Thank you MouettE for your advice. I tried it with and without seriel connection, with and without lan cable, using the upper and the lower usb port. The thumb drive I use has a fresh msdos partition table with a single vfat partiton on it. However, the u-boot on the nor flash stays at 2010.06. The series output starts like this.
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U-Boot 2010.06 (Jun 10 2011 - 09:06:51)
BUBBA|3
SoC: Kirkwood 88F6281_A0
DRAM: 512 MiB
In: serial
Out: serial
Err: serial
Net: egiga0, egiga1
88E1116 Initializing on egiga0 @08 done
88E1116 Initializing on egiga1 @18 done
Hit any key to stop autoboot: 0
** Bad partition 1 **
Wrong Image Format for bootm command
ERROR: can't get kernel image!
resetting ...
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I also tried to flash u-boot from the u-boot command line using "sf erase" und "sf write" but nothing could change the content of the flash. Might there be a jumper I have to set? In case the nor flash is damaged, is it possible to replace it?
I want to use the community u-boot from github [1] which you might know, since the last commit if from you.
Btw. what is the difference between this repo and your own [2] despite the fact that [2] look more official.
Thanks!
[1]
https://github.com/nielsek/community-b3-uboot
[2]
https://github.com/Excito/U-Boot-B3