Archive for January, 2011

Creating a custom Fritzing part for the Dwengo board

A problem I always have with my robots is they end up as a messy spaghetti monster with lots of wires leading to hidden places on the robot. When (purely hypothetically) the robot bumps into a wall some wires get loose and I have to figure out what was connected to what again.

I should keep some documentation on my robot. I wanted to do this with Fritzing, a cool open-source program for drawing breadboard-prototypes and more. Lots of parts are already available in Fritzing, like an Arduino, a servo, chips, and so on. As the Dwengo board was not yet available as a Fritzing part, I created it myself.

A Fritzing part is composed of SVG vector graphics: one for the breadboard layout, one for the schematic layout, one for the PCB layout, and one for the icon. These graphics can be created in InkScape. I never worked with InkScape before, so I had a hard time drawing the breadboard layout. The easiest way to create the layout was to take a photograph of the board, then import that in Inkscape, and draw over it. I reused the svg images from the existing Fritzing core parts to create the final layout.

Because Fritzing has to know which part of the image is a connector where wires can start and end, one has to create connectors. This is done by creating rectangles with the names connectorXterminal and connectorXpin (where X is the connector number). In the schematic and PCB layout, the same connector have to exist with the same name. This way, Fritzing can keep the three layouts in sync, so if you create a prototype in the breadboard view, you immediately get a schematic view and a PCB view.

For the SVG files of the schematic view and the PCB view, I started from a header row (for the schematic view) and from a regular chip (for the PCB). Once these were done, I created the part in Fritzing:

In the parts editor, you can label all the connector pins and give them a description. You can also add and remove connectors if necessary. As you can see from the image, I created connector pins for the Dwengo connector on the left, and for the driver chip output on the right. The pin labels mention the PIC pin number and the corresponding Pinguino pin number (see https://kr3l.files.wordpress.com/2009/12/pinguino.gif).

Download the Fritzing part.

Now that the part is created, the fun can start :-). It only takes about 5 minutes to redraw my robot schematic in Fritzing. One problem I had was that the Bluesmirf component doesn’t exist in Fritzing, but I used a “mystery component” with 5 pins instead. The resulting prototype is shown below:

As you can see, this is a nice and  easy way of creating a breadboard prototype of your project. You can download this diagram from its Fritzing projects page. Fritzing features a lot more cool features, like automatically create a parts list, create an etchable PCB layout or Gerber files as a Pdf, …, which help you in sharing your project with others and in going from a prototype on a breadboard to a real product on a PCB!

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January 8, 2011 at 10:10 pm 4 comments


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