I've got myself a huion camvas 22 which is a great drawing tablet, except i really miss the side keys i had on my older smaller XP-Pen. This is such a hassle not having a wheel with which i can zoom, rotate and change the brush size with my left hand while drawing with my right hand, that i decided to do something about it. So i've come up with this very simple and maybe a bit underwhelming mounting design for a simple macro pad that would be attached to the tablet. So far it seems to work
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the thing put together and clamped on the tablet (don't worry about the screen scratching, there is some squishy tape and foam seal under the "clamp" part
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this is how the "clamp" works, you just manually adjust it and then torque down those three nuts. Of course the great rounded design of the tablet makes it much harder to make it work...
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A single pro micro is more than enough for 8 keys + a rotary encoder with a pushbutton. so technically that would be 9 keys. Each switch is wired to an individual pin, there is no matrix whatsoever to make things simple. Keys are from a broken NTC board (i got 4 other working ones) and switches are some cheap chinese "alps" clones (they are more like APC clones) i bought out of curiosity on aliexpress some time ago, they are clicky
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Of course it's not finished yet as it's missing a cover for the case. As the rest of the chassis this will be 2mm thick aluminium with a place for a USB type B because i like the shape of that plug and i have a nice printer cable for it. I don't really trust the pro micro connector for a longer use..
If anybody is curious how the keyboard is made it is a punched aluminium sheet, bent and laser welded (the switch plate to the rest of the "clamp" body.) the nuts are placed on bolt inserts, which are pressed into the sheet so you don't need a screwdriver and a nut driver to bolt the clamp up, like you would have to with normal screws.
i wouldn't consider it overkill as this is pretty much a remake of how my XP pen tablet was, 8 buttons and an encoder. But you could say it's a bit more "robust" 
