Entering usbboot through U+POWERON

Xiangfu Liu xiangfu at qi-hardware.com
Thu Dec 17 09:43:21 EST 2009

Bas Wijnen wrote:
> On Wed, Dec 16, 2009 at 03:16:12PM +0100, Kristoffer Ericson wrote:
>> On lars suggestion I increased the timeout to first 200, then 1000 and still getting
>> same issue. Could it be that my bootloader is too old for some reason? I mean
>> it obviously enters usbboot mode with U+POWERON but did you have earlier versions
>> of the bootloader that had that but still didnt work?
> No, that is not possible.  The boot loader that is used during usbboot
> is the boot rom inside the jz4740 (not in the flash rom, but really
> inside the cpu chip).  This is a very small program which lets the chip
> work as a usb device.  It accepts a few commands, which make it possible
> to boot the device over usb, even if the flash does not have a bootable
> image on it.

Hi Bas Wijnen
the [power] + [u] is run [1], not the inside rom.

> If things go wrong after running stage 1, as seems to be the case,
> several things can be wrong.  Most likely, the stage 1 code crashes for
> some reason, and the chip no longer responds to usb commands.  In some
> cases, it is possible to get meaningful output from the serial port.  If
> not, then I would add lots of output-producing commands to stage 1
> (starting after serial port setup), to see where it breaks.
> No delay at all should be required between running stage 1 and loading
> stage 2, because the usb device module is not touched yet.  Stage 2 will
> set up its own idea of the usb device, which will be different from the
> previous situation, so there you do need a delay.
> Thanks,
> Bas
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Xiangfu Liu
Email: xiangfu at qi-hardware dot com
Web: http://www.qi-hardware.com

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