Not enough pins! (MEGA Screwshield)

After connecting up the ultrasonics and IR sensors to the board I started looking into how many I/O pins I had left on the Arduino Duemilanove board. The VNH 5019 Motor shield requires 8 digitals and 2 analogue pins. This left 6 digital pins and 4 analogues, of which 3 ultrasonics needed 3 digital pins and the IR sensor an analogue, not much room for expansion!

Something bigger and better was needed....the MEGA :) 54 digital pins and 16 analogues should allow plenty of expansion!




While playing about with the motors I realised that just pushing wires into the Arduino headers wasn't a great solution, any slight knock/bump and they'd fall out. While Screw Shields are common for the standard Arduino's I couldn't find one on the market for the Mega.

Setting about designing one I realised a small design issue with all Arduino's. The digital pin headers between Digital 10/9/8 and the next header 7/6/5/.. is a distance thats not a standard strip board pinout. All the other headers line up with a strip board apart from these two.

As I was planning on still using other shields, I just cut a section out. I didn't bother with bringing VCC and RESET pins into screw headers and originally planned to duplicate the 5v / 3V / GND pins on both sides of the shield however couldn't think of a tidy way of doing it. Not all pins are taken to screw terminals but this should give me enough I/O (famous last words!).

As I wanted to bring some analogues out to screw headers I kind of lost the space needed to bring both rows of digitals out.

All mounted, just needing the sensors wiring in then I can finally start programming something useful.