Tonight I decided to put XBee to the test.  By the time we got Evelyn in bed, it was already pretty late.  My new RC transmitter also came in today, and I had to show it my neighbor.  After we discussed our various toys and projects, it was dark out. I recently procured an ultra light laptop for my wife, and this seemed like a good inaugural use for it.  After installing the XBee tools on it, and setting up another laptop on the front porch, I wandered down the street. My first trip was short.  Only to the end of the block.  After changing the default transmit\receive channel and turning the manners down (basically, I told the transmitter to transmit even if the channel did not appear to be clear) it was time for another trip down the block. So, on I walked.  When I got to the first stopping place, my signal was still great.  Half a block later, the signal was still quite strong...but it faded rapidly.  At the end of two blocks, I had just about maximized the range of the modules.  Not bad, though.  With...

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This evening, having just gotten my hands on another USB to TTL\serial adapter, there was but one logical thing to do...revisit my XBee experiments. My initial trial with XBee was mixed.  I got the devices working, but they were incredibly unreliable from only a few inches away.  That was shockingly short of the expected one mile range. This time I decided that measuring transmission distance in inches simply wouldn't do, upped the ante.  The following photograph shows the extreme communication distance that I attempted from my secret laboratory.  Please note that the modules are separated by feet! Sadly, my results were the same.  That's unfortunate, because I had blamed poor board design on my part for the failure.  Not so.  Transmission was slow, and characters dropped for no apparent reason.  The setup would be...

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One of the things I discovered while working with the XBee boards is that I need another reliable USB-TTL serial adapter.  Since the most recent incarnation of my USB board seems "Ok", I decided to print another one and use the chip that I rescued when I wrote about the Chip Quik. When I finished the board, it looked really good.  Almost perfect.  It had nice traces with very little stippling due to over-exposure.  I drilled the board, populated it, and plugged it in. My computer complained about an "unrecognizable USB device".  Great.  I checked the traces and found one short, which I fixed.  Still nothing.  I swapped out the passive components on the board.  Still no deals.  Next, I tried a different crystal (a through hole instead of surface mount).  Finally, I pulled the chip again and replaced it with a brand new one. It still didn't work.  My pretty board was now a mess.  ...

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Ever tried desoldering an SMD?  Did it work?  I tried once.  The heatgun that I used melted many of the plastic parts on the board, but I did get the chip replaced.  It was dangerous, and I wouldn't make a habit of such operations.  After working with my USB boards, I recently decided to try using some ChipQuik to pull the chip from a failed board.



ChipQuik is wild stuff.  It comes with flux and some alloy.  You use it by melting the alloy onto the pins.  When it mixes with the solder, it lowers the melting point of the solder-making it possible to heat all the pins and remove the chip without damaging the board.  This stuff could have saved me $100 recently, when I destroyed a stepper driver board trying to replace...

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Now that I seemed to have squared away some nagging problems with my USB development board, I was ready for a new and exciting challenge: wireless communication.  In case you have never heard of XBee, you really should hop over to www.digi.com and do some reading. After not nearly enough research, I decided to purchase a pair of XBee pro modules.  These little buggers are quite small, so they don't use standard headers.  This turned out to be a blessing in disguise because they also expect 3.3v for power, and communication.  The board I wanted to use to talk to the XBee module was powered by USB at 5V.  I knew that something would have to be done about the mismatch in voltage, so I did some digging about. A company called SelmaWare created the perfect board for interfacing with an XBee, at a reasonable price.  The AppBee-Sip cost me about $12 for two bare boards, shipped.  The parts required to populate the boards cost almost nothing from DigiKey.  After getting my modules and soldering the parts to the board, I powered one up and tried to talk to it....

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In June I wrote about some problems I ran into with a USB dev board.  The board seemed unusually sensitive.  When I would get my finger near a button, it would trigger.  Although it isn't thoroughly tested, the board below is my newest AT90USB development board.  It features a surface mount crystal (my first), and the ground outline around the board.  I also included pads for decoupling capacitors on the two buttons.

While I have not had time to completely test the board, it already seems to be less "twitchy".  While I would love to attribute this to my grounding changes, that probably isn't the case.  A friend informs me that RF coming from the processor probably is not terribly concerned with my silly ground.  At the same time, I did shorten some leads...and the longer, more problematic leads are right next to the grounded zone.

You might be asking a really good question right now. ...

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Digikey (of course).  Expensive, but enormous inventory and super fast shipping. Circuit Specialists.  Cheapest presensitized boards I've found yet.  About $2.50 each for 10 4"x6" boards.  Use the link.  It's an off brand, however I've had excellent luck with them.  Ocean State Electronics.  Saelig.  Simply bizarre inventory.  Good source for unusual components. JameCo.  The nice thing about JameCo is that they are usually pretty cheap, and they don't have a minimum order size.  Unfortunately, finding all the parts for a project at JameCo is nearly impossible. SparkFun.  SparkFun is cool because they carry odd stuff at reasonable prices.  This is one of the...

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When the first AT32UC3 parts became available on DigiKey, I immediately bought the only model that was available.  It was a 144 pin LQFP format, but I was confident that I could get the part working eventually as long as I could get it mounted on a prototype board.  As it turns out, (and as you will see in a moment) this was terribly shortsighted of me.

Unlike its more simplistic brethren, AT32UC3A requires three different voltage sources (5V from USB, 3.3V for IO, and 1.8V for core).  There are multiple inputs and grounds for each of the lower voltages.  Using jumper wires for these inputs, along with the clock signal results in (I am quite sure) the noisiest possible RF environment.  One that is hardly conducive to a working, high speed circuit.

There are a couple of other problems, such as plugging in the wrong voltage and damaging the chip.  The final problem I ran into is that in order to get all 144 traces into such a small area, I had to run very narrow traces.  That's well and good until...

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