μblog: engineering from the trenches

I recently found another free tool (in addition to LASI) that allows users to play around with CMOS layout (and some very basic simulation). The tool is from Microwind Inc with the lite version aptly named “Microwind“. Once the user form is filled out with minimal information, various tools can be downloaded with an assortment of papers including a 4-bit microprocessor example. The lite version of the tool is somewhat limited, but there are some simple layout examples. Furthermore, this is the tool used to demonstrate all of the examples in Basic CMOS Cell Design (Amazon) and Advanced CMOS Cell Design (Amazon) by Sicard (author of the software) and Bendhia. I have read most of the first book and am working on the second one and will write a short review when both are completed. So far, the first (Basic) one is all-right for a reference but requires some thinking to understand a few of the layouts. The image above is a example layout for a 3-bit DAC.

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Although SPICE is one of the most prevelant tools for analog circuit simulation, saying that it was without problems would be incorrect. The problem that I have seen is that individuals start using a cad package, such as the Cadence/Orcad suite and run into some incomprehensible problems with analog simulation with PSPICE and quickly give up on the technology deeming it unusable. What needs to be understood is that the simulation heavily relies on numerical integration and matrix inversion methods, both of which are very susceptible to numerical errors. The up-side is that there are parameters that can be tuned, and in some cases, simulation speed/performance can be sacrificed to get higher accuracy and convergence.

Charles Hymowitz, from Intusoft, has written a small article on the topic of SPICE simulation convergence. The basic idea here is to first make sure your circuit is wired as intended and that the nodes are properly labeled. He then gives an overview of some parameters and algorithms that can be tweaked to try to attain convergence. Finally, he makes a very important point: if your circuit still doesn’t converge, look back at the design, there may be something inherently wrong with it.

I agree with most of his statements and have been using SPICE for some time to get a high-level simulation of various analog circuits. Unfortunately, it is not a substitution for building a prototype, but it does offer assistance with initial design. I am thinking of writing up a few step by step guides for using the Orcad suite, including one that demonstrates PSPICE simulation with device models downloaded from vendor web sites. If anyone is interested in seeing those types of things, send an email or leave a comment and I may do it a bit quicker.

( converg.pdf )

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For one reason or another, both of the shift keys suddenly stopped working on June’s VAIO notebook. After some troubleshooting it seemed to be a hardware problem. With work needing to be done, I didn’t want to open the machine up and risk breaking more things so I thought that it would be easiest to remap the shift key to the caps lock key, one that shouldn’t be used too often. While it is straightforward to change this on a Unix/Linux system (xmodmap, loadkeys, etc), it turns out that there is also a straightforward method to do this on Windows. This requires editing the registry, however, the Windows Resource Kit has a nice graphical front-end to do this.  The installed tool is called remapkey.exe and has a drag and drop configuration screen. Long story short, the caps lock key is now the shift key, and everything is fine until tomorrow.

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It is now official:

To our valued OrCAD Layout customers:

As demonstrated in the OrCAD® product 16.0 release, Cadence® continues to invest in providing a fully scalable PCB design solution for our customers – one that grows with you as your PCB designs grow in complexity. We’ve all seen the PCB design landscape change dramatically in recent years. In order to help customers meet current market demands and maximize productivity, Cadence continues to leverage the power of its proven Allegro® PCB technology within our OrCAD product line. This allows Cadence to offer customers unique suites and technology bundles that address current and future design challenges.

This letter is intended to communicate some important developments regarding the future of Cadence OrCAD Layout. Cadence has begun the End-of-Life process for Cadence OrCAD Layout technology based products.

Please Note: Cadence OrCAD Capture, OrCAD Capture CIS, and PSpice® technology are all integral parts of Cadence’s long-term product strategy and are not affected by this notice.

Effective July 31, 2007, Cadence will no longer sell the following Cadence OrCAD Layout based technology products:

1. OrCAD Layout (PO1410)
2. OrCAD Layout Plus (PO1420)
3. OrCAD Unison PCB (PO1510)
4. OrCAD Unison Ultra (PO1530)
5. Layout Studio (PS1430)

We acknowledge that transitioning software systems is never easy and is often a juggling act between investing in learning new technologies and meeting current business priorities. EMA is committed to ensuring we do everything possible to help minimize the impact on you, wherever possible. To help ease the transition, Cadence is providing OrCAD Layout customers with multiple paths for migrating to new technology that leverages the power of Allegro PCB Editor. Learn more about the various transition path options by visiting http://www.ema-eda.com/orcadlayout.

The products entering End of Sale will be supported thru March 31, 2009. After that date, these products will no longer be supported for hot-fixes or support calls and will not be shipped on the OrCAD CD set.

If you have any questions, or would like to discuss these changes and how it may impact you, please contact your EMA Account Manager. You may also contact the EMA technical support team at 585-334-6001, Option 5, or by email at techsupport@ema-eda.com.

We remain focused on providing solutions to ensure your ongoing and future success!

Best regards,
Manny Marcano

President and CEO
EMA Design Automation

Many people saw this coming as virtually no new features have been added to Layout in the past four years, only bug fixes. Although Allegro PCB Editor is a little bit more pricey, I think its worth it, especially for high performance designs. Finally, the Layout site gives some instructions on migrating. Layout,… we have had some great times together:

• The great and unavoidable crashes that used to occur when the user would lock the (win32) workstation running Layout
• All the excellent times that Layout would close your design without saving if you hit CTRL-C twice instead of once
• Layout’s inability to recognize artwork that was placed on the Global Layer (0) when creating Gerber files

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One of my colleagues was experiencing some problems with Microsoft Entourage and wanted to switch to Mozilla Thuderbird but had to also transfer the “local folders”. Entourage was crashing every time the email login was entered and would not permit us to copy the local files to an imap server in order to retrieve them inside Thunderbird. After much searching, I found that if the folders under Local Folders/Documents are simply dragged onto the desktop, or any other folder in that case, the come up as .mbox files and conform the mailbox standard. These .mbox files could then be directly copied to the Local Folders section of the Thunderbird profile (~/Library/Thunderbird/Profiles/x.default where x is something random). The .mbox suffix was then removed and a .msf file was created for each of the directory files using a script. The .msf file only display information and does not need to be specific for each file. Thunderbird was then restarted and all of the copied folders appeared under Local Folders.

This may seem trivial to most people that use Macs on a regular basis, but I figure I should document this for the one person who may end up in my position lacking substantial OS X experience.

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One of my annoyances with the default settings in LabView is that it places all terminals on the front panel as icons in the block diagram view. These icons are large and tend to push stuff around when they are created automatically. Every time I have to re-install LabView, I figure out how to disable this feature only to promptly forget it. This time around I will record the simple fix to save myself time in the future. The setting can be disabled by going into the Tools -> Options screen in either the front panel or block diagram. Block Diagram is then to be selected from the left side and Place front panel terminals as icons must be unchecked from the right side. Now your block diagram is safe from bulky icons, until the next LabView upgrade that is.

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Hide the children and lock the doors, Phrack #64 is available. This news is a few days late since I didn’t pay too much attention to the security mailing lists this weekend, nevertheless, better late then never!

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For a long time, I thought printing to PDF was limited to those owning Adobe Acrobat Professional. I was pleasantly surprised to find out that there is a free tool aptly named PDFCreator.

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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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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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