I’ve been using the XBee and the XBee Pro over the last couple of weeks and I’d thought I would share my notes on them:

1. The maximum “recommended” baud rate is 115200 baud.  The specifications says that the max baud rate is 250000, but that is for RF transmission. You can set nonstandard baud rates and even go higher than 115200 using the API or AT commands, but it could lead to corrupt data and lost packets.

2. Hardware “Flow Control” is a MUST. Always check the CTS (Cear to Send) line to see if the XBee is even ready to send a new packet. If you don’t, the Xbee’s send buffer will fill up quickly and packets will be lost.

3. You can actually use two different baud rates on both sides. Lets say you have a device (such as a USART camera) that communicates at 9600 baud. You can configure the Xbee to run at 9600bps , and send it to another Xbee that is configured to say 38400 baud. Sending to a device with a higher baud rate is usually not a problem, but sending to a lower baud rate device can lead to packet loss if you don’t use flow control.

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I’m in a writing mood, so I’d thought I would share my thoughts on how I started to become fascinated with electronics and include some helpful advice to beginners.

I’m a code monkey. I liked to program because everything I produced was (virtually) free. I programmed maybe 20% of the time I was at a computer for the past 7 years. It started to get kind of old, but the thought of creating and hacking at things still lived in me. I wanted to build something physical that can interact with other people. I knew I had to learn electronics, but I didn’t have the time or the idea on where to start.

1) My first bit of advice is College. I’m currently attending Tennessee Tech University as a Junior in Computer Engineering. The biggest point of college is to start you off with a career. You will end up learning at least 70% of all field-related knowledge while in the work force. If you don’t believe me, go up to a graduated engineer and just ask. It’s true. So, go to college but only use it as a crutch.

2) Can’t go to college? Well, experiment! Play with electronics, study how each component works, and make sparks!* The best way to learn something is by doing it. A little side story.. during Circuits I, I played with capacitors. They are basically “temporary” batteries that can store charge and release it virtually at once. This made sparks, even at low voltages. I had a lot of fun with those things, and a whole new respect for higher voltages (ouch!)

* Be reasonable, don’t get hurt. Don’t sue me for something stupid you did without research.

3) Make something! I suggest starting with an Arduino. These things are very basic microcomputers that you can program with any PC. What is great is that these things are the real deal. You can prototype plenty of electronics gadgets with them and the community is HUGE. If you ever have a specific problem there is a great chance someone already posted a solution on the internet. On top of all of this, an Arduino costs only about $30. From the same retailer (Adafruit Industries), you can also get an awesome experimentation kit for $85.

So, to continue with my obsession with lighting, I wanted to design my own high brightness wall washer. It had to be overkill though, that’s just how I roll! My project is named the “Blinder,” for obvious reasons. One unit has 8 high brightness 3W multicolor LED’s mounted to a long aluminum backplating. The system pulls approximately 8.4 amps at 5V (42 watts) during full brightness. Since I am cheap, I’m using a 300w ATX power supply I ripped from an old computer. I can control the unit wirelessly using Xbee which talks to an AVR microcontroller which controls the LEDs via an LED Driver (Texas Instrument’s TLC5947). All of these components are mounted onto a custom-designed PCB I had manufactured at Gold Phoneix PCB. To top all of the insanity, I’m making 3 of these! Yea, you’re right.. I just cranked it to 11.

The build is currently a work in progress. I have only started to finish one of them. Since it is final’s week, I haven’t had much time to work on them. I will post the full source code, schematics, and videos sometime after Christmas break. Until then, enjoy the timelapse footage of me building the LED drivers one at a time with a short video of one set running the demo software.

So far I would like to thank TNTech’s Baja Team (specifically Frank Smith) for letting me use their shop and helping me with the metal forming. Mwhaha

Edit: I found a bug in my firmware used in testing that reduces the brightness by a half (I needed one more bit shift!) – so the video at the end of the timelapse doesn’t do much justice anymore!