HEKA EPC 9 - Sample Program

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Controlling E9Screen EPC9 Installation 93

Sample program

The listing below is an excerpt from the program used to test the E9Screen

communication protocol. It demonstrates the functions needed to write an own program

to control the EPC9 through the E9Screen program. The code is written in Modula-2. The

code can be easily understood also by readers familiar with BASIC, PASCAL, C, C++, or

FORTRAN.

MODULE UserCommands;

CONST

CommandName = 'EPC9In.EPC';

MessageName = 'EPC9Out.EPC';

VAR

CommandFile : IOFiles.FileHandleType;

MessageFile : IOFiles.FileHandleType;

Signature : INTEGER;

LastSignature : INTEGER;

PROCEDURE WriteError( Text : ARRAY OF CHAR );

VAR

Work : ARRAY[0..79] OF CHAR;

BEGIN

IOFiles.Message( IOFiles.GetError(), Work );

TermIO.WriteString( Text );

TermIO.WriteString( ' failed: ' );

TermIO.WriteLine( Work );

Alert.Beep;

END WriteError;

PROCEDURE WriteToCommandFile( Text : ARRAY OF CHAR ): BOOLEAN;

VAR

Work : ARRAY[0..79] OF CHAR;

Count : INTEGER;

BEGIN

IF NOT CommandFile.IsOpen THEN RETURN FALSE; END;

IF Text[0] = 0C THEN RETURN TRUE; END;

Work[0] := 0C;

Decode.Integer( - ABS( Signature ), Work, 0 );

Count := Strings.Length( Work );

(* First, we write a negative signature to the first text line.

This prevents to the target E9Screen to read and interpret

the content of this file. We use the actual signature already

now, so that we can just change the sign from negative to

positive by overwriting one character!