μblog: engineering from the trenches

Designing a stable oscillator can be challenging. The first choice is if you want something like a ring oscillator that will switch between two output values at a fixed frequency, or if a sinusoidal output is desired. The basic idea is that the oscillator is a feedback system where the total loop gain has to be greater than (equal to) unity and a loop phase of a multiple of 360 degrees for a ring (sinusoidal) oscillator. This is known as the Barkhausen criteria for oscillation. Here is a small application note from Microchip that outlines some of the theory that I promised to apply a long time ago with some older logic gates.  I will make another post later with some more practical designs employing transistors and logic gates and will hopefully have a interesting design to show off.

( 00943a.pdf )

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For something different, here is Intel’s Microprocessor Hall of Fame. The page chronicles CPUs from the 4004 up until the Pentium M and includes die shots up until the Pentium 4. The page also gives an overview of the achievements of each chip, so it might be good information all together. Finally, the Intel Microprocessor Quick Refecence is worth a look.

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Here is a paper entitled Pole-Zero Phase Maps by Kent Lundberg.  It is a pretty easy read and goes over some basic transfer function analysis with a compensation example. A little bit of MATLAB code is also provided. This could compliment my previous post on filter design.

( csm_pzp.pdf )

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Sumotori Dreams is a game designed for Win32 whose complete executable is less than 96kB uncompressed.  The game was presented at Breakpoint 2007. The machines that they used to run things in the competition are XP SP2 with DirectX 9, so it is not unreasonable to expect that the game hooks into many of the available APIs to generate the graphics. It is also possible that the texture maps could be pulled from the XP installation. Even though this game is smaller in size than most spyware, it is truly impressive how fun it is to play.

( sumotori101.zip ) ( sumotori.zip )

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After thinking about using the NES as a embedded system, I thought about what can be done with the original PlayStation. There is already available information on an undocumented UART in the Emotion Engine CPU of the PS2, so it would be natural to see if something similar was also included in the R3000A-based PlayStation processor. Without any available documentation for the CXD8606, it would be a difficult task to figure out which pins are connected to the UART, providing one exists. Sure there are only 208 pins, but that is a lot of time. Looking at the Toshiba and IDT derivatives of the R3000A, both include a UART. The Toshiba device is also in a 208 pin format and seems to have some promise. That is to say, the pins on the PS1 mainboard that are labeled as ROM address and data in the Toshiba datasheet seem to be going to the ROM, etc. I will test this in the lab later and will hopefully be able to expose the dark underbelly of PS1 games through a serial port.

( tx3907f2ds.pdf )

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I promise this the last in a series of MEMS accelerometers [1] [2]. This chip, the ADXL311, is one of the most recent bi-axial accelerometers from Analog Devices. The fingers in the middle that determine acceleration have a different pattern from the 202. Again, the packaging of the dye has prevented me from using the higher power magnification, above 20x.

( adxl311.pdf )

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I received the formal letter today notifying me that I passed the ESM candidacy exam consisting of six hours of written exams, a written research proposal and an oral defense of the written research proposal. With the semester winding down, I can start thinking about working on some electronics projects in my spare time again. The ones that come to mind, in no particular order are:

• telnet to RS-232 bridge using msp430
• custom code on the NES using reprogrammable cartridge
• adding useful features to Fonera Linux distro
• changing the firmware on some DSL/WIFI routers I have around
• iPod control with msp430/AVR
• something interesting with a Peltier device
• wind-powered battery charger

Comments/suggestions are welcome!

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While thinking about cheap development boards, I remembered my NES (picture from 1up blog).  The system would be ideal for hacking by modern standards as it features a custom 6502 processor from MOS Technologies running at a very accessible 1.8MHz. All of the chips are in PDIP form and the system is pretty cheap. Memory can be wired directly to the ZIF connector used for cartridges, or a reprogrammable cartridge can be made. Finally, system architecture guides are available. Maybe I will open mine up to see if I can tweak anything once Nintendo puts Super Mario Brothers 3 on the Virtual Console.

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Few words can describe the terrible events that unraveled today at Virginia Polytechnic Institute. It is really unfortunate that someone had such a lapse in judgement as to take the lives of fellow humans. Even though there is little known about the gunman, some poor excuses for human beings are already using this horrific event to push their personal agendas.

(Statement from VTech President: mp3)

(Via [1] [2] [3] [4] [5])

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To follow up a previous post in LaTeX, here is an example of a presentation done in LaTeX and rendered to PDF for display in a PDF viewer. The .txt file contains the LaTeX (should normally be named .tex, but .txt might be easier for some web browsers) which generates the output. The LaTeX package I used is MiKTeX and the editor is simply called “LaTeX Editor”. The presentation macro is called powerdot. The one tricky part was including some graphics. To make things easier, I converted the images to PDF and then included them as shown in the code. If LaTeX complains about bounding box on the images, the solution is to open the PDF in LaTeX Editor and look at the first page or two where you see a MediaBox entry followed by four numbers. Those are the numbers copied into the includegraphics directive after bb=.

( proposal.pdf ) ( proposal.txt )

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