8 Dec
2011
8 Dec
'11
10:37 a.m.
On Dec 6, 2011, at 1:52 PM, Richard wrote:
> I've got a bunch of Nuclear Data peripheral
circuit boards that I need
> to reverse engineer. They are simple circuit boards with all the
> tracings visible (i.e. no internal layers) and the parts are all 7400
> series logic in standard DIP packaging.
>
> If I were to do this manually, I would take high resolution
> photographs of both sides of the board. From the photographs, I would
> try to recreate engineering drawings: part placement and circuit
> topology.
>
> I'm wondering what kind of tools are out there that would assist in
> this. Could I process the photos to extract the topology of the
> printed circuit traces? Can I correlate this with image recognition
> of the part packages and combine them to product a netlist?
>
> I'd appreciate hearing any experiences from others that have reverse
> engineered circuitry.
My experience reverse engineering the ETH Lilith :
around 10 PCB's ( omnibus size, they even share the same card edge connector )
Mostly TTL, dual layer, ranging from not pariticular dense ( the CPU, AMD2901 ) to rather
dense ( Ethernet card, in TTL)
Total number of IC's : ~ 500
Method used : Eagle CAD program.
Enter all IC's, with correct instance names , as on the PCB.
Start measuring !
A really good connection tester is indeed a requirement, mine has less than 20 mV
output.
This ensures diodes and circuit protections are not falsely seen as connections.
Wire up the IC's in Eagle, move and group functional blocks as you see fit.
The result can be downloaded from ftp://jdreesen.dyndns.org/ftp/CAD/
Take a look at "magnet.sch"
This is the ethernet card and is the only schematic that is not fully done ( around 75 %
finished), it gives a good idea how i worked.
Total time take 2 months, 1-2 hr /day.
Of course , a few months later I could find the original schematics at the ETH...
These are now up on bitsavers.
And I did ask before I started, but asked the wrong person.
It did enable me to find some bugs in the original schematics though !
Jos, whos Lilith is now running again after many fruitless hours with the oscilloscope,
and 2 drops of oil on the right spot ( voice coil carrier ball bearings )