The USB Updater image is officially headless, meaning it's not designed to make any use of a display, whether external or internal. Recently one downstream developer created a novel modification to this paradigm and suggested we should share it with the community:
Using openvt, you can add text output to the LCD panel on the TPC product. This would be added to the blast.sh script thus:
openvt -c 1 my_blast.sh
This will allow stdout and stderr to be output to the LCD screen.
Going one step further, it is a good idea to disable the Linux automatic backlight-off feature thus:
echo -ne '\033[9;0]' > /dev/tty1
If turning off the backlight is desireable (for example in a battery-operated environment), changing the 0 in [9;0] to some other number will enable the screen-saver function, disabling the backlight after the number of seconds specified.