Building Linux kernel for A10, can't see boot sequence

[ozweepay]

I have an A10 board and using the pre-compiled image from https://www.olimex.com/wiki/A10-OLinuXino-LIME#Official_Images_from_OLIMEX the board boots up fine.  But oddly, the first thing I see is a Debian logo on a GUI desktop after about 20 seconds of waiting: there is no boot sequence shown prior to that.  Hitting various keys during boot-up doesn't seem to do anything.

My friend, who has this same board, has the same experience.  Is this normal?  Every other time I've used Linux in my career, the boot sequence was displayed before the desktop appeared.

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I attempted to rebuild the Linux kernel via instructions given at http://olimex.wordpress.com/2013/12/13/building-debian-linux-image-for-a10-olinuxino-lime-with-kernel-3-4-67/ which went fairly smoothly.  The only change I made was to turn on netfilter (so that iptables will work in the resulting Linux install).  However, after copying the resulting uImage to partition 1 on the SD card, my A10 card just hangs... and since there is no boot sequence displayed, I have little chance of debugging where things are going wrong.

Any advice on how to debug this?

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Here is the strangest thing: if I copy back the original uImage to the SD card, the A10 card still hangs.  Apparently something was disturbed during the attempted boot with the bad uImage.  I have to rewrite the entire 4MB image to get the card working again.

Any help GREATLY appreciated.

[ozweepay]

I'm replying to my own post here... 

Some digging around seems to imply that the boot sequence it emitted from the UART and to see it we need a converter (most likely) to USB 2.0 along with a driver.  See here: https://groups.google.com/forum/#!topic/linux-sunxi/Qb8a78CZ7N0

So I've ordered a cable.

[JohnS]

Typically there's a console=/dev/ttyS0 or the like passed to the kernel (which of course you can change) so a 3.3V level (not RS232 level) interface is good.

John

[MBR]

To display boot messages on VGA or LCD, the console kernel parameter must be changed to something like console=tty1,38400, so boot messages will go to active framebuffer. Be sure that the default kernel log level is set to some sane value and the quiet parameter is not used.

[ozweepay]

I purchased a cable from Amazon:
http://www.amazon.com/gp/product/B00C8KGRRA/
and overnight shipped it.  $10 total.

Connected white (Rx) to UART0 Tx, Green (Tx) to UART0 Rx, and Black to UART0 Ground.  Then installed the device driver from OLimex found here
https://www.olimex.com/Products/Components/Cables/USB-Serial-Cable/USB-Serial-Cable-F/

Used PuTTY with serial port set to COM10 (which the driver created) and 115200 baud, 8 bits, 1 stop, No parity.  Then powered up my A10.

This gave me the boot sequence.  Unforunately I can only SEE the output from the sequence... the keyboard of my Win box where PuTTY is running does not yield input to the OLinuXino board.

Hopefully all of this helps someone.