Build an 8-Bit Heart with MeowCAD

At some point, after you design your schematics and boards, you want to submit them to be fabricated. Whether you use MeowCAD or some other tool, the workflow is pretty similar. We live in a pretty amazing time where this can be done for reasonable cost with only a few weeks delay. Not even 5 years ago, this was a costly ordeal. Sometimes small electronics would order 500 boards at once and hope for the best since the cost of ordering so many more was negligible compared to the overhead cost of ordering a single prototype.

We’ll be focusing on submitting the 8 Bit Heart Gerber files to OSH Park for fabrication. We’ve heard Dirt Cheap Dirty Boards is a decent service that is very affordably priced but we haven’t had a chance to use them. We’re hoping to make sure our Gerber file generation is robust so we’ll be submitting to some different board manufacturer houses but so far we’ve only gone through OSH Park.

Very roughly, one workflow is as follows:

• Design your PCB. We’ll skip this step and use the 8 Bit Heart project ready in MeowCAD.
• Collect the Gerbers. The export from MeowCAD includes them but we’ll need to collect them for later submission.
• Submit to the board Manufacterer. We’ll be using OSH Park.
• Assemble. We won’t go into too much detail but briefly outline a “DIY” way to do this.

As a quick aside, a snippet of an example Gerber file that we’ll be submitting looks something like this:

...
G04 Gerber Fmt 3.4, Leading zero omitted, Abs format*
MOIN*
FSLAX34Y34*
G01*
G70*
G90*
G04 APERTURE LIST*
ADD12C,0.0000*
ADD13C,0.0032*
ADD10C,0.0640*
...
ADD19R,0.0177X0.0787*
G04 APERTURE END LIST*
G54D12*
D10*
G01X22700Y-03900D02*
G01X22700Y-03900D01*
...

For those familiar with G-code, the files might look similar. It’s a textual representation how to draw geometric primitives. The APERTURE LIST section holds the primitives (C for circle, R for rectangle, etc.) after which the draw commands are issued with move commands (e.g. G01), specifying which of the apertures to use. For example, in the snippet above, %ADD10C,0.0640*% creates an aperture named D10, a circle of radius 0.064. Later, the aperture is specified with a D10* line and the draw commands are issued via G01X22700Y-03900D02* et G01X22700Y-03900D01* move the pen to x 2.2700 y -0.3900 and then ‘streak across’ the circle to x 2.2700 y -0.3900. The %MOIN*% directive specifies the units in inches and the %FSLAX34Y34*% specifies that the X et Y co-ordinates are given as 3 digits for the integral part and 4 digits for the fractional part. For more details feel free to check out the Gerber specification document.

Probably way more detail then you wanted to know but it’s sometimes nice to know that there’s nothing magical going on underneath. It’s just a textual representation of the geometry that we want to produce.

Let’s download the 8 Bit Heart project. If you hit the Download button, this should download the project with all the relevant files (be patient, sometimes it takes a while).

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