On the BMOW Blog, they are continuing to research options for alternative programming headers for AVR microcontrollers.
For one-time programming purposes, the standard 3 x 2 pin 0.1 inch header is just… too big. I’m on the hunt for something that’s smaller, and that can be used on a bare footprint without actually soldering a header. The mockup above shows a 1.5 x 1.5 inch board with the options I’m considering, along with size references from a 32-pin AVR, an 0805 resistor, and a through-hole resistor.
They are exploring a number of options:
A – The standard 3 x 2 footprint for 0.1 inch pin header.
B – 3 x 2 pin 0.1 inch footprint with zig-zag or lock hole spacing. This helps temporarily hold a header in place through friction.
C – 3 x 2 footprint for 0.05 inch pin header. It’s a lot smaller, but the hole spacing is tiny.
D – 3 x 2 pin footprint with zig-zag spacing for 0.05 inch pin header.
E – 3 x 2 pin footprint for pogo pins with 0.05 inch spacing. It’s nearly the same as C, except the drill holes are smaller. It’s designed for something like the Pogo Key, where the tips of pogo pins snap into the holes, but unlike C the pins don’t actually pass through the holes.
F – An alternative footprint for E. Two positions are holes to help align and stabilize the Pogo Key, and the other four positions are one-sided pads, so more of the PCB’s bottom side is available for other traces and components.
G – 6 x 1 pin footprint for pogo pins with 0.05 inch spacing, inspired by the Pogo ISP Micro. It’s essentially a Pogo Key with a linear layout instead of rectangular.
H – An alternative footprint for G. Two positions are holes to help align and stabilize the pogo pin adapter, and the other four positions are one-sided pads, so more of the PCB’s bottom side is available for other traces and components.
I – 6 x 1 pin footprint with zig-zag spacing for 0.05 inch pin header. Example
J – An alternative footprint for I. The six pins are split into groups of four and two, to prevent backwards insertion of the header.
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