Open hardware start

[siriusf]

Hi, I have been working with arduino and PICs for sometime and I have a basic knowledge on electronics, programming and computers. I want to know what information (text books, whitepapers, articles) did you need to design a board like OLinuXino from a SoC? the process of designing electronics boards for a SoC's like Allwinner A20 is similar to the process of designing boards for microcontrollers? How much time takes to design such a board?

[dave-at-axon]

Designed a board like the A20 is not going to be something someone who dabbles with Arduino or any other low speed processor is going to be able to do without extensive knowledge of high speed design and multi-layer PCB's.

This processor is running at 1GHz or higher.

Download the Eagle files and have a look at the connections from the CPU to the RAM and you will see some nicely squiggly lines connecting them. This is to keep tight timing and if you don't know how this works, your going to end up with a board that does not work.

If on the other hand you design PCB's for a living and understand multi-layer and high speed then it should be easy to work with the open source designs to create your own.

I design PCB's for a living but have never done any high speed designs before but looking to try and build a custom board using the A20 design so that I can fit it all on one board. It's a brand new learning process but I do have multi-later PCB design skills but the high speed is all new.

[JohnS]

^^^ N.B. "later" = "layer"

Yes, definitely not a task for a beginner.

Also, likely to need rather high-speed electronic tools to debug when it doesn't work reliably.

PCB traces are delay lines, impedance matters, reflections are nightmares, don't forget cross-talk and so on.  Not for me!!

John

[dave-at-axon]

@JohnS. I've got Altium Designer and I found this very good tutorial on high speed design and I am plodding my way through this as I input the schematic and parts for the A20 board.

http://www.fedevel.com/welldoneblog/2011/06/altium-designer-high-speed-design-tutorial/

[JohnS]

Have fun

I expect you know lots of the AW tablets and boards don't work reliably (I guess you've seen posts on linux-sunxi) due to dubious RAM etc timings except at reduced speeds and bigger delay params (the 1GHz ones rarely if ever are shipped at that speed) but I suppose their designers also used suitable tools...

John

[siriusf]

Thank you for the answers, I don't really want to make a new board starting from the Allwinner SOC, i just want to be able to take one of the olinuxino schematics, remove some of the ports, and add a specific cellular modem. I would like to be sure that the pcb is correct and ready for production.

[JohnS]

Well all the best of luck.  I wouldn't try it but you may get lucky.

Have a Plan B in case it doesn't work.

John

[dave-at-axon]

I just want to be able to take one of the olinuxino schematics, remove some of the ports, and add a specific cellular modem. I would like to be sure that the pcb is correct and ready for production.

Then why not use the existing Eagle based Olimex board design and remove the parts you don't need and add what you do need. You can then leave all the highspeed stuff as it is.

Unless of course you want a different board shape but even then you can just copy and paste or create a new board outline. I am considering this option too after importing the design into my CAD system. The A20 design would be in the middle of my board and the IO would be arranged around the outside of this doing away with the GPIO connectors. My board size is larger than the A20 so this idea may well work for me.