Thanks Nick - ill give that some thought.
In terms of freeing up IO pins, in most case IO pins arent an issue. Since each board has a specific function, anything over and above those functions is effectively wasted. Ie, for the high speed counter board, I really only need 4 pins (if you ignore the address pins). The board cant really have any more inputs than that as I need the processor to be able to count really fast. ie a Test I did was it to read 10,000 pulses a second. If I had more than 4 inputs, then I am not sure if the uC would handle to count 4 channels at that rate. Ideally the 2 External Interrupts is all I wanted, but I put 2 Pin Change channels on there too, just incase there is a need.
Next week I am taking this out to a mates place, who has a function generator. I will crank that up and see what the limitation is of the uC and the software I have written for it. I can then determine if more inputs are appropriate etc
So yeah, it would be nice to get rid of the dip switches, but to do it to free up IO probably isnt the driver.
In the case of the General IO board, then yeah - fair point.
If I keep the same sort of size terminals, then I can fit 12 wires. They are 5mm pitch terminals so on the large side, maybe. I might look and see what the next step down is, probably 3.x I would think. That said, most boards are not restricted by the terminals, but of real estate due to the large through hole components, track size that I am restricted to with my current printer, not being able to have plated through holes so lots of manual vias, etc etc.
But yes, lots to improve on.
Ideally I want it to be all SMT, but its not really achievable if I am assembling myself, and I dont have the money or customers to make 100 of each board and get them assembled professionally.
Quite a lot of parts used were free samples I managed to get from manufacturers. ie the MAX127's I got 5 samples after pushing really hard. These are not cheap chips, about $58NZ from Digikey each!
Sample wise I dont have a huge amount left. I may be able to make another partial set, I am not really sure.
I would quite like to make this a backplane system too, rather than a stacking system, so modules can be inserted individually rather than stacking together and having to unbolt them all to get at one in the middle etc. More thought is needed though. It shouldnt be hard to do though, take off the stacking spine, and put 90 degree ones in, and then make a set backplane which takes like 15 modules or something, and then plug them on and attach them somehow. I wouldnt need headers top and bottom of each boards then, only 1 side as the backplane will join everything. I probably wouldnt need to change much at all to achieve this. The 2 6 pins headers that feed the ethernet board etc I would have to do something about, but that should be ok.
Lots I could do.
Any more ideas anyone - I need ideas! I want to keep improving, and the more improvements I can make each revision, the cheaper the overall project will be. Each revision is destructive too, as I need to pillage parts to make the next one. A little tricky with the SMT stuff though.
small steps James, small steps.