Reverse Engineering
Contents
In edition "design station"...
The problem: You got an old, defective PCB bare of any documentation or CAD data. Unfortunately this circuit controls your Bucket Wheel Excavator, Rail Car, Ferry Boat, Aeroplane, Locomotive, Rack Railway or whatever industrial equipment standing idle non-productively because of electronic damage. The manufacturer is no longer on the market, service companies can not be found. So if you don't want to scrap your machinery the only way is rebuilding the defective PCB. But even for experienced developers this method is a demanding challenge even if there are only few parts in the game.
The solution: By the help of a netlist TARGET 3001! creates a schematic including the part namings as well as the signal names. A new PCB layout now can be "cloned" from the old.
The company Diagnosys offers the PCB diagnosis system "Pin Point", which creates the netlist needed by an electronic sampling process. Using a special heuristic method in TARGET 3001! the complexity of this ratsnest is reduced to a minimum. Components and signals get spread over different schematic pages by a Simulated Annealing algorithm. From there a new PCB layout can be created using all tools of TARGET's PCB creation. This feature only is available in edition "design station".
Reverse engineering in all editions
Now if you want to re-edit or modify the layout your job is to redraw the complete layout (Reverse Engineering). In this respect it is fine to use an image of the layout as a default in TARGET 3001!. "But an image of the layout is only a kind of painting which will not provide any pad and track or groundplane information" you might argue. You are right. But nevertheless an image as a default is a great help for locating packages and redrawing the connections. Place the image beneath your layout in TARGET 3001! (upon layer 0=area bottom) and place all elements upon it. Later when your layout is finished, you can delete the image.
Take a bitmap (= an image having the file extension *.bmp) to your clipboard and insert it into a color filled rectangle which you had placed upon layer 0 .
Use the "transparent...opaque" slider in the "Load picture into rectangle" dialog to determine the opacity of an imported image. So you can look a little through your photo of "copper top" to see what is happening on "copper bottom". Exact placement of housings and traces on both sides is then easier.
Now place all landmarks (pads), tracks and all other elements upon higher layers. First make sure that your visible screen is set to real size in mm or inch. See menu "Settings/Settings / Options". In this dialog look for "Usable monitor size" and enter the measurements of your screen (take a fold-rule and hold it on screen to figure it out). Otherwise you might suffer deformation. Now act as follows:
How to proceed
1. Step: Create a bitmap of your board
Measure the dimensions of your hardware board as it shows in reality. Create a bitmap of the layout you have. A scan of a board might have advantages against a handmade photography because of not showing distortions which (slightly) might appear when taking a photograph. Sure you also might use a plot of the layout. Our example board below has a real height of 43,00 mm and a width of 90,00 mm. The cut tips we ignore at first:
Image: A 100% scale scan of your layout
2. Step: Define the board outline
Open TARGET 3001! and select "Create a new PCB without schematic". Now draw a PCB outline on layer 23=Outline using the above measurements. You can use the "outline assistant" in Menu Actions / "PCB Outline Wizard".
You can toggle from imperial scale to metric and back by the use of the function key [F4].
3. Step: Insert the image
Now open layout menu "Actions". Use item "Insert image..."
V18 and before: The size of the image matters since it needs to fit into the predefined rectangle/board outline.
V19 onward: Fitting in of the image to the outline of board or frontpanel is automated.
Image: Load bitmap into area (from version V19)
A larger image will be reduced to the dimensions of the rectangle. In our example we see the component side (top side) of the board. We can import the image as a template e.g. on layer 0, area bottom. In the import dialog we determine the layer for this image. Otherwise, double-click on the image to move it to "0, bottom area".
Image: Double click on an image opens dialog to shift it to a certain layer.
From V19 on, images from the top and bottom side of the board can be imported to different layers. If you reduce the opacity of the image on the top side (see dialog), the image on the bottom side shines through. When redesigning (=for "tracing" by hand ), the top and bottom sides can be viewed simultaneously.
4. Step: Insert components
Now you immediately can start importing components from the database and to place them on the layout at correct position. On the right side you see there had been used a TQFP44 device - get such a package from the component data base...
...and place it. Zoom in deeply and place the package exactly; maybe turn it - or whatever you need to do. Be supported by the X-ray function. Toggle the hash-key [#] on the keyboard to get a "wire edge" image.
5. Step: Draw tracks
Place a smd resistor with a package 0805 and rout the tracks between the pads.
Further steps:
Get in each component package bit by bit and connect them. In our example you see the results in blue, because it's the standard color of layer 16=copper top. If you want to use the bottom side of the layout, you must get in the bitmap already in mirrored shape. The effect is, like usually in TARGET 3001! that you see from top through all layers to the bottom of the board. At the end cut the tips of the outline on layer 23 by using the drawing tool to get the same outline like the default PCB.
Now the placement of packages and connecting tracks is your job...
Finishing work
You may decide whether to add a ground plane after all. Maybe independently from the image. At the very end delete the image and have the layout.