Easy-phi: an Open Source Platform for Experimenters

As a few of Hackaday readers may already know, my day job involves working with high speed electronics. For the last few months, my team at [Université de Genève] in Switzerland has been working on an open source platform (mostly) targeted for experimenters: the easy-phi project. The main idea is to build a simple, cheap but intelligent open hardware/software platform consisting of a 19″ frame (or smaller), which can house a big variety of electronic modules. Hobbyist would therefore only make/buy the modules that would suit their needs and control them through a web page / standalone application / Labview module.

I detailed in more depth on my website the technical aspects of the project. To give you a quick and simple overview, the rack is essentially a USB hub that connects all the modules to a Cubieboard. It also integrates a few synchronization signals, a clock and a monitoring system for voltages, temperatures, power consumption. The modules are made of template + module specific electronics. The template electronics are part of the ‘easy-phi standard’, they consist of the Arduino compatible SAM3X8E microcontroller and of a few other power related components. This ensures electrical and firmware compatibility between the rack and modules that you guys may develop. It is important to note that the modules are enumerated on the USB bus as composite CDC (communication device) and MSC (mass storage). The CDC is used to configure the module while the MSC allows you to grab its documentation, resources, and standalone application in case you use the module without the rack.

The chosen schematics / layout software is Kicad, and all current files can be found on our github. Others will be uploaded once we have tested the other modules currently in the pipe. As the ones we’re developing are physics oriented, we hope that enthusiasts will bring easy-phi to other domains. Don’t hesitate to contact us if you have any question or if you’d like to contribute.

Creating Irregular Board Outlines in KiCad

irregular-borders-in-kicad

One of the benefits of plain text file format is that you can go in and edit them by hand. This is part of the KiCad board outline hack which [Clint] wrote about in a recent post. He wanted a unique board outline, which is something that KiCad isn’t necessarily well suited for. His solution was to create the outline as an image, then import it. If you’re wondering what custom shape is called for this type of work we’d like to point you to the (kind of) bottle opening HaDuino. That PCB layout was done on Eagle, which has a bit more leeway with special shapes.

Before getting to the code editing step seen above [Clint] used the built-in feature for KiCad that will turn an image into a component. He exported that code and altered it using a text editor in order to change the layer setting for the shape to that of the board outline. This took him from a plain old image, to a module which can be selected and dropped into the board editing program. It’s a snap to do this sort of thing for the copper layers too if you’re interested in using your mad graphics editing skills to layout an art piece on copper clad.

Turning PCBs into art

board

Designing a circuit, laying out a board, and sending it off to be fabbed is so easy anyone can do it. A lot of people are, in fact, and with the traditional tools like KiCAD and Eagle, a lot of different boards look very, very similar. You could always add some cool silkscreen graphics to your board to make it stand out, but [Saar] has a better solution: it’s called PCBmodE, and it allows you to draw circuits artistically instead of the 45° angles we’ve become so accustomed to.

PCBmodE takes the parts, pads, signals, and vias for boards stored in JSON files and converts them to an SVG representation. The file is then routed (manually, but [Saar] is working on automated routing) and Gerberized so it can be sent off to a production house.

You can grab PCBmodE over on bitbucket, but right now it’s still a very early version. Vias and copper pours are working, but [Saar] has only fabbed this board so far.

Assigning new packages to Eagle PCB components

adafruit-eagle-component-creation-tut

If you’ve spent any time at all laying out your own circuit boards we’re sure you’ve run into the issue of not having the right component or package available in the standard libraries. If it’s a common part, chances are the symbol definition will be there.  But perhaps the footprint you want to use is missing? Here’s an easy to follow tutorial which demonstrates how to assign new packages to existing Eagle PCB components. It even shows the basics of how to tweak the footprint to fit your needs (like making SMD footprints easier to hand solder).

This will not teach you how to make your own custom symbols, or how to build packages from scratch. But it will let you locate the package you want to use from a different component, then copy it to your own library for use with different parts. And the techniques shown make this a quick and relatively painless process.

We certainly don’t want to start another comment quagmire like the recent PIC v. AVR discussion. But we’ve used both Kicad and Eagle rather extensively and feel that neither one has really mastered part/footprint creation in a user-friendly way. We like Kicad’s total separation of footprints from components, and it’s myriad of parameters which can be used to tweak the layout. But if you use the same components frequently, Eagle’s standard of linking parts and footprints does end up saving a lot of time. What do you think?

Automated PCB panelization

panel

Some PCB production houses – Seeed Studio and itead studio, especially – allow you to upload a gerber file and receive a printed circuit board very inexpensively. The pricing structure for these board houses is based on predesignated board sizes – 5cm square or 5×10 cm – and sometimes a project is just too small to justify buying a full 25 square centimeters of board. This is where panelizing comes in: by putting multiple copies of a circuit board on one of the available sizes you can get more boards for the same amount of money. But how to panelize your boards without the (sometimes) hassle of cutting and pasting?

[Martin] came up with a way of panelizing PCBs with just a Python script. By creating one copy of a circuit board in KiCAD, he can fire up his script and tell the computer exactly how to duplicate his circuit to fit any size board.

By his own admission, [Martin]‘s script is still a little clunky, but it does allow him to edit the panelized board in KiCAD and also copies the nets so the ratsnest doesn’t go between boards.

Toorcamp: Milling PCBs With KiCad

[Hao] from Noisebridge showed me their CNC mill being used to etch PCBs. Using copper clad board, this MAXNC 10 mill routes the PCB with decent accuracy. This makes for very rapid prototyping of single sided PCBs.

[Hao] designed the PCB using the open source KiCad EDA tool. This was used to draw the schematic, layout the PCB, and generate the Gerber files. Next, pcb2gcode was used to convert the Gerbers to G-code, which is a standard set of instructions for controlling CNC devices. Finally, LinuxCNC was used to send the G-code instructions to the mill. It’s a powerful application of a completely open source workflow.

The PCB being milled is for a pressure based touch sensor. It uses the Freescale MPL115A barometric pressure sensor encased in a rubber housing. This sensor is being incorporated into the Dora Opensource Robot Assistant project, which [Hao] and the Noisebridge folks are working on. We’re looking forward to hearing more about the Dora project in the future.

Kicad symbol generating script shows promise

Kicad is a fantastic PCB layout tool. We think creating a part for use with Kicad is in many ways easier than in Eagle, but it never hurts to have a few shortcuts. Here’s a new way to quickly get your parts into the schematic editor. It’s a Python script that generates symbols from an XML input file. You create the XML file with a list of all the pins on your part and the function they will serve. The Python script will then format that as a library file which can be imported by Kicad.

It’s a little bit clunky due to the number of steps in the process. But it is possible to use a CSV file generated in a spreadsheet program to create the XML needed by the script. We’ve used the online component builder ourselves, and appreciate the possibility of mass pin assignments instead of the drop-box for every pin as used by the web interface. One time we were 20 pins into the naming process and accidentally refreshed the page… ugh!

The code is available in their git repository, with a description of the XML format, and a wiki tutorial outlining the component building process. After you give it a try we’d love to hear what you think in the comments.