μblog: engineering from the trenches

Today’s entry, NXP’s PCF8584 I2C bus controller, is again courtesy of Neil B. Thanks again!

pcf8584-10x-stitch.jpg

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“…hello, is this tech support?”

Unknown to myself until today, it appears that the United States Bureau of Reclamation operates many of the nations hydroelectric power plants. As such, they also make available the Facilities Instructions Standards and Techniques (FIST!) manuals which are a wealth of interesting information. While I was initially looking around to find some good information on synchronizing dynamo generators, I think that their Abnormal Operations Generic Technical Guidelines for Power Stations manual is quickly becoming my favorite. The most interesting part starts with section 4.0 (p. 12) where the bureau outlines generic, step by step, guidelines for responding to various abnormalities in the plants operation. Although the contents are fairly straightforward and the messages clear, the name of the document is quite formidable. Be sure to check out the rest of the FIST manuals if you like this sort of information.

( vol1-12.pdf )

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I have recently sent my Q to greener pastures in favor of a Samsung SCH-i760 (Verizon). I have yet to experience the phone at great lengths, however, I have a few things to share with prospective users:

• This phone has a touch-screen and runs the full PocketPC version of Windows Mobile 6 (as compared to the smartphone edition on the Q)
• With the extended battery (1500mA), the phone is thick (see below) and almost twice as heavy (6oz) as Q
• That’s okay because it hides a full QWERTY keyboard
• The extended battery stays charged for 2-3 days with moderate use (AIM, constant email checking, few phone calls)
• There are a lot of buttons (all around the edges of the phone)
• No Verizon Get It Now
• Can be used as a broadband modem without paying the $15 service fee
• Has a better camera than Q (both are 1.3MP)
• Google maps can be moved using touch screen
• Built in 802.11b/g, bluetooth, stylus for screen
• Did I mention the phone is heavy and bulky?
• Fairly intuitive usage and notifications
• Back-lit keyboard
• LED that can light up half of the bedroom while being charged
• Same Thunderbird integration (via BirdieSync)
• Non-standard connector (as compared to Q’s mini-USB)
• Cannot be charged with included non-standard to USB cable
• MicroSD slot, just like Q
• Supports Adobe flash and various flash video sites

All in all, I am happy with the i760 so far, more so than I was with the Q. Throughout the benefits, the main downside of the phone is its thickness which makes it fit less well in the front pants pocket. The interface is more polished, however, there is a small delay when the phone is switched between landscape and portrait modes while sliding out the keyboard. I will try to post small hacks as I see them come up, however, you will have to look for the modem bit on your own. Please feel free to ask any questions if you are considering one and are not sure or have some difficulties.

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This week, we have a 3-wire EEPROM from Atmel, the 93C46. It is interesting to note the amount of real-estate dedicated to the memory as compared to the supporting circuitry to drive the writes and run the three-wire protocol. Thanks again Neil for this submission.

at93c46-20x-stitch.jpg

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In my battle with transfer function estimation, I have been dealing with many noise problems lately and have come across this application note from TI regarding the calculation of noise figures for basic op-amp circuits.  This noise figure deals with the ratio of circuit signal-to-noise ratio (SNR) at the input versus the output. The article goes through the derivation of noise analysis equations due to thermal noise in resistive elements and due to rms noise figures of the active device and goes on to quantify the noise figure as a function of temperature, resistances and op-amp parameters. This can be useful in determining performance properties of circuits given a set of passive components and can be used to define a “best case scenario”.

This all well and good, but then one might ask what noise has to do with system identification (transfer function estimation)? The simple answer is that the frequency-domain transfer function can be determined by passing “noise” through a system and comparing the spectral properties of the output versus the input. The idea is that white noise has a flat spectra (over infinite time) so the transfer function can be accurately determined for all frequencies (again, given infinite time). If infinity is too long a time to wait, one trick is using something called periodic random noise to give a well defined spectral distribution in finite time. A Gaussian random number generator can create white noise, however, an inverse Fourier transform is used to to generate the periodic noise.

Essentially, enough sinusoids are added together to cover the frequency range of interest with equal amplitudes and randomized phases that are distributed over +/- pi. The amplitude will relate to the desired resulting rms value for the noise and the number of summed sinusoids. The frequencies of choice should line up with the sampled frequencies in the following FFT that will be computed to compare the spectra of the input and output signals. The signal will now look like noise and will be “random”, however, all of the frequency domain components will maintain their amplitude and phase through the whole procedure leading to less variance in the FFTs.

( slyt094.pdf )

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I was not too surprised when I read about BestBuy’s new official trade-in program (on Ars Technica). I figured that they were following GameStop’s lead and getting into the business of reselling used hardware. Curiosity lead me to put in my broken Dreamcast console, just for entertainment. Again, I was not surprised to learn that the broken console without any accessories or games did not have any trade-in value. What did surprise me was the option to recycle the console via BestBuy’s service at no cost to the consumer. Most of the time, it would be easiest for everyone to just find a local recycling center and simply drop off the hardware, however, sometimes there are no convenient locations. The next easiest recycling method would be filling out the form via the BestBuy service, boxing the device(s) and putting on the shipping label. The current weight limit for processing is 70lbs, however, this is definitely a step in the right direction, especially for a company that sells so many electronics. I hope that the inclusion of the recycling option was not a fluke and is continued to be honored by BestBuy. All I can say at this point is job well done.

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This week we are presented with the MAX274 from Maxim (thanks again Neil!). This is an older low-pass filter IC and it should be noted that it requires substantial external components. The on-chip capacitor design is an interesting island pattern, it is possible that the inductances of the traces that link up the squares are also integrated into optimizing the design.

A quick reminder about the file naming scheme: the 10x means that the 10x magnification objective was used in addition to another 10x magnification in the optics. This means that a file name with 10x in the name is actually 100x and 20x is 200x. I know it might be slightly confusing, however, I don’t know if I should change at this point given that I used this poorly designed naming convention for all previous posts.

max274-10x-stitch.jpg

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I randomly found this book in the in the sciences section of a local book store and decided to buy it given that it was only about ten dollars. I was pleasantly surprised with the depth of the book, the readability, and the commentary of the author on applying the latest understanding of our physical world to the long-standing philosophical questions such as those dealing with determination and free will.

The book starts out by giving a summary statement of physical and philosophical advancements to year of the first publication (1943). For me, the historical accounts of philosophical advancement was very interesting given my ignorance of the subject. I was surprised to learn that Gottfried Leibniz, one of the fathers of calculus, had also tried to create a operational logic system to make philosophy universal and on par with mathematical proofs. Unfortunately he failed and to this day this universal language is still missing. The physical overview spends substantial time on new discoveries in quantum mechanics and goes over the probabilistic nature of the universe and ties this together with philosophical understanding of reality, knowledge and will. I will not spoil the conclusions, however, I will mention that they are well stated and supported.

Besides the substantial new (to me) content of this book, I found the book to be easily readable and understandable. The book was very complete and even offered references for further study of various intricate subjects. The organization of the book superb where each chapter built on information from the previous chapters and everything flowed together. I highly recommend it does a good job of provoking critical thought and introducing the reader to questions regarding our position and some of the motivations for the way we carry out our lives.

ISBN 0-484-24117-3 (This is the ISBN number off the back of the book, however, I noticed that this book is a little hard to find. A title and author search might work better than the ISBN.)

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Today we are looking at the PIC16C63. This is an entry level, one-time-programmed, device from the 16 series and having fairly standard features. This is also a reader-submitted chip, the first of seven, so the next few IC Fridays are all thanks to Neil B.

pic16c63-10x-stitch.jpg

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As some of you may have known, I am a bit of a FreeBSD enthusiast and have been using it regularly since around the time of the Linux fragmentation/teardrop vulnerability. I have always kept a FreeBSD system running at home so that I could perform various network tasks and automate things. In an effort to conserve power and reduce noise, I have been using my trusty Sony z505sx (pictured above). Recently, I switched to a Jetway MINI-ITX board and have been quite happy. The board runs a 1.2GHz Via C7 Eden processor, is fanless and consumes only a few watts of power while operating. It is loaded with 1GB of ram and a 750GB SATA (also low power) drive to provide ample storage. Since the system has RCA/S-Video out, I added a 5″ LCD screen on the top. So far, the machine performs well running as media/web/ftp/ssh server and is barely audible with no fan attached.

I am manufacturing a custom case for this machine and will post a full writeup once I have a cover that I like, for now, you will have to enjoy the single image below. As far as the z505sx is concerned, I decided to put it on eBay in a preemptive spring cleaning effort and to avoid clutter.

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