If I initialize an LCD in my main program and try to write to it in a function, I get this
Compile... Failed! -------- compiler messages -------- Included libraries: simpletools single.c: In function 'DispLCD': single.c:54:13: error: 'debug_lcd' undeclared (first use in this function) single.c:54:13: note: each undeclared identifier is reported only once for each function it appears in