setenv is a part of uboot , so if you can use any linux command then you are not in uboot . Connect to the micro usb socket cn6 , power on and you should see ... 4 - 3 - 2 - 1 , press any key before that 4 second or it will start to boot. Now you are in uboot !!!!
Here to connect UDOO via serial cable: http://www.udoo.org/ProjectsAndTutorial ... lioID=1394 here to set the environment variables once you're in uboot: http://www.udoo.org/faq-items/how-do-i-set-up-my-lvds/