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.

#!/bin/sh
set -ex
rm -rf binutils-2.21.1
rm -rf binutils-build
rm -rf gcc-4.5.4
rm -rf gcc-build
rm -rf newlib-2.0.0
rm -rf newlib-build