Liberally Apply Test Points (EE Tip #144)

When I first started designing, I did not understand the need for the scope posts for hardware test points. I could always tack on a wire or, with many through-hole parts, connect my scope right to the chip. But now test points are essential. My eyesight and steady hands are long gone. But it goes way beyond that. Many of the scope points are buried under the chips. And those that are exposed are smaller than grains of sand. Provide yourself access to the critical points.

Thinking about where you’ll want to probe the  software can also be useful. Linux has done a great job by providing hundreds “test points” for the OS. We should learn to do that with our applications. Planning in advance the places you want to test is also a useful exercise in the whole development cycle because early on it forces you to think about testing.—Bob Japenga, CC25, 2013