AT command interface works! The cause of the breakage was the same Nucleus API issue with NU_Create_Timer() which we encountered at the very beginning of this project with Riviera timers: the code in uartfax.c from TCS211 was passing 0 as the initial dummy value for the timer duration, and our FreeNucleus version doesn't like it. The fix is the same: pass 1 as the initial dummy value instead.

if [ "$RVM_ETM_SWE" != 1 ]
then
	echo "Error: feature tmffs2: need feature etm first" 1>&2
	exit 1
fi

TMFFS2=1
export_to_c	TMFFS2