Output from xvtouch looks like this on my box (with TCL 5.4):
open /dev/input/touchscreen
Device /dev/input/touchscreen = Hampshire Company TSHARC Analog Resistive
Input device ID: bus 0x3 vendor 0x7dd product 0x1 version 0x101
XOpenDisplay(':0')
calib(X,Y) (4038,4023)min (101,207)max
Screen 640x480
select: Resource temporarily unavailable
It repeats this over and over, approx. every 5 seconds.
I'm giving up on this path for now. Trying Xorg with xinput-calibrator.