Getting started with Embedded Systems — 3: Schematic, PCB Design, Manufacturing
In this third article of the Getting started with Embedded Systems series we cover the prototyping of an Embedded System from an electrical point of view. Once you have been able to prototype an idea using a development kit the next step is to design a PCB (Printed Circuit Board) for your specific application. It is a three steps process:
- Schematic
2. Layout
3. Manufacturing
1. CAD Tool (KiCad) for schematic and layout
In order to design a PCB, a CAD tool is required. I would suggest starting with KiCad as it is open source, support many different operating systems and is free. You can download the software here.
Get started with KiCad: tutorials
To get started with this software I would recommend this short Youtube video. This cheatsheet can also be useful.
Symbols and footprints
To design a PCB you will symbols for the schematic and footprints for the layout. You can obtain some symbols and footprints on Snapeda.
Layout
The following guidelines should be followed for the layout of a PCB using a manufacturer such as Fusion Seeed:
Min. tracking and spacing: 6mil
Min. hole size: 0.3mm
Power/Ground: 20 mil
Trace: 8 mil
Size of components
If you are soldering by hand I wouldn’t recommend SMD (Surface-Mount Device) parts much smaller than 0805. You can find the different SDM/SMT component packages here.
2. PCB Manufacturing
Once you have a layout you are happy with, you can generate gerber files. These files are needed to manufacture the physical PCB.
Gerber files generation
To generate the necessary Gerber files in Kicad go to File -> Plot.
Select the options are shown in the following two screenshots.
This process will generate several files such as follow for 2-layer PCB:
Top Layer: pcbname.GTL
Bottom Layer: pcbname.GBL
Solder Mask Top: pcbname.GTS
Solder Mask Bottom: pcbname.GBS
Silk Top: pcbname.GTO
Silk Bottom: pcbname.GBO
Drill Drawing: pcbname.drl (rename to pcbname.txt)
Board Outline: pcbname.gm1(rename to pcbname.gko)
Upload for manufacturing
Zip all the files into a single archive. It is now ready for your favourite manufacturer. I would advise using Fusion Seeed as it is cost-effective: 4.9$/10 PCBs without shipping.
Once, you upload the zip into Seeed, you can use the Gerber viewer to make sure the design is correct.
The next article in this Getting Started with Embedded Systems series will be about different communication protocols such as Bluetooth, Wifi or Zigbee. If you have any question or comment feel free to reach out to me on twitter @cDugue.
