer sees traffic, cabling is not the issue.
 

djsfantasi

Joined Apr 11, 2010
6,335
Reading the first post and doing a couple research searches on my own, I'm left with the impression that you can’t use IP to talk to a Profinet device. They are separate protocols at the media layer. You are trying to talk to a Profinet device with IP. Nope, I think it aint gonna work without a bridge between the two. Something is going to need to translate between IP snd Profinet.

Reference.
 

Yaakov

Joined Jan 27, 2019
1,612
Reading the first post and doing a couple research searches on my own, I'm left with the impression that you can’t use IP to talk to a Profinet device. They are separate protocols at the media layer. You are trying to talk to a Profinet device with IP. Nope, I think it aint gonna work without a bridge between the two. Something is going to need to translate between IP snd Profinet.

Reference.
From the Wikipedia entry for PROFINET:

Three protocol levels are defined:
  • TCP/IP for non time-critical data and the commissioning of a plant[2] with reaction times in the range of 100 ms
  • RT (Real-Time) protocol for PROFINET applications[2] with up to 10 ms cycle times
  • IRT (Isochronous Real-Time) for PROFINET applications in drive systems[2] with cycles times of less than 1 ms
The protocols can be recorded and displayed using an Ethernet analysis tool such as PROFINET Commander[4], PRONETA[5] or Wireshark.
 

djsfantasi

Joined Apr 11, 2010
6,335
From the Wikipedia entry for PROFINET:

Three protocol levels are defined:
  • TCP/IP for non time-critical data and the commissioning of a plant[2] with reaction times in the range of 100 ms
  • RT (Real-Time) protocol for PROFINET applications[2] with up to 10 ms cycle times
  • IRT (Isochronous Real-Time) for PROFINET applications in drive systems[2] with cycles times of less than 1 ms
The protocols can be recorded and displayed using an Ethernet analysis tool such as PROFINET Commander[4], PRONETA[5] or Wireshark.
Thanks! The reference that i found did NOT mention TCP/IP. And in fact explicitly compared Profinet and Ethernet/IP. Glad to have that clarified.
 
Last edited:

eetech00

Joined Jun 8, 2013
1,866
I find a sniffer can save a lot of time thrashing about. In a case like this I wouldn't even bother with the GUI, just use shark from the command line and look for an IP address (or DHCP requests).
Hello

A sniffer won't do any good if there is no MAC layer communications. The link lights will tell you if the MAC layer is working. However, if link lights do not exist at either end of the connection, then use a device that does have lights, like a small 4 port switch. You'll need a hub or manageable switch for a sniffer to be useful anyway.

eT
 

Yaakov

Joined Jan 27, 2019
1,612
Hello

A sniffer won't do any good if there is no MAC layer communications. The link lights will tell you if the MAC layer is working. However, if link lights do not exist at either end of the connection, then use a device that does have lights, like a small 4 port switch. You'll need a hub or manageable switch for a sniffer to be useful anyway.

eT
I said that.
 
Top