From Andreas Grotz 2006-09-03

ah trigger one more part ...

BD ** BE 00 E0  is not the header

the Frame-packet starts with E0 and ends with "BD ** BE 00"


> > so what did i did .....
> >
> > i sniffed the usb-traffic in windows and made an finger-scan ... after
> > that i created a Visual-Buffer-Analysis tool .. so i quickly noticed
> > where the Frames are .. the Interessting point now is the
> > following ... the images seem to be 63 bytes width and like 1700 lines
> > height (63*1700 bytes) .. mhm ...
> > i moved these 1700 bytes of each frame into an buffer and did some
> > byte-to-bit-to-image thing ...
>
> A bit strange in their datasheet (short) the mention 192 pixels x16
> lines.
> One fingerprint 1700 lines means i have to change that part (skipped it
> to 160 for my program)
> For their other chips the use 1 pixel is 4bit.

> > the interested part is that the device has an extrem
> > high-framesPerSecond-Count so in a driver we would have to compare
> > eache frame with another and process them to one finger-print ..
> > (seams the real hard part)


i finally did it ;) i've the complete scanning-frame-seq. attached
the scanner works like an Optical-Mouse ... the first 10~20 frames are dump,
when the finger-print gets recognized by the device the frames are only 
transmitted if they can be attached to each other, so it is just neccessary 
to detect when the frames are Ok (perhaps for this case there is flag in the 
proto) and then have to attached below each other and finish.

after all i just triggered the IMAGE-Response-Header:

// 02 BD 74 BE 00 E0
// 09 BD 6E BE 00 E0,
// ** BD ** BE 00 E0 <IMAGE CONTENT>
//     ++      ++   ++ ++ i scanned the log for these 4 bytes and triggered 
160 frames in the log file

So every Image starts with  [0xBD] [0x??][0xBE] [0x00] [0xE0] [192*8 Bytes]
 (4 Bit per Pixel works just perfect right)

Now the Image-Processing showed first just a repeating thing but not a 
print ...
i triggerd out the 192x16 is true "BUT" its not the Image-Direction ...
192x16 would normally say X=192, Y=16 .. right ?
in this case the Sensor works so:
X= 16 * 4 Bit with 192 lines .. (just rotate the device 90°degrees *g*)
Working:
for ( y = 0; y<192;y++) for ( x = 0; x<16;x++) pixel[x,y] = buffer[offset + 
((y*16)+x)];
Aspected:
for ( x = 0; x<192;x++) for (y = 0; y<16;y++) pixel[x,y] = buffer[offset + 
((y*192)+x)];

so on scanner line is just 16 Pixels and not 192 ...

and the image-buffer have also to be rotate ..
  // display xbuf
  a:=0;b:=0;x:=0;y:=0;
  for cd:=0 to (192*16)-1 do
  begin
    a:=xbuf[cd];
    inc(x); if (x>16) then begin x:=1;inc(y); end;
    form1.pbf.canvas.pixels[y+xp,x+yp]:=rgb(a*8,a*8,a*8);


(heres the complete magic code i used (delphi) )
var yp:word=0;
    xp:word=0;
procedure extract_frame(ofs:longint);
var x,y,cd,l:longint;
    a,d,b:byte;
    xbuf:array[0..192*16]of byte;
begin
  cd:=0;
  fillchar(xbuf,sizeof(xbuf),0);
  for l:=ofs to ofs+192*8 do
  begin
    b:=buf[l];
    // split Byte at offset l to b1 and b2
    b1:=(b shl 4);  b2:=(b shr 4);  b1:=b shr 4; // shift l, shift r...
    if (cd <= 192*16) then
    begin
      // fill xbuf with new 4 bit pixel-data
      xbuf[cd]:=b1;inc(cd);
      xbuf[cd]:=b2;inc(cd);
    end;
  end;
  // display xbuf
  a:=0;b:=0;x:=0;y:=0;
  for cd:=0 to (192*16)-1 do
  begin
    a:=xbuf[cd];
    inc(x); if (x>16) then begin x:=1;inc(y); end;
    form1.pbf.canvas.pixels[y+xp,x+yp]:=rgb(a*8,a*8,a*8);
  end;
  /* ----------------------------------------------------
     ******* ATTENTION ****** Thats Point i mententioned above.
     ---------------------------------------------------- */

  // next frame below this one, and at end cont. on top right side
  inc(yp,17);
  if (yp > form1.pbf.height) then
  begin
    yp:=0;
    inc(xp,195);
  end;
end;

// scan the extracted incoming-usb-log-traffic and seek for the image header 
// BE 00 E0
procedure TForm1.Button8Click(Sender: TObject);
var frames,l:longint;
begin
  pbf.left:=pb.left;
  pbf.width:=form1.Width;
  pbf.height:=form1.height;
  pbf.Canvas.FillRect(rect(0,0,pbf.width,pbf.height));
  frames:=0;
  // ** BD ** BE 00 E0 <IMAGE CONTENT, 192*8 Bytes>
  for l:=1 to tp-10 do
  begin
    if (buf[l] = $BD)and
       (buf[l+2] = $BE)and
       (buf[l+3] = $00)and
       (buf[l+4] = $E0) then
       begin
         // we got an image
         inc(frames);
         extract_frame(l+5);
       end;
  end;
//  memo1.lines.insert(0,':: '+inttostr(frames)+' Frames Found.');
end;