[Arm-netbook] KiCAD based A10 break out / prototyping PCB finished

[jm]

On Wed, 2013-02-06 at 17:33 +0530, Ajith Kumar wrote:
> 
>         
>         
>         Firstly Ajith, anyone can download KiCAD
>         http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software
>         +Suite
>         learn it, and do the modifications and upload it, make it,
>         sell it etc.
>         Its all GPL'd - so no need to wait around for approval
>         from anybody. :-)
> 
> Tried it, but the Kicad version 0.0.020110616-1 (on Ubuntu12.04) says
> a new version is required.

The latest version for Ubuntu is here:
https://launchpad.net/~adamwolf/+archive/kicad-testing-daily

Need to follow the instructions for using ppa method to update the
KiCAD.



>  Looked at the Gerber files. What are the bare minimum addition
> required, apart from A10,  to get a blinking LED program going. Power
> source & TF socket is enough ?

Not having built it yet, and not having had time to investigate fully, I
am out of my depth but here goes:

1. Need to a fex file ready and then get the fex file loaded into the
A10. This is done by using the fex loader which Allwinner release and is
available from sunxi web site http://linux-sunxi.org/Main_Page
I believe some sort of USB to TTL serial link also needed into the CPU
to get the windows program to talk to the A10. The fex file tells the
A10 to boot from TF card, and boot the uboot boot loader from there.

I am not sure this step is needed - but some expert can correct me on
this.

2. Then I think it needs uboot on the TF card - probably any uboot would
do is the assumption. Once uboot starts up, stop it from running by
pressing any key on the serial link.

3. Some kind of program needs to be on the TF card that can then be run
by uboot to blink the LED. This is something that can be written in C
and compiled from gcc from a working mk802 or similar A10 cpu board that
has gcc installed. It should be compiled so as not to need Linux to be
running. Uboot can be instructed to load that program into RAM and run
it. That assumes you got RAM! I'm not sure if the A10 has some internal
RAM where you can download the blink program and run it from there.

4. It is possible the fex file can be told to directly run the blink
program by loading it from the tf card. After all, something must tell
the A10 to boot uboot from tf card!

I'm sure someone can correct me on all of this!!
Its a good project for embedded students - and for everyone to have
these steps documented.

> 
> Everyone is talking about the criticality of DDR layout, the PCBs of
> tablets also shows those length matched tracks. Is it only about
> terminating the fast signal to avoid reflections or something more
> than that in the case of DDR3. There are many references on the web,
> it looks like.
> http://alterawiki.com/wiki/File:Board_guidelines_ddr2_ddr3.pdf
> http://www.fedevel.com/welldoneblog/2011/02/ddr-ddr2-ddr3-pcb-layout-examples/  
> 
> ajith

I agree Ajith there is a lot of R&D and knowledge out there
about reflections and PCB design. Please do continue to tell me I'm
wrong and why - because all these links enriches us all. My only defence
is that it doesn't agree with my experiences. Its a chance to check up
on all the theory and if I'm wrong, I'll admit to it, explain what went
wrong and redo the PCBs. I have budget for several iterations, so I'm
not desperate to get it right first time, second time etc.