I cannot get a 'Velleman part No. VM116' to talk to my DMX lights

Question

Hello everybody.

First of all, I am using Delphi 7, the computer is connected to a 'Velleman part No. VM116' via a USB port and I have two DMX led lights connected to the DMX output of the controller.

I have placed the K8062d.dll library in the same folder as the executable, but I am not getting close to making the lights respond. The difficulty is that it should be as easy as pie, considering the trouble I had to get my 24 channel lighting desk to control my lights this controller should be just as easy as dropping a shape onto a form.

Anyway, here is the sample code...

unit chaser_control;

interface

type
  rgb=(
    c_red,
    c_green,
    c_blue);

  dmx_offset:array[rgb] of integer=(
    1,
    2,
    3);

  dmx_class=class(tobject)

    constructor create;
    destructor demolish;

    procedure initialise;
    procedure finish;

    procedure set_channel(
      can_dmx:integer;
      channel:rgb;
      c:integer);

  end;

var
  can:dmx_class;

implementation

// these four external procedures are all that is necessary to address and
// write to any of the 512 DMX channels in the chain

procedure StartDevice; stdcall; external 'K8062d.dll';
procedure SetData(Channel: Longint ; Data: Longint); stdcall; external 'K8062d.dll';
procedure SetChannelCount(Count: Longint); stdcall; external 'K8062d.dll';
procedure StopDevice; stdcall; external 'K8062d.dll';

  //
  // dmx control
  //

constructor dmx_class.create;
begin
  inherited;

  // the dmx controller is started once when this class is instantiated
  initialise;
end;

destructor dmx_class.demolish;
begin
  // the dmx controller is closed down when this class is destroyed
  finish;

  inherited;
end;

procedure dmx_class.initialise;
begin
  // call the device DLL
  StartDevice;

  // allocate 5 channels for led can [two channels are not used]
  SetChannelCount(5);

  // make sure that channel 1 is set to zero [i never use this channel, 
  // on the lighting desk it is set to zero]
  SetData(1,0);
end;

procedure dmx_class.finish;
begin
  // this procedure is called once

  StopDevice;
end;

  //
  // can control
  //

procedure dmx_class.set_channel(
  can_dmx:integer;
  channel:rgb;
  c:integer);
var
  l1,l2:longint;
begin
  // l1 and l2 are longint variables as the arguments passed to the 
  // DLL are longint even though the data is actually 8 bit

  l1:=can_dmx+dmx_offset[channel];
  l2:=c;
  SetData(l1,l2);
end;

begin
  // example call to change the green channel on a can with dmx address 1
  // simply assume that 'can' is not created automatically at startup
  can:=dmx_class.create;
  can.set_channel(1,c_green,240);
  // and so on
  can.free;
end.

When the green channel is set to 240, nothing happens, the lights are fine as they can be controlled from the lighting desk and like I said also by other software that I have written using MIDI show control. However the problem with show control is it is limited to 7 bits, which is why I need this new device to work.

TIA

Andrew

Answer 1

OK, I got the answer from Velleman, you also have to include both K8062e.exe and FASTTime32.dll as well as K8062D.dll in the same folder as your application. Andrew

Answer 2

1. You should use Destroy; override; instead of demolish (to be able to call can.Free).

2. Did you try with cdecl instead of stdcall?

3. I suspect calling dmx_class.finish = StopDevice will stop the device - so you need to wait for something to happen before quitting the application: perhaps the device is closed so quickly that you do not see it working.