LON
The Xbee Radio Communication Modules
Working with the network system for the Roboboat (RB) project is also a part of my amateur radio interest. It is actually microwave radio and it is one of the areas I have always wanted to explore. The frequency is located within one of the amateur microwave radio bands. It is shared with other services so it doesn’t need to be a ham radio project. Interestingly the frequency of operation (2.4 GHz) is very close the frequency (2.45 GHz) of most microwave ovens. I definitely don’t need to use my radio call sign to identify my cooking. The amateur radio band involved is 2390-2450 MHz. (2.390-2.450 GHz)
Note, at these power levels there is no danger of anything getting cooked.
I have never seen a requirement that amateurs must use ham radio frequencies. We just have to properly operate our radio under the FCC regulations. I am good with that and with a power of 1 milliwatt (0.001 Watts) and a range of a hundred feet, I can’t bother (or cook) too many folks. The “high power” version is 63 milliwatts (0.063 Watts).
Technically, as a ham I can do anything (sensible) I want with these radios on these frequencies. Of course I am going to do nothing but operate them. The only thing I might like to do (someday but not for the RB project) is experiment with feed horns and other antenna options to extend the range. That IS messing with the radio part.
The bottom line is I can claim to be operating an amateur radio station but in fact, these units do not need a license so anyone can operate them. There is no radio “tuning” involved.
The Xbee is far more than just a radio, it is a communication link. The radio communication is totally fixed. The interface the user must establish is talking to the module and reading the information from the module. How the data is handled (by microwave radio) between the modules is totally automated and beyond user control.
That means the method of talking to the module does NOT have to be the same at both ends. This simplifies the application of the product. Half the work is ready to go, no changes needed or are possible to the actual radio part. There are channels that can be selected and they need to be the same but that is setup and not radio tuning. Ain’t technology great!
Holy Micro Andy!
That’s what I was saying when I first examined the soldering work ahead of me. In the picture is the USB adapter board where I will have to mount one of the XBee modules. This is the one that will be the Base or shore terminal. All I have to do is solder those teeny tiny pins into those equally teeny tiny holes in the board.
Solder flowing across between any of those holes is not allowed. My normal soldering irons look like 10 penny nails up close to those little babies.
Time to break down and order one of those Weller WM -120 12 watt micro irons to do the job. There are some really fancy commercial micro soldering stations units available but they can cost more than these boards. The Weller is in the $40.00 range. Find one cheaper, get it!
It has a grounded cord unlike cheaper (Weller) models I have and the lower wattage is perfect for this size project. The super fine rosin core solder I already have. I figure there will be hundreds of these connections I’ll have to solder on this project. This is some of the smaller components these old eyes have had to work with. I love my magnifying headband.
The Fun Begins
I received the package from Parallax last night. It contains the XBee 802.15.4 Starter Kit. Sure is a small package of parts for the money. Ha, good things (hopefully) come in small packages.
This will provide the radio link between the boat and shore. Looks like a lot of options so I will be working on this communications link for some time.
I have a Basic Stamp computer to hook up to one of the transceivers and I will purchase a Propeller demo system very soon for the second transceiver. The third transceiver will be used for the master or base computer.
The Stamp computer will not be used in the actual RBB project but it will be a part of the learning process. Also a Stamp or another Propeller could become a part of the system later on.
Up Front, A Terminal Idea
Yesterday I got to thinking about what I need to do for the user computer interface on the shore side of the data link. A common terminal program and the debugger terminal (for the Parallax software) are all that is needed right now for the link communication testing.
For actual operation something more user friendly will be required for the “front end”. I am in the buildings controls business so this is not a great revelation. A control system is only as good as it looks and can be understood by the user.
I built serial terminal programs many years ago for the first MAC computer. I designed a text interface between the computer and the amateur radio teletype I was operating in my ham station (W5EHS). It was a two way text communications system. The software worked so well I had a fellow ham selling the programs for me. I had a lot of fun constantly adding features so I couldn’t freeze the design long enough to sell the program myself. Later on I made a few more changes and it worked very well as a packet radio front end.
So I am fairly certain I can do it again. Yesterday I loaded MS Visual Basic 2010 Express (a part of Visual Studio) and after a couple of hours punched out a fully operational (and professional looking) photo fetch and display program. Yes, it was a tutorial but it helped me realize my plan wasn’t out of reach. It looks like if I wanted to, doing the same in Visual C language would be no harder with the Visual Studio tools available. The Express versions of this software are free, so a no brainer to try.
I have considered a Linux based front end but most people don’t run around with Linux on their laptops. I have to work within something I can share with the most people. I think someday a cell phone could be the front end.
The shore side front end software may therefore be easier to build than the boat software. Total control reaction will have to be calculated in the boat software if there is any chance of autonomous operation. Some feedback into the shore display could be raw data and let the shore computer crunch it to display format. The shore side computer only has to talk and listen to the boat computer. A lazy job.
All these variable scenarios are a part of the decisions to be made. I am actually looking forward to the challenge. Having eight processors available in the boat computer has my mind spinning. I only have four in my home PC…
Why Parallax?
I have not chosen this controls manufacturer on a whim. There is a very huge variety of control microprocessor systems available, suitable for this project. In have no idea if this selection is technically the best product for the job. The truth is I don’t have the time or the money to test everything out there to make that kind of ultimate selection. I don’t think I need to.
I am not buying processors in lots of 1000 and will probably never. That means I need a low volume low cost proven product from a demonstrated successful manufacturer with lots of support for small volume users like myself. Here I am buying direct from the manufacture, not some high volume distributor who may consider me a pesky gnat because of my questions.
I have good experience with one of the Parallax products (the Basic Stamp) so first-hand I have knowledge their peripheral customer support systems and business philosophy. The company president (check his first name) Chip Gracey is a customer level, visual manager. He developed his product knowledge much the same as I did. That is with “hands on” pioneering from the very early years (late 70’s early 80’s) of the micro processor hobby development until the present. His start was back when Timex Sinclair’s and Apple II’s were still fresh off the tree.
Because of their comparably (with say Intel) low volume, their product has to be good to stay and grow in the business. Their market is the enthusiast both professional and hobbyist who want a small low power device with system boards and open I/O that can be totally customized to whatever need. Many times that can develop into OEM large orders, at least at the chip level.
That is all I need to make my initial selection. Check ‘em out for yourself!
Umm, sorry if this reads like a commercial. Just call it an endorsement. 🙂