asked on

How to check the previous value of variable

Hello Experts,
My situation is:
I receive data from rs232 using ComPort in Delphi, I receive it every single secound becouse the transfer of data from RS232 has some errors I`m forced to check the value of 2 variables - one value which has been just transfered and secound value which has been transfered one sec. earlier. I want to do this becouse I`m going to compare these two values and if the difference would be grater then let`s say 100 i won`t save the data to database.
Here is the code which I use to receive and save data from ComPort.
procedure TForm10.ComDataPacket5Packet(Sender: TObject; const Str: string);
var
m1,w1:Double;
Str2,Str3,w,m,rap : String;
begin
ComDataPacket5.Size:=0;
ComDataPacket5.StartString:=#02;
ComDataPacket5.StopString:=#13;
rap:= FormatDateTime('yyyy-MM-dd',Now)+' '+FormatDateTime('HH:mm:ss',Now);
Str2 := Copy(Str,4,13);
m:=Trim(Str2);
m1:=ConvertFloat(m);
Str3:=Copy(Str,14,26);
w:=Trim(Str3);
w1:=ConvertFloat(w);
if (Pos('.', FloatToStr(m1)) <= 5) and (Pos('.', FloatToStr(m1)) > 0 ) then
begin
with Form1.ADOQuery2, SQL do
begin
Close;
Clear;
Add('INSERT INTO PRODUKCJA (WAGA,MASA,RATE,DATA,CZAS,RAPORT) VALUES (''6,3-12,8'',:masa,:rate,CONVERT(CHAR(10),GETDATE(),120),CONVERT(CHAR(8),GETDATE(),108),:raport)');
Parameters.ParamByName('masa').Value := m1;
Parameters.ParamByName('rate').Value := w1;
Parameters.ParamByName('raport').Value := rap;
ExecSQL;
end;
Form1.Edit6.Text := FloatToStr(m1);
Form1.Edit14.Text:=FloatToStr(w1);
Form1.Chart1.Series[4].AddXY(Time,m1);
end;
end;

Please Experts Pimp my app :))

MerijnB

You have to give a little more details:

- what do all the vars mean in your code (m1, w1, Str2, Str3, w, m rap)
- what kind of data are you receiving (what format)
- what do you want to check?

Vaalar

ASKER

Hello Merlijn
1. Vars:
m:=Trim(Str2); - just to del white spaces
m1:=ConvertFloat(m); - conversion from str to float
the same situation with w and w1
as you can see I`m converting received string from ComPort
Str2 := Copy(Str,4,13); - var for the part of data from ComPort

2. It`s an ascii string
ComDataPacket5.StartString:=#02;<- start sign for package
ComDataPacket5.StopString:=#13;<- stop sign for package
3. I want to check what value had the m1 var and compare it with next value of m1
I give you an example:
at 12:01:23 i have got the m1 with value = 121.812
at 12:01:24 I have got the m1 with value = 1211
now i want to compare the m1 value at 12:01:24 and the value at 12:01:23 and if the difference would be greater than 100 i know that the value at 12:01:24 is wrong.
BR
Vaalar

Vaalar

ASKER

The Lenght of string from ComDataPacket is always 26 chars long. I can divide it and in first part i receive weight and in secound rate. That`a why i`m using Str2( chars from 4 to 13 ) and Str3 ( chars from 14 to 26 ). Rap is value for Rave Report so it`s not connected.
BR
Vaalar

ASKER CERTIFIED SOLUTION

Geert G

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

Vaalar

ASKER

Hello Gert,
I have one request, Can you make some description where should i put the code and what is the purpose of using it. Sry for this but I would like to know what I`m doing and why.
Thx again
Vaalar

Geert G

no problem

type
// this record will be used to store the last data
RLastData = record
M1_Last: Double; // Last value for M1
M1_Prior: Double; // Next to last value for M1
W1_Last: Double; // Last value for W1
W1_Prior: Double; // Next to last value for W1
end;

TForm10 = class(TForm)
procedure FormCreate(Sender: TObject);
private
// record variable for storing last data
fPort5Data: RLastData;
// initialisation routine
procedure InitPortData(var aPortData: RLastData);
// save last data in record variable
procedure SavePortData(var aPortData: RLastData; M1, W1: Double);

end;

procedure TForm10.FormCreate(Sender: TObject);
begin
//Initialise record variables
InitPortData(fPort5Data);
end;

procedure TForm10.InitPortData(var aPortData: RLastData);
begin
with aPortData do
begin
M1_Last := 0;
M1_Prior := 0;
W1_Last := -1;
W1_Prior := -1;
end;
end;

procedure TForm10.SavePortData(var aPortData: RLastData; M1, W1: Double);
begin
// Move the data to the next to last data
W1_Prior := W1_Last;
M1_Prior := M1_Last;

// Save the current values in the last data
W1_Last := W1;
M1_Last := M1;
end;

you need to initialise the record variables in the FormCreate as this is not done automatically
do this for all the port record variables you define

if W1_Prior = -1 then there is no 2 values yet
you can only check as from the 3rd value

the purpose of using it ?
i based myself on your question ...
you needed the previous data and the data before that of 2 variables
this is one way of doing it

Vaalar

ASKER

Geert you are really a piece of Expert :)
Thx for all.
Points granted.
and the last question:
should i put your code in this place:

procedure FormCreate(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure FormDestroy(Sender: TObject);
private
fPort5Data: RLastData;
procedure InitPortData(var aPortData: RLastData);
procedure SavePortData(var aPortData: RLastData; M1, W1: Double);
public
{ Public declarations }
end;

var
Form10: TForm10;
type
RLastData = record
M1_Last: Double;
M1_Prior: Double;
W1_Last: Double;
W1_Prior: Double;
end;

Thx again
BR
Vaalar

Vaalar

ASKER

Thx for your professional help

Vaalar

ASKER

I have made it this way:
procedure FormCreate(Sender: TObject);
type
RLastData = record
M1_Last: Double;
M1_Prior: Double;
W1_Last: Double;
W1_Prior: Double;
end;
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure FormDestroy(Sender: TObject);
private
fPort5Data: RLastData;
procedure InitPortData(var aPortData: RLastData);
procedure SavePortData(var aPortData: RLastData; M1, W1: Double);
public
{ Public declarations }
end;

but I`ve got such error:
[DCC Error] RS232_MAIN.pas(76): E2003 Undeclared identifier: 'W1_Prior'
[DCC Error] RS232_MAIN.pas(76): E2003 Undeclared identifier: 'W1_Last'
[DCC Error] RS232_MAIN.pas(78): E2003 Undeclared identifier: 'M1_Prior'
[DCC Error] RS232_MAIN.pas(78): E2003 Undeclared identifier: 'M1_Last'
What I`ve made wrong

Geert G

hmmm, no won't work

RLastData is a type definition

so is TForm10

there are sections for declarations of type

unit Test;

interface

use unit1, unit2, unit3, etc.

const
// declare const here
A = 1;
B = 2;

type
// declare type definitions here
// record definitions
RLastData = record end;

// procedural type definitions
TNotifyEvent = procedure (Sender: TObject) of object;

// class / form type definitions
TForm1 = class(TForm) end;

// declare variables here
var
VarA: Integer;
varB: Int64;

implementation

the type definition of TForm10 has a procedure which uses the type definition RLastData
so you need to put the record type definition of RLastData before the type definition of TForm10
it's a definition of what data a variable will hold, not the actual variable itself !

you can manually alter anything in the private,protected and public sections of the TForm10
but don't change anything manually between
TForm10 = class(TForm)
and // leave this to the Delphi IDE to change
private