I'm success compiling u-boot, but on the tutorial (http://www.udoo.org/docs/Advanced_Topics/Compile_U-Boot_Bootloader.html) part of flash to sd card : sudo dd if=SPL of=/dev/mmcblk0 bs=1K seek=1 sudo dd if=u-boot.img of=/dev/mmcblk0 bs=1K seek=69 My host pc use Linux mint, i'm only find sdx, which one sdc or sd1 to replace mmcblk0 I was tryed to flash sdc and sdc1, after that udoo cant start..
In your case you need to use /dev/sdc - not sdc1. sdc1 indicates first partititon. Be sure that this is your sd card!