Arduino Due clone based on the Atmel SAM3X8E, KiCAD design

This project is about designing a PCB for the Atmel SAM3X8E with the Open Source layout editor KiCad [1]. The result is a kind of Arduino Due Clone, since the MCU is the same and I also have tried to get a similar pin mapping.

I have until now designed quite some PCBs with Eagle [2] from CADSoft and was happy with the software. But since my designs are getting more and more advanced, I start to get limited by the 8 cm x 10 cm size limitation in the light version. The Hobbyist version would increases the size to 16cm x 10 cm for around 169$. Further it would be nice if one could move around a set of tracks, when a little bit of space is needed for another track. In Eagle one has to move every track individually.

Looking around for alternative PCB software, which does not have these limitations, I found KiCAD, which had improved in the last time, since developers at CERN started to take part in the development [3]. With the support of CERN, KiCAD will have a big future. Already now it goes in the direction of ALTIUM, even if it is not yet there.

Features which made KiCAD interesting for me:
* Hierarchical Schematics
* Unlimited size and many signal layers
* Push and Shove router
* The whole editor makes a very professional impression
* More flexibility in the designs

So I believed in KiCAD and started with the schematic design.

The schematics sheet with the micro-controller is shown in the next figure.
The whole schematics can be viewed as a pdf Schematics

Schematics

After the schematics comes the layout of the PCB. This went very smooth after getting used to the key combinations and functions available. One announcing thing are the different render modes, providing different functionality.
But I expect this to be more uniform in the future.

In the design rules I allowed the following minimal settings:

Clearance 8 mil
Minimal Track Width 10 mil
Minimal Via Pad Diameter 40 mil
Minimal Drill Diamter 0.45mm

These are the limits what I’m able to fabricate at home with my etching process.

At the end the PCB looked the following:

ArduinoDueClone_TOP ArduinoDueClone_Bottom

Very nice is the export of the PCB from KiCAD into a PDF for printing on a transparency.

The two layer PCB was exposed on my light board, developed and etched. Via holes were drilled, small silver wires are pressed into the holes as described in Flat VIAs for double sided PCBs and the whole PCB was tinned as described in PCB tinning including VIA soldering.
The vias which are not under the IC were additionally solder for better/saver contact. Holes for the through hole parts were drilled and the PCB was soldered.

ArduinoDueClone_PCB3 ArduinoDueClone_PCB4
ArduinoDueClone_PCB1 ArduinoDueClone_PCB2

For those who wonder why the USB-B contact is on the wrong side, this is due to an error of the footprint in KiCAD.
This issue is fixed in Rev 2 of the PCB (not etched yet).

The final PCB has a similar pin mapping as the Arduino Due

During soldering the track of pin PC1 loosened from the PCB and Pin PB14 seems to have a broken via under the chip.
The rest of the pins has contact and seem to work as expended.

Differences compared to the Arduino Due Mapping:

PC1: Track loosened from the PCB (only effecting my PCB)
PB14: is dead due to a cold soldered Via under the chip (only effecting my PCB)
PA28 is connected to Pin 10, the Arduino Due has additionaly another output pin connected to Pin 10 – PA28 (digital 77)
PA29 is connected to Pin 4, the Arduino Due has additionaly another output pin connected to Pin 4 – PA29 (digital 87)

Conclusion
For me KiCAD is definitely the preferred PCB editor compared with Eagle and I plan to start future projects with KiCAD instead of Eagle. (Some projects are still started in Eagle)

[1] http://www.kicad-pcb.org
[2] http://www.cadsoftusa.com/
[3] http://home.web.cern.ch/about/updates/2015/02/kicad-software-gets-cern-treatment

Files can be found on GitHub
https://github.com/digibird1/ArduinoDueClone

It can be checked out with:

git clone https://github.com/digibird1/ArduinoDueClone

2 comments on “Arduino Due clone based on the Atmel SAM3X8E, KiCAD design
  1. Doubt

    I´am looking for arduino due clone boards.

    In this case where your clone board does not have the ATMEGA16U2 chip, how it is made the transfer between arduino ide and this board?

    thanks in advance

    • digibird1 says:

      I simply connect a FT232RL USB to Serial adapter to the board via the 5V_Serial pins. Then cyou get a std serial port you can use to program with the Arduino IDE. Have a look on EBAY there you can buy them for a small amount of money and can reuse them for all kinds of projects.

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