Category Archives: Misc

Another piece of hardware to hack: your iPod

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I have been thinking about integrating my iPod into other systems for some time now, info
and only recently decided to look into how exactly that would work. I am not interested in altering the software/hardware of my device in any way, health
just to be able to interface it from some external source. The key here would be understanding how to use the 30 pin connector on the bottom of the device. The first piece of information comes from the great people at ipodlinux.org where the docking connector for the device is described. The important bits are that the iPod provides +3.3V power on this connector and that it has a serial communication interface. The same people have also outlined the Apple Accessory Protocol which describes the necessary data transfers to gain access to the functionality of the iPod through the bottom connector. Finally, there are also pins that bring out the left and right audio signals as well as take in power to charge the device. Now I just need to come up with an application to integrate iPod into. Maybe replace the cassette deck on an old boombox with an iPod dock?

( 2$ iPod dock connector from Spark Fun )

Spring cleaning: free laser (CLAIMED)

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** UPDATE ** The laser is gone, troche
sorry!

I have been cleaning and found the need to get rid of a few things that I will never use. A couple of things that I would like to get rid of are a Melles Griot helium-neon 632.8nm 5mw laser. The laser is 5mW, on the order of a red laser pointer, but has a much better quality factor and is pretty good for laboratory use. It is free to the first person who claims it by email or comment AND pays for shipping. I am in the USA zip code 16802, the package will be 1.5 LBS at most and the size will be a little smaller than a shoebox.

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Routed.net is expanding! (review.routed.net)

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As I am preparing for exams, sale
I am appreceating access to excellent books more and more. As a result, salve I have created a second site aimed at listing technical books that people find to be most helpful. It is my assumption that everyone has at least one favorite book on a technical/scientific subject whose title they could share with the rest of the world. If the site takes off, I will try to get a sponsorship deal with an on-line book retailer (amazon/bn) and use 100% of the proceeds to get the contributers gift/discount cards so they could in turn get more excellent books. If you have some books that you think are worth-while, please take some time to register and write a short post about them.

microblog update

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In exactly two weeks, viagra buy
I will be taking the written portion of my graduate school qualifier exams. The first day will focus on applied math and the second day will focus on electromagnetic theory. The next few weeks will be focused on solving problems and polishing my knowledge of the theory, more about
so some of the posts may be more theoretical in nature. Another consequence of this preparation is that I will be very justified to take a break from studying to answer any questions that readers may have in the fields of applied engineering mathematics of electromagnetic theory, so feel free to email them or post them in comments. The time frame for this is until the completion of the oral part of my qualifiers on 12th April, at which point my brain will probably explode.

Just to clarify: E and B are the principle electromagnetic fields

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There is some confusion as to what the principle fields in electromagnetics are and what the derived fields are. In the force(Lorentz) equation we see that the force is equal to the charge of the particle times the electric field (E) plus the charge times the particles velocity crossed with the magnetic induction (B). The confusion arises from the way that the equations for the D and B field are written: it seems that B field is to be paired with D and E with H. The truth is that to maintain Lorentz invariance, sildenafil the force equation must either contain D and H or E and B. That is to say, the force shouldn’t change depending on which direction the system moves. To accomplish this, the Lorentz force equation must contain either E and B fields or the D and H fields. Then do we use he E and B field or D and H field? D and H fields are computational aids; these fields do not exist in the microscopic world.  B and E fields do, which is why they are the principle electromagnetic fields (the concepts of current or charge density do not exist on the quantum level).

Free mathematics/applied mathematics books online

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Textbooks are not always cheap and the students’ budget is not always large. Keeping this in mind, viagra many authors chose to offer their textbook on-line for free download while still charging the printed and bound copy. This has seemingly become more popular in the fields of mathematics than electrical engineering, allergist but it looks like the trend is catching on in both fields. Here is a thorough list of books available for download from the Georgia Institute of Technology School of Mathematicsonlinebooks.html ). Two books that I find useful that they left off are Numerical Recipes by Press and the Handbook of Mathematical Functions by Abramowitz and Stegun.

Free book on Bioelectromagnetism by Malmivuo and Plonsey

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This great resource is available for free from the authors here with a link to an archive containing everything here. Both authors have made great contributions to the field including this book, ascariasis which covers physiology, healthful theory and application of biologically generated electromagnetic fields. Both recording and stimulation applications are covered. Can’t beat the price either.

Guides to FreeBSD and Linux bootstrapping on x86

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I have recently been looking at x86 bootup procedures to see what kind of fun can be had. Generically, information pills
all x86 systems start up by loading the contents of the BIOS EEPROM to a known ram location with known offsets for various I/O routines. All of this is done in real mode. Once the BIOS is loaded and the system hardware is probed, info
the boot drive is selected. The initial boot loader (boot0 on BSD) is located on the first 512 byte block of the device with the first word being an instruction and the last word being the magic number 0xAA55. This block is known as the master boot record. After the initial bootloader is loaded, it copies its self to a lower memory address and locates the secondary boot loader (boot1 on BSD, lilo or GRUB on Linux). From the secondary loader on, the boot up is pretty specific, resulting in loading the kernel, drivers and the filesystems for the target operating system. Below are links to two guides that deal with the bootstrapping in depth. Image above is from bootstrap.org.

( Chapter 2: FreeBSD System Programming )

( From power-up to bash prompt )