<div dir="ltr">The debugger should be breaking (as in break-point) on the line causing the AV. Tell us where that is and we may be able to help.<br><br>I would also suggest that you greatly simplify the code you are using to work with the buffers being passed to and received from the API. The more steps you introduce to achieve something, the greater chance that one of those steps will introduce an inadvertent error (and make it harder to identify where that error is creeping in.<br><br>For example, if the API requires a pointer to a null terminated key value of 6 $FF bytes then simply declare a constant and pass the address of that, rather than building a string. Apart from anything else, depending on which version of Delphi you are using, your technique of using an intermediate "String" may yield a PANSIChar (char = byte-size) or PWIDEChar (char = word-size) and one of these is almost certainly not what the API you are using is expecting.<br><br>And note that even if this technique works in a version of Delphi where String = ANSI, it will likely break when you upgrade and recompile in a version where String = UTF16.<br><br>Using a constant you not only eliminate a whole chunk of unnecessary code but can be entirely explicit in what you are trying to achieve, so for a byte buffer:<br><br> const<div> KEY = array[0..6] of Byte = ($FF,$FF,$FF,$FF,$FF,$FF,$00);<br><br><span style="font-size:12.8000001907349px"> receive:=API_PCDRead(0,0,$00,</span><span style="font-size:12.8000001907349px">10,1,@KEY,bufferr); </span><br><br></div><div><br></div><div>This might even be the cause of your problem.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On 28 May 2015 at 00:14, Robo <span dir="ltr"><<a href="mailto:robo555@gmail.com" target="_blank">robo555@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Are you able to debug which line of code the error is occuring on?<br></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Wed, May 27, 2015 at 1:56 PM, Marshland Engineering <span dir="ltr"><<a href="mailto:marshland@marshland.co.nz" target="_blank">marshland@marshland.co.nz</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I'm a bit out my depth. Is there something I have missed ?<br>
<br>
EAccess violation at address 000000000<br>
<br>
I purchased an RFID reader with sample code. I stripped out what was not<br>
necessary and ended up with this.<br>
<br>
Sorry for the long code<br>
<br>
**************************************************************<br>
<br>
unit Unit1;<br>
<br>
interface<br>
<br>
uses<br>
Windows, Messages, SysUtils, Variants, Classes, Controls, Forms,<br>
ComCtrls, StdCtrls, XPMenu, ExtCtrls;<br>
<br>
type<br>
TForm1 = class(TForm)<br>
showm: TRichEdit;<br>
Button1: TButton;<br>
procedure falsereason(s:string);<br>
procedure bReadClick(Sender: TObject);<br>
private<br>
{ Private declarations }<br>
public<br>
{ Public declarations }<br>
end;<br>
<br>
function<br>
API_PCDRead(comHandle:Thandle;DeviceAddress:integer;mode:byte;add_blk,num_blk:integer;<br>
snr,buffer:pchar):integer;stdcall;external 'mi.dll';<br>
<br>
var<br>
Form1: TForm1;<br>
comhandle : Thandle ;<br>
reason:string;<br>
implementation<br>
<br>
{$R *.dfm}<br>
<br>
procedure TForm1.falsereason(s:string);<br>
begin<br>
if s='' then begin reason:=''; exit; end;<br>
if s='00' then begin reason:=''; exit ; end;<br>
etc<br>
if s='96' then begin reason:='The Operation Do Not Success....'; exit;<br>
end;<br>
end;<br>
<br>
procedure TForm1.bReadClick(Sender: TObject);<br>
var<br>
buffer,bufferr:array [0..255] of char;<br>
receive,i :integer;<br>
keydata,cardnum,showmemo:string;<br>
key : pchar;<br>
begin<br>
setlength(keydata,6);<br>
for i:=1 to 6 do begin<br>
keydata[i]:=Chr(StrToInt('$FF'));<br>
end;<br>
key:=StrPCopy(buffer,keydata);<br>
receive:=API_PCDRead(0,0,$00,10,1,key,bufferr);<br>
case receive of<br>
0:begin<br>
for i:=0 to 3 do begin<br>
cardnum:=cardnum+ inttohex(ord(buffer[i]),2);<br>
end;<br>
showm.Lines.Add('Number :'+cardnum);<br>
end;<br>
1:begin<br>
falsereason(inttohex(ord(bufferr[0]),2));<br>
showm.Lines.Add(reason+#13#10);<br>
end<br>
else<br>
showm.Lines.Add('error,no data receive...'+#13#10);<br>
end;<br>
end;<br>
<br>
end.<br>
****************************************************************<br>
I added the above to my code and it complies but crashes when I do a receive.<br>
EAccess<br>
<br>
<br>
unit uMain;<br>
<br>
interface<br>
<br>
uses<br>
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,<br>
Dialogs, Grids, DBGrids, Menus, ComCtrls, StdCtrls, Printers, DBCtrls,<br>
Mask, ExtCtrls, IniFiles, DB, ShellAPI, XPMenu;<br>
<br>
<br>
type<br>
TfMain = class(TForm)<br>
pcMembers: TPageControl;<br>
Members: TTabSheet;<br>
Events: TTabSheet;<br>
DBGrid1: TDBGrid;<br>
DBGrid4: TDBGrid;<br>
DBGrid5: TDBGrid;<br>
Label3: TLabel;<br>
bFees: TButton;<br>
Button1: TButton;<br>
bEmail: TButton;<br>
dbgMembers: TDBGrid;<br>
Label5: TLabel;<br>
Label7: TLabel;<br>
dbgFeesMem: TDBGrid;<br>
dbgSubs: TDBGrid;<br>
Label4: TLabel;<br>
Label2: TLabel;<br>
puSubs: TPopupMenu;<br>
puSubsAdd: TMenuItem;<br>
puSubsDel: TMenuItem;<br>
puFeesListPrinter: TMenuItem;<br>
puFeesListScreen: TMenuItem;<br>
upFeesCardsNotSent: TMenuItem;<br>
PrintSet1: TPrinterSetupDialog;<br>
puEventFees: TPopupMenu;<br>
puFeesAdd: TMenuItem;<br>
puFeesDelete: TMenuItem;<br>
puFeesList: TMenuItem;<br>
puMembers: TPopupMenu;<br>
puAddMember: TMenuItem;<br>
puDeleteMember: TMenuItem;<br>
puBikes: TPopupMenu;<br>
puAddBike: TMenuItem;<br>
puDeleteBike: TMenuItem;<br>
dbmNotes: TDBMemo;<br>
Label6: TLabel;<br>
dbgIncident: TDBGrid;<br>
Label8: TLabel;<br>
PrintDialog1: TPrintDialog;<br>
puIncident: TPopupMenu;<br>
AddIncident1: TMenuItem;<br>
DeleteIncident1: TMenuItem;<br>
dtpMainDate: TDateTimePicker;<br>
DBEdit1: TDBEdit;<br>
Label1: TLabel;<br>
Label9: TLabel;<br>
cbMainYear: TComboBox;<br>
DBGrid2: TDBGrid;<br>
bPostFees: TButton;<br>
Button2: TButton;<br>
eCardNumber: TEdit;<br>
procedure dbgMembersDblClick(Sender: TObject);<br>
procedure FormCreate(Sender: TObject);<br>
procedure dbgSubsDblClick(Sender: TObject);<br>
procedure puSubsAddClick(Sender: TObject);<br>
procedure puSubsDelClick(Sender: TObject);<br>
procedure upFeesCardsNotSentClick(Sender: TObject);<br>
procedure puFeesListPrinterClick(Sender: TObject);<br>
procedure FormShow(Sender: TObject);<br>
procedure dbmNotesExit(Sender: TObject);<br>
procedure puFeesAddClick(Sender: TObject);<br>
procedure puFeesDeleteClick(Sender: TObject);<br>
procedure dbgFeesDblClick(Sender: TObject);<br>
procedure dbgMembersKeyPress(Sender: TObject; var Key: Char);<br>
procedure puFeesListClick(Sender: TObject);<br>
procedure Button1Click(Sender: TObject);<br>
procedure puAddMemberClick(Sender: TObject);<br>
procedure puDeleteMemberClick(Sender: TObject);<br>
procedure puAddBikeClick(Sender: TObject);<br>
procedure puDeleteBikeClick(Sender: TObject);<br>
procedure DBGrid2DblClick(Sender: TObject);<br>
procedure dbmNotesEnter(Sender: TObject);<br>
procedure puFeesListScreenClick(Sender: TObject);<br>
procedure bEmailClick(Sender: TObject);<br>
procedure DBGrid3ColExit(Sender: TObject);<br>
procedure dbgIncidentCellClick(Column: TColumn);<br>
procedure AddIncident1Click(Sender: TObject);<br>
procedure DeleteIncident1Click(Sender: TObject);<br>
procedure MembersShow(Sender: TObject);<br>
procedure Button2Click(Sender: TObject);<br>
procedure falsereason(s:string);<br>
private<br>
{ Private declarations }<br>
public<br>
sKey:String;<br>
bFeesFirstTime:Boolean;<br>
end;<br>
<br>
function<br>
API_PCDRead(comHandle:Thandle;DeviceAddress:integer;mode:byte;add_blk,num_blk:integer;<br>
snr,buffer:pchar):integer;stdcall;external 'mi.dll';<br>
<br>
var<br>
fMain:TfMain;<br>
comhandle:Thandle ;<br>
Reason:String;<br>
<br>
implementation<br>
<br>
uses uDM, uMembers, uSubs, uMemCards, uEventFees, uLogon, uBikes, uMemoShow,<br>
uEmail, uIncident;<br>
<br>
{$R *.dfm}<br>
<br>
procedure TfMain.falsereason(s:string);<br>
begin<br>
if s='' then begin reason:=''; exit; end;<br>
if s='00' then begin reason:=''; exit ; end;<br>
etc<br>
if s='95' then begin reason:='The lock Operation Do Not Success....';<br>
exit; end;<br>
if s='96' then begin reason:='The Operation Do Not Success....'; exit;<br>
end;<br>
end;<br>
<br>
<br>
******** My other code,<br>
<br>
procedure TfMain.Button2Click(Sender: TObject);<br>
var<br>
buffer,bufferr:array [0..255] of char;<br>
receive,i :integer;<br>
keydata,cardnum,showmemo:string;<br>
key : pchar;<br>
begin<br>
setlength(keydata,6);<br>
for i:=1 to 6 do begin<br>
keydata[i]:=Chr(StrToInt('$FF'));<br>
end;<br>
key:=StrPCopy(buffer,keydata);<br>
receive:=API_PCDRead(0,0,$00,10,1,key,bufferr);<br>
case receive of<br>
0:begin<br>
for i:=0 to 3 do begin<br>
cardnum:=cardnum+ inttohex(ord(buffer[i]),2);<br>
end;<br>
showm.Lines.Add('Number :'+cardnum);<br>
end;<br>
1:begin<br>
falsereason(inttohex(ord(bufferr[0]),2));<br>
showm.Lines.Add(reason+#13#10);<br>
end<br>
else<br>
showm.Lines.Add('error,no data receive...'+#13#10);<br>
end;<br>
end;<br>
<br>
end.<br>
<br>
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</blockquote></div><br></div>
</div></div><br>_______________________________________________<br>
NZ Borland Developers Group - Delphi mailing list<br>
Post: <a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><br>
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