2 Visual Components Manuals

Introduction to Visual Components 2.3
4.10.7.1.3 3. Creating the User Task for Key Matrix Operation
The task must be created in the task class where key matrix handling also takes place. It is easiest to have key
matrix acquisition retrieval and evaluation in the same task. In this way, the logic in the application always works
with the most current key data and the highest possible performance can be achieved. 50 milliseconds is a
recommendable task cycle time for key matrix operation.
The following examples illustrate how such a task could look in the Automation Basic and ANSI C programming
languages. These examples can be adapted to specific application needs.
4.10.7.1.3.1 3.1 Automation Basic
4.10.7.1.3.1.1 Init subprogram
(* init program *)
step = 0
erase = 1
4.10.7.1.3.1.2 Cyclic program
(* cyclic program *)
(* get handle for project "vga1" *)
IF step = 0 THEN
VC_HANDLE := VA_Setup(1, "vga1")
IF VC_HANDLE 0 THEN
step := 1
ENDIF
ENDIF
(* try to read the current key matrix *)
IF step = 1 THEN
status := VA_GetKeyMatrix(1, VC_HANDLE, ADR(mtxKeys), 48, ADR(mtxSize))
IF status 0 THEN
(* could not read matrix *)
erase = 1
(* handle project overload, handle becomes invalid *)
IF status = 100 THEN
step := 0
ENDIF
ENDIF
ENDIF
(* erase the key matrix in case of error *)
IF erase = 1 THEN
LOOP i := 0 TO 47 DO
mtxKeys[i] = 0
ENDLOOP
erase := 0
ENDIF
(* your key handling code goes here *)
4.10.7.1.3.1.3 Declaration
An array of USINT variables must be created using an appropriate length for the key matrix stored in the
'mtxKeys' variable. If another length should be used, the VA_GetKeyMatrix function call must be adjusted
4.10.7.1 Using the Key Matrix 395