Personal Area Networks Part 5 of 7

Personal-Areal-Networks-part-5The previous article in this series discussed the characteristics of the physical part of the radio including the frequencies, data rates, power and bandwidth of the radio. Now we are going to address the organization of the information on the “wire” or air in this case.

 

This part of 802.15.4, and really any other networking technology, is termed Media Access and the low level software that implements the Media Access is called the MAC or Media Access Controller. A MAC is responsible for both organizing the data received from the application into low level data frames, synchronizing access to the medium, checking for errors and a myriad of other things.

 

One of the tasks of an 802.15.4 MAC is to present the device to the network as one of the two types of devices defined by the 15.4 specification; a Full function Device (FFD) or a Reduced Function Device (RFD).

 

Reduced Function Nodes have very limited capabilities. RFDs are single purpose end device nodes like a temperature sensor or a light switch. These devices are often battery powered as they need only communicate intermittently. Reduced function Nodes can only communicate with a single Full function Nodes (FFD). FFD nodes can have device capabilities like RFDs but unlike RFDs they can extend the network by serving as network coordinators.

 

One way nodes can be organized is a Peer Network as shown in Figure 1. Any FFD can communicate with any other node in range. Each RFD associates with one and only one FFD. The PAN coordinator provides the interface and structure for the entire network.

 

 

Figure 1 – 802.15.4 Network Organized as Peer Network with Coordinators

 

A network containing only FFDs is a true peer network with the capability for any FFD to communicate with any other FFD in range. Figure 2 illustrates an FFD network composed of Full Function Devices.

 

Figure 2 – 802.15.4 Peer Network with all Full Function Devices

 

There are two types of network coordinators; coordinators and PAN coordinators. Both are FFDs. Coordinators are FFDs that provide links or associations to other FFDs and RFDs. There can be multiple coordinator devices in a PAN but only one PAN coordinator. The PAN coordinator (Red Node in the diagrams) is the “owner” of the PAN and provides the PAN ID that uniquely identifies the network to the outside world.

 

The 15.4 standard does not define how the PAN ID is selected. Any FFD can decide to chose a PAN ID and become a PAN Coordinator. Other FFDs and RFDs can then associate with it and “grow” a wireless network. [If that sounds somewhat haphazard you need to remember that we are discussing the very lowest level software layer here. There are other higher layers that provide much more structure.]

 

A PAN coordinator and most FFDs are typically powered nodes while RFDs are often battery powered. The PAN coordinator will usually have access to a wired network and be …

Allen-Bradley PLC to Profinet

ControlLogix-to-Profinet
Many of you know that I have been educated as an Engineer. I
did the whole thing. Went to Engineering school, got a BSEE and graduated Cum
Laude.

 

If you look up Cum Laude on Google (nobody uses the
dictionary anymore) it is a Latin term for “he spent too much time in the library
instead of at the Gym Bar chatting up the young ladies from O’Donnell Hall”.
Yeah, I was the guy in the library every night practicing calculus problems. I
got a full 8 hours sleep almost every night. Still fell asleep in Chemistry
class but that wasn’t the lack of sleep.

 

So, I’m an Engineer, a software Engineer. And I’ve done some
really fine work. None really at RTA lately, I have people for that, but at
Kimberly-Clark and Allen-Bradley. I Got a lot of recognition there for my
software expertise.

 

But what I am going to tell you about today is really
amazing to me. It’s beyond anything I had hoped for. We releasing a product for
moving data from ControlLogix PLCs to Profinet IO Controllers that just amazes
me. They’ve done an incredible job making something that is so functional and
so adaptable and so easy to use that I think this will be a real hit.

 

The product is our 464ETCPS. On the PLC side you will be able
to read and write any Tag in a ControlLogix or CompactLogix PLC. Or write any
file in a PLC5E, SLC5/05 or MicroLogix. That’s pretty cool.

 

The real interesting thing is what you can do on the
Profinet IO side. If you’ve been paying attention to me you know that all
Profinet IO Server devices look like I/O racks. They have a series of Slots for
Input and Output. In the real world, each slot is populated with a specific
type of module; 16 channel discrete input or maybe, 4 Channel Analog. Well,
that kind of organization follows here.

 

You configure the Profinet IO side by assigning data types
and data lengths to each of the 10 input slots and 10 output slots. So input
Slot 1 may be 4 items of Floating point data. Input Slot 2 may be 16 items of
Discrete input bits. And you do the same for each Output Slot.

 

Here’s the magic. You can then either manually assign all
your Tags (or files) from the Allen-Bradley side to the slots on the Profinet
IO Server side or let our Automatic mapping tool do it for you. If you have 10
Floating point tags they will end up in the first slot configured for Floating
point with unassigned Floating point items. When that slot fills, any remaining
floating point tags are assigned to the next slot configured for Floating
point.

 

All of this is done easily and automatically for you. It’s
very IMPRESSIVE. If you need to move Tags from ControlLogix to a Profinet IO
Controller, the 460ETCPS is going to …

MY CRYSTAL BALL IS HAS SOME SPAGHETTI SAUCE ON IT BUT IT STILL WORKS

Speghetti-On-My-Crystal-BallI’m in the great city of Bologna today. This is probably my favorite city in Italia. That’s probably shocking to people that have visited
Italy. Bologna not Rome? Not Florence? Not Venice? Have I lost my mind?

There’s very good reasons to like Bologna. For one, there’s
not a lot of Americans here. It’s not one of “THE” destinations in Italy. In
Rome, it’s hard to hear a language other than English especially in the summer
time. Secondly, the food is absolutely awesome. Bologna is in the plane of the
PO river, a great area for agriculture. Everything is fresh. And all delicious.
You can get Tagliatelle, Tortellini, Pasatelli and more. The only thing it’s
missing is the ocean. I’m as far away from water here as you can get in Italy.

One of reasons for me to come to Italy this week is to
attend the OPC UA Day – Italia. About 40 Italian companies showed up yesterday
to learn what UA is and how they can use it. Italy is a huge center for machine
builders and just like everyone else, they are under pressure to move data from
their machines to MES systems and other places. Claudio Fiorni, the R&D
Manager for Progea, is working hard to advance UA technology in Italy among these
machine builders.

The organizers did a good job detailing all the benefits of
UA including platform independence, scalability, security, a very advanced
mechanism for building data models and a lot more. They also announced a few
things I had never heard about, one of them being the capability to support
File Transfers. This new service is identical to FTP but doesn’t require you to
open an additional TCP port in the firewall.
Plus UA now will support HTTPS and you will be able to use that security
layer instead of the one embedded in UA. Very cool enhancements.

Another interesting piece of information was more details on
all the different protocols that are going to drop their transport mechanisms
to use the OPC UA transport mechanism. Working groups in a number of different
industries have examined the UA standards and have realized that they can keep
their current object model and use the more secure, more reliable, more
flexible transport layers that UA provides. Efforts are being made all over the
world to encode these proven data models in the UA format. I am not surprised
to see the great momentum for this and that it continues to grow.

My takeaways from all this? Here’s what I think:

CONTROL PROTOCOLS
– Protocols like Profinet IO,
EtherNet/IP and Modbus TCP will continue as
they are now. These are still the very best mechanisms from moving I/O data
from sensors into controllers. I don’t think any of that will change. RTA
products for moving data from
EtherNet/IP, Profinet IO and Modbus TCP
to controllers will continue to be
needed in many different industries.

SPECIALIZED PROTOCOLS
– Things like BACnet for Building Automation, 61850 for …

ASCII Part 2

ASCII-Part-2-May-6-2014Last night Elon Musk was on 60 Minutes. Now, generally I don’t watch much of 60 minutes anymore. It was really hot about 20 or 25 years ago. Everybody had to see 60 minutes but now, like everything else, there are so many more ways to get news that it is kind of irrelevant.

So Elon was on and they went into depth on his Space X adventures and what he’s done with the Tesla. Very cool stuff. I came away really liking the guy. I like that he came from humble roots with tenacity and vision and really made something of himself.

The Tesla is a pretty unique car. It’s all electric. No other backup power system. When the batteries die it’s a boat anchor just like a gas powered automobile is. There’s a 17 inch touch screen control panel. And some kind of odd, gull -wing doors. Some of the things solve problems but others, like the doors, are just showy.

This made me think of our ASCII products. We really try to focus on the former not the latter. Our products solve real problems. We don’t do things for show.

Take how we can assemble or disassemble strings from individual data items. Our devices for example, can get an ASCII string from an ASCII device, disassemble the component ASCII characters, convert them into Floats, Ints and other data types and then transfer them to some other device, like a Modbus PLC. And we can do the same in reverse. We can take data from a group of tags in a ControlLogix PLC, convert those tags to ASCII strings and then send the string out with some appropriate delimiters like commas, spaces or tabs. Checkout that link to see how easy it is to assemble and disassemble ASCII strings from ControlLogix Tags.

This works exceptionally well with our TCP transports. There are a lot of devices now that have Ethernet but don’t use a protocol. It’s just transfers raw data over Ethernet.

With our latest software enhancements you can get data from EtherNet/IP devices, Modbus devices, BACnet/IP devices and others. You can then send that data to a TCP device as a delimited ASCII string. You could also send it out to some ASCII RS485, RS232 or USB device.

Of course, you can also do the reverse. Pull ASCII data in from USB, TCP, RS485 or RS232, disassemble it, convert it to ints, floats or whatever you want and send it to devices over EtherNet/IP, DeviceNet, Modbus, Profinet IO or any of the other networks we support.

That’s a pretty cool feature and it serves our target market perfectly. It solves a problem that a lot of our customers have without being showy.

No, we don’t have any gull-wing doors on the side. But it is all Electric!

Think I can get on 60 minutes???

John…

Can I Admit Something

Can-I-Admit-Something 

Can I admit something? I am just not an e-reader kind of guy. I really like sitting there with a book on my lap, turning pages, writing words I don’t know inside the back cover and highlighting stuff that I’d like to come back to.

 

I also like having an overflowing bookshelf that I can look through once in a while. I see a book I’ve read, flip through the pages and see what I highlighted back then. Some, usually wealthy people, call a bookshelf like that a “Success Library”. I don’t know about that but I do know that I like looking at it every day.

 

There are a number of other old, obsolete things I just like. For example, I like my Garmin. It’s not that I hate the mapping system on my iPhone; it’s that the Garmin is more functional and has a better user interface. I can get by using the iPhone for directions but I just miss the ease-of-use I have with the Garmin. I think it’s a shame that they’ve lost a huge portion of their sales to the mapping apps on phones.

 

I also like old-fashioned DVDs. Netflix is OK but again that user interface is really awful. With my DVDs, I don’t need to wonder if there is enough bandwidth in my neighborhood to watch my movie. And I can see trailers, I can easily turn on captions and I get audio commentaries. And they’re right there for me when I need them even though I do realize that I’ll probably throw them all out when the next wave of movie players hits the market.

 

Where am I going with all this? I am working up to saying that I really like DeviceNet and Profibus DP. I know it’s not politically correct in today’s day and age but I really like those old technologies. It’s kind of like THAT awkward time in a relationship. You’re afraid to say “I Love You” in case the other person responds with “ah….ah….. thank you”.

 

In this day and age we’re all supposed to be in love with everything Ethernet. Revel in DHCP, DNS Servers, routers, switches, MACs and PHYs. I think that’s what Dorothy said on the yellow brick road: “Routers and Switches and Macs and Phys Oh My… Routers and Switches and Macs and Phys Oh My”.

 

It’s not that I don’t appreciate the simplicity of Modbus TCP. It’s not that I don’t admire how easy it is to make an EtherNet/IP Source Code stack operational and it’s not that I don’t marvel at all the features in a Profinet IO Source Code stack. I just like the old time, bare bones, working man style of Profibus and DeviceNet.

 

Profibus has balls. It has to. Anything that can operate that fast and force device vendors to include ASICs and special software stacks in there device has to. DeviceNet, on the other hand, is …