What connector to use on target board?

granddad said:

One ICSP connection i came across ( not sure where ) had the 6 pads and holes for male type header pins, in a line but slightly offset to each other , so a pin header just pushed in and made a tight connection ok for a single or occasional program.

Click to expand...

I've done a few just on the bare straight holes, but some others have proved impossible to get to work.

granddad said:

One ICSP connection i came across ( not sure where ) had the 6 pads and holes for male type header pins, in a line but slightly offset to each other , so a pin header just pushed in and made a tight connection ok for a single or occasional program.

Click to expand...

Sparkfun designed those footprints, calling them "lock" connectors. The holes are slightly offset from centerline alternating above and below connector centerline. The intended purpose is that it keeps headers perpendicular to the board while they are soldered in place. Sometimes, when the pad plating is just right, the header fits very tightly like a plug in a socket.

If you use EasyEDA, I have created lock footprints for a range of headers and Molex KK connectors. I have made one change from Sparkfun's footprints – the center of my footprints is properly placed at the center of the pins, rather then being centered on pin 1. If you'd like to use them, let me know and I'll tell you how to find them (sorry, it's 3am, and I don't recall my user name at the .moment).

See this post for an illustration and more info.