Newsletter Issue # 11

Real Time Automation's - Best Darn Newsletter 

IN THIS ISSUE
If You Don't Have Your Health...
Modbus - Why it Will Live Forever
Fun Facts and Trivia


STEAL OF THE MONTH...
Get a free RTA flying propeller toy this month only!

Email your name and address to: jladd@rta- automation.com by April 12th to claim your steal of the month.

SIDE BLOGS
3/7/13
Big and Little Indian
2/25/13
Simplicity
2/14/13
My Time at Kimberly-Clark
1/30/13
1734 Modules
1/16/13
ASCII to Something

 

YOUNG GUN AUTOMATION INSERT - Practical tips and information for young engineers.
 




If You Don't Have Your Health...


A Column of personal opinion by John Rinaldi, Founder and Owner of Real Time Automation.

My late father, Rocco Rinaldi, often said “if you don’t have your health you don’t have anything at all.”

Didn’t mean much to me as a punk kid but now that I’ve passed the halfway point to the century mark, being healthy and doing things to be healthy are more important to me than ever. As you get on in years you realize that you can’t do everything you did when you were 21.

I did my share of candle burning in my twenties. My first job was in what is now called IT at AT&T. I ended up with that job because I turned down the most perfect job in the entire world for a girl. Yup, I was 22 and in love. Her name was Mary and she was beautiful.

I had graduated with my BSEE and had an offer to work on the air defense systems at the NATO bases in Europe. I would be doing software installs at all the bases from Greece to Spain, Ireland, England and everything in between. EUROPE ON AN EXPENSE ACCOUNT. And I turned it all down for a pretty girl.

As what usually happens with young love, she left me. But by then, the NATO job was gone and I was managing mainframe data storage at one of the AT&T operating companies. Odd place. On my first day, I asked “How many people work here?” “Two percent” was the answer. As you might imagine, it wasn’t a hard place to excel, just put in a couple of hours a day of real work and you were an All Star.

But I did get to be on the company baseball team. Though they quickly figured out that I couldn’t catch a cold in right field, I did excel at the Irish Tavern post game. Closing it after most and following that up with a huge breakfast at the local 24 hour greasy spoon; George Webb's. I’d get home about 4am and still make it to work by 8. Today it would take me two weeks to recover from a night like that. At 22, I didn’t really understand how resilient my body was.

But now that I’m on the other side of 50 I want to enjoy life for quite a while yet. I want to see my grandchildren grow up, dive the Great Barrier Reef in Australia, do a dog sled trip in Alaska. There’s a bunch of drinks to drink and beads to throw in New Orleans. I still have to bicycle around Sicily and spend St. Pats day in Dublin. The list is long. I’m going to have to work hard on it so I’ve undertaken a study of what it will take to be the healthiest man alive.

Here’s what I’ve learned in no particular order:

· If you’re a man, look down at your waist. It might be painful, but do it anyway. Compare it to your waist at 21. The increase is directly related to your chance of a heart attack. No getting around it, you’ll have to eat less and move more. Yeah, I mean exercise.

· For some reason, flossing is really heart healthy. I can’t tell you exactly why, I’m still researching it, but there are strong connections between problems in the mouth and heart disease.

· There’s no perfect diet. Moderation is pretty much the key. Eat what you want, just less of it (a lot less if you look like your pregnant).

· Only eat foods that will spoil (no Hostess HoHos but I guess we don’t have to worry about them anymore).

· Stay away from the white stuff (no, not talking about cocaine though you should avoid that too). I’m talking about things like pasta, rice, baked potatoes. I grew up on pasta. We ate pasta two, three or four times a week at my house. Not sure I can do this.

· Stay away from Lasik. All I know is that the inventor of Lasik wears glasses and doesn’t want to get Lasik.

There are lots of arguments about all this stuff, of course. First there’s the Jim Fixx argument. Eat healthy small meals. Exercise every day for hours and hours – and then drop dead young like Jim Fixx did. Then there’s the caveman approach. Take your shirt off, take your shoes and socks off and run through the woods lifting logs and toting rocks here and there and all that. I think you guys with long beards get a membership discount.

In the end, I’ve decided to get at least 30 minutes of exercise on 3 out of every 5 days and use a personal trainer to avoid losing muscle mass. I’m going to be trying to lessen my calorie intake and take in most of those calories before 3pm.

I’ve got 25 pounds to lose. I’ll let you know how I’m doing. If you’ve had some success with this or advice you’d like to offer I’d like to hear from you.

 
Trivia Challenge

· True or False: At the age of 16, St. Patrick was kidnapped, enslaved, and sent   to Ireland to work tending sheep.

· What does the Irish phrase "Erin go Bragh" translate to?

· What day did St. Patrick die?

· What profession are Leprechauns often associated with?

· According to myth, it is said that St. Patrick drove what animal out of Ireland?

 

Answers located on bottom of page.


Modbus - Why it Will Live Forever

There’s an old joke that everyone wants to go to Heaven but no one wants to die. It’s also true that there is one sure fire way to avoid all the pains and suffering of old age – die young. I think I’ll pass on that.

I got to thinking about this today as I looked through some of the emails we get from customers. It seems that the majority of them want some form of Modbus connected to devices on all sorts of other networks. Why is that? Well Modbus has a lot of advantages:

1. It’s small – you can easily fit it into the smallest of processors. No big RAM or ROM requirements.

2. It’s cheap – you can build it yourself or you can buy it for a very small charge.

3. It works with all processors – anything that has a UART can run Modbus.

4. It’s simple to deploy – it’s just daisy chained RS485. Wire from one device to the next to the next.

5. Very simple data typing, memory map and operating functions – it’s simple enough that most competent programmers can implement it within a week or so.

6. There’s a lot of it out there – you can’t go wrong with a Modbus interface. Everybody understands it and can usually find a way to move the data where it needs to go.

When you think about this, it’s really true, MODBUS WILL LIVE FOREVER. A big reason for that is the guys that build devices are not network communication experts. They are domain experts in pumps, chillers or drives or whatever. They need a way to talk to their device. Something simple, that isn’t going to cost too much and that they can get implemented quickly. The answer for the last 30 years has been Modbus and I see no reason for it to change now.

Let’s review this protocol that will live forever and take a look at both Modbus RTU and Modbus TCP.

Modbus is considered an application layer messaging protocol, providing Master/Slave communication between devices connected together through buses or networks. Modbus is intended to be a request/reply protocol and delivers services specified by function codes. The function codes of Modbus are elements of Modbus’s request/reply PDUs (Protocol Data Unit).

In order to build the Modbus application data unit, the Client (or Master) must initiate a Modbus transaction - the function that informs the Server (or Slave) of which action to perform. The format of a request initiated by a Client is established by the Modbus application protocol. The function code field is coded into one byte. Only codes between 1 and 255 are considered valid, with 128-255 being reserved for exception responses. When the Client sends a message to the Server, the function code field informs the Server what type of action to perform.

To define multiple actions, some functions have sub-function codes added to them. For instance, the Client is able to read the ON/OFF states of a group of discreet outputs or inputs. It can also read or write the data contents of a group of Modbus registers. When the Client receives the Server response, the Server uses the function code field to indicate either an error-free response or an exception response. The Server echoes the request of the initial function code in the case of a normal response.

Modbus packets are only intended to send data; they do not have the capability to send parameters such as point name, resolution, units, etc. If the ability to send such parameters is needed, one should investigate BACnet, EtherNet/IP, or other modern protocols.

Despite the limitations of Modbus RTU, there are still many good reasons it is still a contender among other industrial automation protocols. For one, Modbus RTU is much easier to implement than newer protocols, and it is a dominant force in the market place. Modbus RTU also requires significantly less memory than most other solutions. To implement Modbus RTU, you can fit the necessary 2Kb on a small 8-bit CPU or PIC processor, whereas with BACnet and EtherNet/IP, you may require 30-100Kb of memory.

Standard Modbus RTU node addresses are 1 to 254, with 0 being reserved for broadcast messages and write only. However, the 0 address is rarely used due to the fact that there is no confirmation that the message was properly received at the Server node. This doesn’t have much affect if your physical layer is RS-232 as only one node can be implemented anyway. RS-485 limits the number of nodes to 32, though some drivers will allow you to extend the amount.

There are two basic data types in Modbus; Modbus Coils and Modbus Registers. Coils are bits – either input status bits or output control bits. Registers are 16-bit unsigned data items. That’s it, just two data types. Modbus has the simplest data scheme of any widely used communication protocol.

The Ethernet version of Modbus is Modbus TCP/IP. A Modbus packet in Modbus TCP/IP is nearly identical to a Modbus RTU Packet. The only difference is that the CRC (cyclic redundancy check) is not used with the Modbus packets in the Modbus TCP message.

 
 

Fun Facts

·There are over 30 million U.S. residents who claim Irish ancestry. That's about nine times the population of Ireland itself.

·The Irish flag is green, white and orange. The green symbolizes the people of the south, and orange, the people of the north. White represents the peace that brings them together as a nation.

·St Patrick was born Maewyn Succat; he took the name Patrick when he became a priest.

·On any given day 5.5 million pints of Guinness, the famous Irish stout brand, are consumed around the world, but on St. Patrick's Day, that number more than doubles to 13 million pints.

 

 
  Trivia Answers: True; "Ireland Forever"; March 17th; Shoemaker; Snakes
   
  RTA Website