Two Layer Gerber generation in Eagle Light

           When you’ve finalised your design, the last step before sending it off to the fab house is to generate gerber files. Gerber files are kind of a “universal language” for PCB designs. EAGLE is far from the only PCB CAD software out there, and its design files are nothing like those of Orcad or Altium. Fab houses can’t possibly support every piece of software out there, so we send them the gerber files instead.

Gerber files – note the plurality – each describes the single layers of the PCB. One gerber might describe the silkscreen, while another defines where the top copper is. In all, we’ll generate seven gerber files to send to the fab house.


CAM Processor

Before we get too much further, you’ll need to download another definition file: SparkFun’s CAM file.

Then, load up the CAM processor by clicking the CAM icon – 12 – which will open up this window:


Go to the File, then Open > Job, select the sfe-gerb274x.camfile that you have downloaded. Now the CAM processor window should have a series of tabs: “Top Copper”, “Bottom Copper”, “Top Silkscreen”, etc. Each of these tabs defines how to create one of the gerber files. Now all you have to do is click Process Job. If you haven’t saved recently, it’ll prompt you to.

The gerber generation process should be pretty quick. Once it’s run its course, have a look in your project directory, which should have loads of new files in it. In addition to the board (BRD) and schematic (SCH) files, there should now be a .dri, .GBL, .GBO, .GBS, .GML, .gpi, .GTO, .GTP, .GTS, and a .TXT. Meet the Gerbers!

You will now see some tabs in the CAM Processor. Each of these tabs will generate a Gerber file.

Gerber File Extension
Bottom Copper GBL
Bottom Silkscreen GBO
Bottom Soldermask GBS
Top Copper GTL
Top Silkscreen GTO
Top Soldermask GTS
Drill File TXT
Drill Station Info File dri
Photoplotter Info File gpi
Mill Layer GML
Top Paste GTP


The very first step is the Top copper side i.e. .GTL file; this is the top copper layer. The following layers must be active

  1. Top
  2. Pads
  3. Vias
  4. Dimension



The next step is the bottom copper side i.e. .GBL file; this is the bottom copper layer. The following layers must be active

  1. bottom
  2. Pads
  3. Vias


Silkscreen is normally used on the component side to identify components, test points, PCB and PCBA part numbers, warning symbols, company logos and manufacturer marks.


Silkscreen is the name that appears on the PCB, here it will be bottom


Solder mask or solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads.



The last step is generating drill data .drd where in only drills and holes must be active

Finally you can view all the files in gerber viewer software