Ben's Blog

A week ago I attended BSides Winnipeg 2015, a local security conference. There were a ton of great talks and lots of interesting people there. The food was pretty good too.

The recordings of the talks recently went up. Among them was a talk that I gave on the relatively new programming language Rust. It was a lot of fun and I hope I can do it again soon.

If you would like a copy of the slides, you can get them here. My talk was heavily inspired by Memory Safety in Rust by Nicholas Matsakis. If you want to learn more about Rust’s memory safety features, I highly recommend checking out his talk.

A couple weeks ago I was fortunate enough to be able to attend the Software Development and Evolution Conference 2012. Since my formal training is in engineering, I never got the chance to learn a lot of software development techniques. This conference talked about a lot of stuff that falls under the umbrella of “Agile” development. The core idea is to produce quick iterations with tight feedback loops in order to get a working product out the door faster (and of higher quality) than you could if you tried to build the entire product all at once. There are a number of strategies that were introduced and I’m going to log the interesting ones here, largely for my own future reference.

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For the longest time, the company I work for has been using CVS to track their source code. While it works (most of the time), CVS is widely considered obsolete. A few months back I suggested we switch our source code tracking over to Git, and they picked it up and ran with it. We are slowly transitioning things over.

Git and CVS, while they aim to achieve the same goal, do have some significant differences. In order to ease the transition for the rest of the developers, I ran a few training sessions. I based the majority of my talk on “Git For Ages 4 and Up” by Michael Schwern, a fantastic talk using Tinkertoys to show how a Git repository grows. I didn’t have any Tinkertoys, but I did bring in a bunch of K’Nex, enough for everyone to follow along. I think using something physical really helped keep people engaged a lot better.

If anyone wants me help them out with a similar talk or just wants to chat about Git, I’m always up for talking about it.

Recently I’ve been thinking about how I’d really like to make more progress on my projects and how I feel some amount of accountability would help with that. To that end, I’ve decided to start posting regular updates of my projects! Normally I like to save them up and reveal them once completed, but I think seeing feedback from readers will help to motivate me to continue moving forward on projects that might otherwise sit on the workbench for weeks, plus some people might be interested in the details of my design process (at least I might some day in the future, looking back at these posts).

To start things off, I’ll write my first progress report on my bluetooth Kinesis mod. Earlier this year I wrote about my new-to-me keyboard, the Kinesis Essential. I have a few friends who also have this style of keyboard and one of them asked me if I could convert it to bluetooth for him. We did some brainstorming, ordered some parts, and now I’m ready to start prototyping.

My friend’s Kinesis is one of the newer, USB variants. However, it turns out that the new and old boards just use a common main board and the new ones add a USB hub with an integrated PS/2 to USB converter. Since PS/2 is a pretty simple protocol, we decided to start his mod off there; a PS/2 to bluetooth converter. I later plan to replace the whole keyboard controller in my board for better battery life and mouse integration (and to further confuse people who try to use my keyboard) but that will be phase two of the project.

To get the prototype going, I’m just using an Arduino and a PS/2 socket breakout board from SparkFun. As I’ve mentioned before, I’m an avid vim user. As a vim user (and not a masochist, despite what you might know about vim), I think the Arduino programming environment is terrible, so the first thing I did was set myself up with an alternate environment in which I could stay sane. I added Arduino filetype detection to my .vimrc, found a way to build and upload code using vim’s :make command (I chose the scons method described here), and copied the PS/2 Arduino library (found here) into my project directory since the scons setup didn’t seem to find it in the default location. From there, I loaded up the example PS/2 to serial sketch and got the Arduino to read from my Kinesis! Now I need to get a simple proof of concept for my bluetooth module going and then I just need to blend the two together.

When working on my personal projects, I tend to use as much open source software as possible. Many people in the hobbyist world use Eagle for their EDA tools, which has a free restricted version but is not open. I personally prefer to use the gEDA suite of tools. I like it for its cross platform compatibility and its adherence to the Unix philosophy of “do one job and do it well” allowing tools to be connected in many different ways. This often allows the tools to be leaner, yet more powerful. This can also often make some of these tools a bit harder to pick up.

I was recently trying to add an image to a PCB I was making. Being so modular, gEDA pcb does not have an image import feature but instead relies on the program “pstoedit” to convert PostScript vector images into gEDA pcb objects. I have tried doing this before, but usually ended up with poor results. I finally collected the steps necessary to get repeatable, high quality results, which I will document here for anyone else trying to do the same.

1) Load your vector image into Inkscape (I will assume that you already have a vector image and have Inkscape installed)

2) Ensure your image uses only a single colour: black. All black objects will be added to your pcb object and all empty space will be left empty

3) Convert all objects to paths by selecting each object and using Path -> Object to path

4) Remove all overlapping vector paths by using Inkscape’s merging tools (union, difference, intersection, exclusion, division, etc) found in the Paths menu. If you end up with any paths that are touching (or are even just too close to each other without being joined) you are likely to end up with gEDA pcb carving gaps between them to meet the specified tolerances.

5) Adjust the file size to be appropriate for the scale it will be on the board. I have not yet found a way to reliably re-size the imported image once in pcb, so it is important to get this step right.

6) Save your image as a *.ps (PostScript) file. Make sure the “Convert texts to paths” box is marked. You may also want to have the “Resolution for rasterization (dpi)” setting cranked up to its maximum of 10000, but since the graphic remains a vector through this whole process, I don’t think it will make any difference (I haven’t tried playing with that number yet).

7) From the command line, change to the directory that your *.ps file is in and run a command like this:

$ pstoedit -psarg "-r1000x1000" -f pcbfill -ssp 'inputfile.ps' 'outputfile.pcb'

When I was first doing this, I didn’t add any of the optional parameters and I was using ‘pcb’ instead of ‘pcbfill’. -f pcbfill helps to ensure that the objects generated are solid, filled objects, which they might not be otherwise. -ssp forces things like letters with holes (‘o’, ‘d’, ‘p’, etc.) to convert correctly. The man page warns that this may be CPU intensive, but all the conversions I have done have run pretty well instantaneously. I also found I needed the -psarg “-r1000x1000” to get a good resolution out of the conversion.

8) Open your new *.pcb file in gEDA pcb and see the results. You may need to tweak some numbers or add/remove arguments, but so far this seems to work alright for me. Another option that might allow for a little more flexibility is including -xscale and -yscale flags if your image isn’t quite the right size. It may even help to make the image too large on purpose and the use the scaling flags to condense the resolution (again, I don’t think anything is rasterized during this process so I doubt this will make a difference, but it might be worth fiddling with it, even if I haven’t). You might also want to move the object into the top left corner of the pcb layout so that, in case you load it in a layout that is smaller it will still be visible.

9) At this point, you are ready to load your newly created pcb object into your full pcb project.

This process is not an exact science. Play with it until you find something you like. I have had success leaving out some of these steps too, so there is no need to redefine any defaults. Have any other tips for pcb graphics? Leave a comment!