Correctly handle structured variables that include FB and external FBs (example: FB1.FB2.extFB3.FB4.extFB5.extFB6.structvar.field1 := 42;) (this commit fixes only ST code. TODO: IL and SFC)
FUNCTION_BLOCK DERIVATIVE
VAR_INPUT
RUN : BOOL ; (* 0 = reset *)
XIN : REAL ; (* Input to be differentiated *)
CYCLE : TIME ; (* Sampling period *)
END_VAR
VAR_OUTPUT
XOUT : REAL ; (* Differentiated output *)
END_VAR
VAR X1, X2, X3 : REAL ; END_VAR
IF RUN THEN
XOUT := (3.0 * (XIN - X3) + X1 - X2)
/ (10.0 * TIME_TO_REAL(CYCLE)) ;
X3 := X2 ; X2 := X1 ; X1 := XIN ;
ELSE XOUT := 0.0; X1 := XIN ; X2 := XIN ; X3 := XIN ;
END_IF ;
END_FUNCTION_BLOCK