Here is my first attempt at a home-made Omnibus interface card using these adapters.
It's a mash-up of the boot-loader designs by Malcolm Macleod and Roland Huisman, plus some extra stuff (power supply voltage monitoring, and provision to read the memory address and memory data buses)
Yes, I do know about professional fab houses that are some or all of: cheaper, faster, easier, better. (I just had 5 different designs done that way a couple of weeks ago).
But I want to explore the limits of what I can do at home, especially when my design may be total rubbish, so I don't want 5 expensive copies of a failure.
It may also be easier to "bodge" on fixes with a DIY board (wider tracks & spacing, no solder mask or copper fills), which is desirable for development.
Single sided PCBs are more practical for DIY, so that's what I did, using wire links on the "solder" side.
That was the worst part of this project - next time I would try to do double sided.
Being a DIY board, and single sided, I decided on surface mount because:-
* Less holes to drill
* No pins on the "solder" side, so wire links can run under components without interference.
* Smaller components leave more space for traces.
Even the through-hole style Arduino was mounted as an SMD.
I used the "toner transfer" method, which went quite well:-
As did the etching (I don't know why the forum software insists on rotating this one to vertical) :-
Then came the drilling, this took about an hour:-
The bottom rows are 1mm, most of the others are 0.8mm. I would have preferred 0.6mm, but all my bits of that size are now broken. Only one 0.8mm bit broke doing this, but probably more 0.6mm bits would have broken if I had any.
Then the many wire links:-
This took several hours, and I would not do this again. Next time I'll try double sided, and if that doesn't work, it's off to the fab...
The 0.8mm holes are a bit too big for the via sizes used, so I'm expecting some problems with dodgy joints on some of these.
Finally, all the parts soldered on:-
Because it's single sided, the 40-pin adapter connectors are on the other side, so that the pins can be soldered on this side.
I still need to make a couple of small 4-hole plates (probably from FR4) to bolt the board and adapters together.
Glue used to keep the wire links from shorting:-
Over the next weeks, I'll try to get this thing to do something useful...