Reading binary data from serial port using Dejan TComport Delphi component

Question

Apologies for this question but I am a bit of a noob with Delphi. I am using Dejan TComport component to get data from a serial port. A box of equipment connected to the port sends about 100 bytes of binary data to the serial port. What I want to do is extract the bytes as numerical values into an array so that I can perform calculations on them.

TComport has a method Read(buffer,Count) which reads DATA from input buffer.

function Read(var Buffer; Count: Integer): Integer;

The help says the Buffer variable must be large enough to hold Count bytes but does not provide any example of how to use this function. I can see that the Count variable holds the number of bytes received but I can't find a way to access the bytes in Buffer.

TComport also has a methord Readstr which reads data from input buffer into a STRING variable.

function ReadStr(var Str: String; Count: Integer): Integer;

Again the Count variable shows the number of bytes received and I can use Memo1.Text:=str to display some information but obviously Memo1 has problems displaying the control characters. I have tried various ways to try and extract the byte data from Str but so far without success.

I am sure it must be easy. Here's hoping.

Answer 1

@johnma, I recommend that you use the TurboPower Async Library, it is very efficient, has many examples and is well documented.

check these links

• Download http://sourceforge.net/projects/tpapro/
• Version for Delphi 2009 and 2010 http://www.songbeamer.com/delphi/
• Developer's Guide

Answer 2

In this function

function Read(var Buffer; Count: Integer): Integer;

The Count parameter is the number of bytes you expect to read. While the function return value is actually read bytes.

If you have a Buffer defined as an array of 100 bytes you can code

x := Read(Buffer, 100);

and if the input is only 70 bytes then x will be 70. That way you can read while x > 0

Answer 3

// I use a timer to read a weight coming in on the Serial Port
// but the routing could also be triggered by OnRXChar (received data event)
// or OnRXBufferFull event.

var
  WeightString: String; //global

procedure TfmUDF.tmScaleTimer(Sender: TObject);
var
  Data: AnsiString;
begin
  ReadStr(Data,Count); //the individual bytes can be read Data[n].....
  WeightData:=WeightData+Data; //just keeps adding the incoming data
end;

Does this help?

Answer 4

Hi there - sorry to re-open this thread, but I might be having a similar problem...

I'm trying to replicate an old Windows program running in XP that reads data from an old valve machine via RS232.

I am using unchanged ComExample.dpr, with rxOnChar, but only first 2 chars show on memo i.e. ",," which (I believe) is the first packet.

Has anyone any idea as to why?

e.g. ComSpy shows data as follows: ",, ÿ B 101SV30 0898 mˆ‚PPš" etc. etc.
(but all I get is these first 2 characters which ComSpy identifies as first packet)

Very many thanks in advance

Paul.

P.S. Additional Comspy info is as follows:

In/out queue size 1024/512
Purge the serial port: RXABORT, RXCLEAR, TXABORT, TXCLEAR
Set timeouts: ReadInterval=-1, ReadTotalTimeoutMultiplier=0, ReadTotalTimeoutConstant=0, WriteTotalTimeoutMultiplier=0, WriteTotalTimeoutConstant=5000 Baud rate 9600 (I've set this)
RTS off
DTR on
Data bits=8, Stop bits=1, Parity=Odd (and I've set these)
Set chars: Eof=0x1A, Error=0x3F, Break=0x3F, Event=0x00, Xon=0x11, Xoff=0x13
Handflow: ControlHandShake=(DTR_CONTROL), FlowReplace=(ERROR_CHAR), XonLimit=256, XoffLimit=256