XBee
Another Baby Step
It has been a great weekend. The weather in Texas finally broke this morning (Labor Day 2011) as it was 68 degrees on my back porch this morning. The wind had been blowing hard all day before and the night before so I knew something was changing.
At 7:30 AM I sat on the porch in my “got dressed” shorts, sippin’ a cup of fresh ground French Roast coffee, munching on my last chocolate walnut brownie, and freezing my a** off! I’m not conditioned to under 70 when it’s been 105 to 115 for several months straight. Never the less, it was a great day to work in the shop.
The picture shows the BS2 micro computer in the foreground with an LED, a photo transistor, a piezo speaker (squeaker would describe it better) and a servo motor all hooked up to the I/O pins. That is the Propeller behind it also with some I/O stuff on board. Both systems are capable of communicating both directions on the wireless XBee network.
My theory has been proven to my satisfaction. Now I will begin to design the real world component application so I can test how those components will really work, then do radio range checks before I switch to the prototype boards.
It sure was nice to have a cool day in the shop.
The XBee Meets the Propeller
I got some time this Labor Day weekend (2011) to get an XBee interfaced with the Propeller processor. The pictures show the tiny interface board required to change the pin spacing from the XBee to fit the spacing on the Prototype Breadboard. This is some more of the micro soldering I have written about before. That’s all this board does is change the pin spacing.
What I can see here is the XBee running in full duplex. That means it can listen and talk at the same time. Just like talking on the telephone. Well, maybe I can’t do that but the telephone does it very well. 🙂 That’s a pretty big deal in the world of communication and has certainly removed some concern from me determining if this system will work fast enough for good control. I think that is not an issue at all now that I can use the Propeller.
Dedicating one of the cogs (processors) in the Propeller to just manage the communications means I can do whatever else necessary with the other cogs and not slow down the two way communications with the shore unit.
Hot Props
The Texas heat is killing me in the unconditioned shop. It is keeping me away from experimenting with the Xbee and the Parallax Propeller (computer). The inside temperature in the garage shop has been hovering at 100 degrees while the outdoor has been 105 to 107.
This is NOT for a few days mind you. We have been getting this temperature every single day for over two months steady. Yes, every day.
My new shop fan helps a lot at 80 or 90 degrees but near 100 or over it is just like sitting in a blowtorch. No fun. I tough it out in the morning (on weekends) for a few hours but by 10:00 or 11:00 AM, it’s breaking over 100 again.
Actually the little control computers don’t mind this kind of heat. They are very low powered so don’t generate much heat on their own. It depends on how much power you pull from them. I can’t say that about the PC computer that I use to write the application software. I believe it is maxed out with 105 degree ambient air temp trying to cool the processor, hard drive and other PC components. I had one of my CNC computers (another machine) shut down from the heat after running almost four hours. Luckily I had just finished the part I was cutting and was bringing the HB2 back to home position. I don’t do long CNC runs anymore in a hundred degree shop.
I like the newer Propeller processor. With 8 processors or “cogs” it is a “hot” multitasking little controller. That is figuratively hot. Not environmentally hot. I definitely have it earmarked to be the processor on the boat end. I was thinking about it today, and I am going to also use it on the shore terminal.
I don’t think I need its multi cog power on the shore unit but my thinking is to keep the software programming the same “flavor” for the entire project. I can put the BS2 STAMP to other uses.
I have a few ideas how to design the shore transceiver. It will be a small standalone unit. I was originally thinking of using a PC or Net Book as the shore terminal with just an XBee for the communication. The more I thought I decided a control box would be a better interface and not so expensive (to fix) when getting too close to the water, if you catch my drift. A BS2 would be plenty of computer smarts to run things but as I said above, I’m going to opt for another Propeller.
But hey! Who says I can’t play with my options.
With the Propellers at both ends of the communications I can dedicate one or more cogs in each Propeller to just run the XBees at their best transmission rates. Decision made.
If the Texas heat takes a few days off over the holiday weekend, I plan to get a lot more done with testing the com link. Then I can start designing the Propeller proto boards for the real link.
I also discovered there is a new Propeller multicore processor in the works. It will be bigger and hotter that the present Propeller. But hotter will also be the heat it generates. I suspect it will be more useful in applications where enough “shore” power is available and chip temps can be controlled. I think the Parallax Propeller has a great future and will be useful for a long time.
XBees Are Buzzing
They’re alive! I tell you they are alive!
I got two of the XBee’s talking to each other tonight. The usual things like “Hello World” and counting from 1 to 20. Not much you’re thinking but it is another milestone for me.
One of the XBee’s is directly attached to the USB port on my computer using that tiny little board on which I had to solder the two connectors. The other XBee is on the BS2 Basic Stamp development board. The BS2 computer is actually programed (by me) to talk through the XBee link to my main computer.
They were a few more feet apart but it is a beginning. I moved them closer together for the pictures.
You kiddo’s out there born with a blue tooth stuck in you ear are probably yawning about now, but I have to start somewhere. It will get a lot better and more detailed.
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!