VCL component for reading UID from ACS / ACR contactless readers on Windows

It talks to the Windows Smart Card API (winscard.dll / PC/SC).

UID is requested with the PC/SC Escape APDU used by ACS readers:

FF CA 00 00 Le

Le is 04 for 4-byte UIDs and 07 for 7-byte UIDs.

ComponentTDFACSReaderPaletteDF ACSPlatformsVCL Win32 / Win64Websitedelphifan.comEmail[email protected]

Requirements

• Delphi 10.3 Rio or later

• Windows Smart Card service running

• ACS / ACR (or other PC/SC) reader driver installed

• Reader plugged in

Folder layout

Delphi/
  Source/
    DFWinSCard.pas          WinSCard API
    DFACSReader.pas         TDFACSReader
    DFACSReaderReg.pas      palette registration
    DFACSReader.dpk         optional runtime package
    dclDFACSReader.dpk      design-time package (Install)
  Demo/
    DFACSReaderDemo.dpr     VCL demo
    uMain.pas / uMain.dfm
  DFACSReader.groupproj
  README.md

Install on the Tool Palette

The component appears next to other VCL controls only after the design-time package is installed.

1. Open Source\dclDFACSReader.dpk in Delphi.

2. Right-click the package → Install.

3. Open a VCL form.

4. Open the Tool Palette and find the DF ACS category, or search for DFACSReader.

5. Drop TDFACSReader on the form.

If the category is missing: Component → Install Packages, confirm dclDFACSReader is checked.

Installing the demo project from source does not register the palette item. Palette registration comes only from Install.

Quick start

procedure TForm1.FormCreate(Sender: TObject);
begin
  ACSReader.LoadReaders(cbxReaders.Items, True);
  ACSReader.ReadingMode := rmUID4Hex;
  ACSReader.Active := True;
end;

procedure TForm1.ACSReaderUIDRead(Sender: TObject; const UID: string);
begin
  EditUID.Text := UID;
end;

Typical flow:

1. Call LoadReaders (or set ReaderName yourself).

2. Set ReadingMode.

3. Assign OnUIDRead.

4. Set Active := True (or call Start).

5. Present a card. The component raises OnCardInserted, then reads the UID and raises OnUIDRead.

Properties

PropertyTypeDefaultDescriptionActiveBooleanFalseStarts / stops card insert monitoring. Safe at design time (no PC/SC I/O).ReaderNamestring''PC/SC reader name, e.g. ACS ACR122 0. Changing it while active restarts the monitor.ReadingModeTDFACSReadingModermUID4HexUID format (see table below).DuplicateBlockMsInteger400Ignore the same UID if it is reported again within this many milliseconds. 0 disables.

Methods

MethodDescriptionGetReadersReturns connected PC/SC reader names.LoadReaders(Dest, SelectFirst)Fills a TStrings / combo. If SelectFirst is true, sets ReaderName to the first reader.ReadUIDReads UID now from ReaderName using ReadingMode. Card must already be on the reader.ReadUID(ReaderName, Mode)Same, with explicit reader and mode.Start / StopSame as Active := True / False.

Events

EventWhenOnUIDReadUID was read after a card insert (duplicate filter applied).OnCardInsertedCard present after empty (before UID read).OnCardRemovedCard taken off the reader.OnErrorPC/SC or APDU error. Code is the raw LONG status.OnStartedMonitor thread started.OnStoppedMonitor stopped.

OnUIDRead and the card events run on the main thread.

Reading modes

Compatible with the original VB.NET UIDtoKeyboard modes 1–6.

EnumVB modeOutputrmUID4Hex14-byte UID, hex, as reported (A1B2C3D4)rmUID4HexReversed24-byte UID, hex, byte-reversedrmUID7Hex37-byte UID, hexrmUID7HexReversed47-byte UID, hex, byte-reversedrmUID4DecReversed5first 4 bytes reversed, then unsigned 32-bit decimalrmUID4Dec6first 4 bytes as little-endian UInt32 decimal

Hex strings are uppercase, no separators.

Demo

Open Demo\DFACSReaderDemo.dpr.

• Yenile — refresh reader list

• Reading mode — modes 1–6

• Başlat / Durdur — start / stop monitoring

• Bir kez oku — read UID immediately

You can compile the demo without installing the package; the demo links DFACSReader.pas directly.

Using in your own project

With palette (recommended)

1. Install dclDFACSReader.dpk.

2. Drop TDFACSReader on a form.

3. Wire events in the Object Inspector.

Without palette

Add these units to the project:

• Source\DFWinSCard.pas

• Source\DFACSReader.pas

Create the component in code:

ACSReader := TDFACSReader.Create(Self);
ACSReader.OnUIDRead := ACSReaderUIDRead;
ACSReader.LoadReaders(cbxReaders.Items, True);
ACSReader.Active := True;

Runtime package (optional)

DFACSReader.dpk is a run-only package if you prefer linking against a BPL instead of compiling the units into each EXE. Most VCL apps can ignore it and compile the units statically.

How it works

1. SCardEstablishContext / SCardListReadersW — enumerate readers

2. Background SCardGetStatusChangeW — wait for card insert / remove

3. SCardConnectW + SCardTransmit — send FF CA 00 00 Le

4. Status words 90 00 — UID bytes are everything before SW1/SW2

The old .NET libraries only wrapped this same Windows API. This component calls winscard.dll from Delphi.

Troubleshooting

SymptomWhat to checkNo readersDriver installed, reader powered, Smart Card service (SCardSvr) running. Click refresh after plugging in.No smart card on ReadUIDCard is not on the antenna, or the card is not ISO 14443.APDU SW not 9000Reader/firmware may not support GET DATA UID, or the card needs a different Le.Component missing from paletteInstall dclDFACSReader.dpk. Search the palette for DFACSReader.Duplicate UID eventsIncrease DuplicateBlockMs.

Link :https://github.com/delphifanforum/DFAcsReader