Just like how the Atmega328p-pu has its SMD variant, is there a THT variant for the Atmega32u4 or Atmega16u2? If there aren't any variants of those mcus, are there any chips that can interact with USB, while still not needing SMD components added? Much appreciated.
The datasheet for those devices will tell you.
For the 32u4 the Arduino Micro has that processor and it has a Nano like footprint that is through hole and with a micro USB port.
GOOGE : USB to TTL
He needs USB-HID, not TTL serial; he needs something with native USB.
I think the answer is a 32u4 on a breakout board or minimalist development board. You know, like an Arduino Micro. Which also has all the tricky parts of the circuit figured out (USB stuff can be tricky).
Frankly, if you're making your own boards, it it no harder to learn to solder a 0.8mm pitch part like the 32u4 than a through hole one, even using an iron - and it's faster too.
You put a dab of solder on one corner, don't worry i it's bridging a few pads,
Then you use that the "tack" the part in place. Rotate and align the part by remelting the solder and nudgeing the part so all the pads line up.
Easy enough right?
Then comes the magic - get some "no clean gel flux" (only about 80-90% of aliexpress stuff is usable - I got a bogus batch once). For best results, I use Kester RF741 - it's more expensive, but I've not found anything that works better. apply a thin layer of this along all four rows of pins.
Your soldering iron must be temperature controlled. I set mine to 700F, and it's great with leaded solder. Lead free solder from cheap vendors like aliexpress can be a bit of a crap shoot. I bought some "3% silver" (supposedly SAC305, the good stuff, to the extent that any classical lead free solder is good) - 3% silver my ass. It was awful, and the first time I've actually just thrown out a brand new roll of solder in frustration. After unspoolling it i weighed it to find that it was half the promised weight. Try to use good old leaded solder whenever you can 
If it's hard to buy retail in your country, I'm sure the nice gentlemen in china would gladly ship you some for a song.
Make sure you're using a nice broad (not fine point) soldering iron tip (very counterintuitive). I use a Weller LT-series, and the LTKN (knife) is what I always default, though in tight spots, a CC, or BB bevel ones works great (and can be better for clearing and bridges). If ou don;t have any of those, use a somewhat broad chisel point.
So now you have the best tip you own on the iron and flux on the places you'll be making joines, and the tack in one corner is holding it in place, Starting from the opposite corner, put a bit of solder on the tip of the iron. Touch it to the end of the row of pins and smoothly drag it along the row of pins. When the smoke has cleared, you should find that all the pins are beautfully soldered. If all of them are bridged, yo used too much solder. If the ones at the end you did last aen't soldered, yoi needed to add a bit of solder diuring the process.. Repeat on all four sides. Inspect for bridges. bridges can be cleared by melting the solder and dragging away with the tip of the iron (if all the flux has burned off, add a bit more) . If there's just too much solder on a row of pins desoldering braid with clear it up in a jiffy (again, flux is essential. Never try to solder them 1 pin a a time, it never works, you want to solder one side at a time.
I would rather solder a TQFP-32 over a DIP-28 any day of the week. I've tried dirty tricks like using flux and a knife shaped tip, and "drag soldering" the through holes, I've tried solder paste wit a similar strategy. No, there is no way you can solder a DIP part faster than a similar SOIC or 0.8mm pitch QFP, and it doesn't take much practice to get the hang of it.
The finer pitch QFP parts (ex, 0.5mm pitch) those get a little tricker no matter how you do them, because there are so many ways they can be misaligned, and it's easier to bridge pins, But it's essentially the same thing. Same goes for TSSOP. Actually, my yield with practice using a real reflow oven on QFP-64 is around 50% w/no easily cleared bridges, and around 80% if you only count ones that are misalgned as failures; those need a hotplate to rework, but can be fixed easy-peasy on my UYUE 946C cheapo chinese hotplate (hand soldering, my yield is almost 100%, but is a might bit slower than just popping it in the reflow oven)
The most important thing is making sure it's aligned at the start, and that it doesn't just look aligned on 3 of the 4 sides.
If you tweak the land pattern by narrowing the pads on the PCB slgihtly, it gives you more margin for error.
IME, when it gets challenging is when you need todo a QFN or DFN package with an iron (unless the footprint is designed for hand soldering with long pads and a way to get the exposed pad from below). I break out the hot plate for those (also great for modules with castellated pads) or if I need to rework a misaligned QFP. Assuming you have reflow or a hotplate, what's really counterintuitive is that while QFP's get harder as the number of pins increases (the self -centering effect doesn't get stronger, wile smaller angular misalignments become fatal). QFN's get easier, because of that center pad and the self-centering effect.
Obviously for passives and other really small parts, reflow >> all, but it's not hard to solder 1206 or 0805. what you do is put some solder one of the two pads for each passive, then solder that (holding the part with tweezers). use tweezers to then push down on the part and briefly reflow if it it ended up far from the surface of the board. Then when you're all don with that, for all parts, you go back and solder the other side, IMHO, you get more out of reflow for passives and stuff like SOT-23 than you do for QFP and SOP , which are readily drag-solderable.
Drag soldering is truly magic. You wave your wand across the row of pins, and with a puff of smoke, it's soldered. I taught that to an assistant once, and within minutes, he was drag soldering parts on like a champ. It's no harder to learn than through-hole IMO shrug
You can also look at this video for simple soldering SMD parts : EEVblog #997 - How To Solder Surface Mount Components - YouTube
I'd recommend starting only at 6:00 unless you can bear the guy's incessant talking and squeeky voice. He uses an iron with a concave tip.
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