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What are/What use have these pads near the ATmega chip?

Arduino Yun contact pads near the ATmega chip

I thought they are used for testing or something else, they seems to expose the ATmega traces directly.

Maybe they can be useful to connect to the chip by directly soldering a ribbon cable to the pads.

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up vote 9 down vote accepted

They look like the footprint for an alternative package, probably the TQFP-44 variant. Having both footprints: QFN (the leadless package that is installed) and the alternative TQFP variant allows a single board to be used depending on the availability of either part for more flexible BOM management. You could also use it for testing, as originally suggested as well.

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Nailed it! Also you can use them by connecting a logic analyzer to the pads should you need to debug a design – Funkyguy Aug 18 '14 at 16:32
Wondering if there is some testing rig available on the market that has a TQFP-44 connector (something like this JTAG connector: m.eet.com/media/1002764/1tag.jpg ) – Madarco Aug 18 '14 at 17:14
Most likely, you are better off soldering a ribbon cable up to the pads on the TQFP footprint. Most removable clamps require the actual chip to be installed, are quite expensive, and don't really go down to something as small as a TQFP-44, for example, these start at 80 pins: winslowadaptics.com/… – Zuofu Aug 18 '14 at 19:34

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