Tag Archives: Eagle

OSHW Logo Announced, Eagle ULP available

On Thursday, the OSHW folks announced the results of their logo selection process.

The logo shown above, created by Macklin Chaffee, will soon become a regular feature of OSHW designs.  You can expect to see it silkscreened onto printed circuit boards, CNC-cut into metal enclosures, and laser engraved onto just about anything.

It has been interesting to see OSHW supporters scramble to translate the logo into their preferred formats, including SVG (more variants here) and gEDA.  It’s also interesting that the logo is so new that there doesn’t seem to be any consensus about how it should be displayed – filled or outline, with text or without.

Eagle users can thank Westfw for creating an Eagle ULP that will draw the OSHW logo with a configurable outside diameter.  There is more information about the ULP on the OSHW forum.  I haven’t tried it out yet, but I’m looking forward to adding the logo to my own open source hardware designs.



Cadsoft Eagle Support Forums

Twitter users, sorry for the link spam, but I thought this was valuable enough to stick up on the blog!

Anyone who uses Eagle will be happy to know that Stratford Digital is hosting a web forum version of the Cadsoft support newsgroups.  In their native format, the Cadsoft newsgroups require an NNTP newsreader – hats off to anyone who actually has one installed these days (I use MT-NewsWatcher on the Mac).

EAGLE Enterprise Toolkit Forums

gerbv – A free, open source gerber viewer for Linux / OS X

When you finish a PCB design, you typically use the CAM export function of your layout tool to generate a set of gerber files to send to the PCB manufacturer.  To avoid errors in the finished board, it’s usually a good idea to review the files before you click send.

Enter gerbv, a free, open source gerber viewer that is available for many platforms, including Debian and OS X (via fink).

I recently upgraded to version 2.0 (I was using the really outdated version 1.0 on Macports) and I am really impressed by the improvements in the GUI and overall usability.

gerbv is a part of the gEDA suite, which also includes layout and schematic capture tools that are slowly becoming more popular vs. more established non-free tools like Eagle.

Update: I missed an interesting update to a post over on My 2uf, not everyone seems to like the rest of the gEDA suite.

gerbv screenshot
gerbv screenshot

AVR HV Programmer Shield in the Works!

AVR HV Programmer Shield PCB Layout

What’s this???

In response to the continued demand for a PCB version of my Arduino-based AVR High Voltage Programmer, I just released a first cut to BatchPCB and should have a prototype within 3-4 weeks.

This design is an improvement upon the original HV programmer shield in the following areas:

  • Onboard 12V boost converter eliminates the need for an external 12V power supply
  • Support for two of the most common families of AVR microcontrollers, the ATmega48/88/168 and ATtiny2313
  • Separate Ready and Burn indicators
  • Protection resistors on every single data, control, and supply line to the target AVR, meaning that your Arduino and AVR should survive any mishaps during programming, including inserting the AVR backwards or off by 1 pin.

I hope to have kits for sale in early February.  Sorry for the delay in getting these made, but I wanted to make the best possible shield I could!

Free IPC-7351 Land Pattern Calculator

Let’s say you are designing a printed circuit board in Eagle, and you need to place a component that you’ve never used before.  In Eagle, before you can use a new component, you need a land pattern, a schematic symbol, and a mapping between them to fully define the part.  Often, you can search through Eagle’s included libraries and find what you need (or something close enough).  But what if that fails?

The symbol and pin definitions are usually pretty easy – just copy the datasheet.  The hard part is the land pattern: the collection of copper traces, soldermask openings, silkscreen, and other features that define the part on the PCB.

To come up with a land pattern, you usually have a few options:

  1. Someone else may have done you a big favor by creating a part definition and uploading it to the Eagle library directoryCaveat: Use it at your own risk.  Surface mount parts tend to be particularly hard to use right out of the box – often someone else’s land pattern won’t even pass your DRC.  Whose process were they using, anyway??
  2. Look through the datasheet for the part to try and find a recommended land pattern. (Good luck!  Increasingly these are not included, but may be somewhere else on the manufacturer’s website.  Google is your friend!)
  3. Take a guess based on the geometry of the part, assuming you have a mechanical drawing or a physical sample somewhere.
  4. Skip 1-3 and use an IPC-7351 land pattern generator.

IPC-7351 is a standard for printed circuit board land pattern designs.  The standard attempts to, well, standardize land patterns to try to discourage every PCB designer from having his or her own custom library of land patterns.  IPC takes known good land patterns and combines them with accepted manufacturing tolerances to produce a land pattern that will work for most people most of the time.  Increasingly you will see references to IPC-7351 in datasheets instead of a land pattern drawing, so access to the standard is becoming more important over time.

Cool, right?  Well, the bad news is that while you can browse through the table of contents/introducton for free, downloading the standard costs big bucks.

Fortunately, PCB Matrix has a free IPC-7351 Land Pattern Calculator (direct download link here) that you can use to generate land patterns based on the standard.  You don’t need to own a copy of the standard to benefit from it.

The calculator is somewhat tricky to use but if you click the right buttons you can get something like what is shown below (click to enlarge).

Thin SOT23 8-pin Package Land Pattern Screenshot
PCB Matrix IPC-7351 Land Pattern Calculator Screenshot

X and Y are the dimensions of the recommended pads for an 8-lead Thin SOT-23, which happens to be the package for the LT3464.

With this information, you can return to Eagle and create a land pattern for your device.  PCB Matrix will also sell you premade Eagle libraries, but from their site it was not clear how much they cost.  Based on their other products, my guess is several hundred dollars and a yearly maintenance contract – I’ll draw my own, thanks.

Unfortunately, the calculator is Windows only, so Mac guys like me need to use VMware Fusion or similar to use it.  Can someone create a web version, please?