[U-Boot-Users] Re: Installing U-Boot on target via USB/serial using U-Boot commands

[Jerry Van Baren]

Disclaimer: I'm not an ARM expert.  I have a hard time even spelling ARM.

Joe Grisso wrote:
> See below.
> 
> 
>>It looks like this is a very simple loader.  It writes to SRAM _only_
>>and then jumps to that program (JTAG loaders typically allow you to
>>write to flash, manipulate registers, and jump anywhere, single step,
>>etc.).  Theoretically you could load u-boot this way, but nobody has
>>volunteered that they have done it so you would likely be blazing a new
>>path.
> 
> 
> Yeah, and with only 16KB of onboard SRAM, I doubt you'd be able to load
> U-Boot in as a single image. I don't know if Atmel's host-side DFU app
> handles downloads larger than the size of SRAM either. So if not, one
> would have to write an app for that on the host as well.

Nope.  U-boot is much more than 16K.  The level of complexity just 
stepped up a notch.

Looking some more at the description, the USB load is done only if no 
"valid" load (the vectors have jump instructions in them) is found in a 
bootable memory.  This means that you would only get one chance to burn 
the vectors - if your load in regular boot memory does not run properly, 
the bootloader doesn't know to go back to USB boot and your hardware 
will turn into a brick (recoverable only with a JTAG loader).

You need a JTAG loader/debugger.  The USB mechanism would work for a low 
budget loader once you have a working program to load, but using the USB 
mechanism to load your initial boot loader will be a one shot failure.

>>Having said all that, this is pretty much off topic for u-boot.  Only
>>after you get u-boot loaded into the target (and at least showing some
>>signs of life) would this become on topic for this list.
> 
> 
> Just out of curiosity, which list would be appropriate then? AT91 Users?

Sorry, I'm just an "idea" man :-/ lots of ideas, very little practice.

> Best Regards,
> 
> Joe Grisso
> Detachment 3 Media, Ltd.

gvb