Ben's Blog

It has been a while since my last post. Lots of stuff going on. Here’s a quick summary.

Earlier in the year I was elected to the board of directors at SkullSpace. It is really great to see all the things people are doing there and to be a part of making that happen.

For a while now I’ve been working on a bit of a side business. The idea is that we will develop, manufacture, and sell open source electronics. Ultimately, we intend to sell them with a pay-what-you-want model (with minimums) as well as pay-who-you-want (ie. allow the customer to direct where they want some of the profits to go; designer, influential projects, charities, etc). If you are interested, you can sign up for our mailing list on our website.

One of the first products I’ll be posting is an RGB LED ring display for a rotary encoder. Additionally, it adds capacitive sensing to the encoder so it can tell when the user is touching the knob. The firmware is still a work in progress, but I made a simple demo video to showcase the basic features.

RGB Rotary Encoder Display Demo from Benjamin Bergman on Vimeo.

Introducing the μJoypad, the worlds smallest NES controller! Measuring in at 25.4×12.8×3.2mm (1.0×0.5×0.1in) this is, by my best research, the worlds smallest, fully functional NES compatible controller. A couple months ago I saw an article or video of the world’s largest game controller and thought to myself “I bet I could make the smallest” and so I did. The project is open hardware and available on GitHub. More pictures and a description of the design process after the jump.

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Last weekend my wife and I made ourselves made a new coffee table (well, more like we helped my dad make it for us). As you can see, our table comes with a door knob, a relic from its past life. A few weeks ago we stumbled upon another’s efforts to repurpose a door into a table and decided to try for ourselves.

My father-in-law already had some old doors sitting in his basement, but they were single panel doors. In order to get a cleaner look I decided that we should miter the cut and make the table look like it had just been folded over.

Since we have a rather long couch, our original idea was to use two doors: one for the table top and one side, the other for a shelf and the other side piece. However, after measuring to see how much longer this would make the table, we realized that we would only gain about 15 cm as we would still be cutting off the top and bottom to get us our folded look. Once we added in the fact that the second door was in much worse shape and was actually slightly narrower, we decided the extra effort wasn’t worth it so we ended up just using the one door.

At this point, we were still thinking we wanted a shelf and possibly also feet. One advantage of using a single panel door over a multi-panel door is that the height is much more flexible. We aimed to have the height of the table be slightly shorter than the couch seat height to allow for the addition of feet, but after a minor measurement error, we ended up with the table being almost the exact height of the couch. This turned out to be a blessing as, once we had the table assembled, we realized that we liked the looks of the table without feet or a shelf.

The one down side to using a single panel door is that the centre panel is not very strong, but it makes up the majority of the table top. In order to help solidify the top in case someone decides to sit on it or something, we added a few 2×4 support pieces to the underside of the table.

So far we have decided not to add a shelf as the look of the table is currently quite clean and has enough room for us to store some baskets full of board games. We still have some finishing work to do (fill in some of the joints and screw holes with wood filler, re-stain the heavily sanded corners and support beams, etc) but for now it is in service and we are really enjoying 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!