CC3D Atom OpenPilot Flight Control Board Authorized ... LMAO.
CC3D, Atom, and the first two boards you linked are all electrically identical (OK, programatically identical). The code can't tell the difference. They are all CC3D's.
My guesses: Revo Nano (slower, 100mhz CPU and no telemetry on board) came along at the end of OpenPilot's life and was a bit expensive when compared to full featured Revo clones. I suspect the main people legitimately interested were racers but other boards with other firmwares were at least cheaper if you only wanted racing. These other boards were hotly hyped by startup firmware groups. There was also a fervor for the Nano when it first came out, but to me it seemed more of a bubble that went away as OpenPilot faded.
Up until about early 2018 you could still buy authentic Nanos, and for a good, clearance price. That batch went away. You can still buy the clearance of the last of the authentic Sparky2's (black PCB and perfect) on eBay. I don't know where you might get an authentic Revo, other than from an end user.
The last board you linked to is a Revo Mini which is electrically equivalent to a regular Revo (168mhz CPU) that has the telemetry removed. It is not a Nano. You can buy the missing telemetry module called an OpLink Air, but why not just by a Revo then? Perhaps this Revo Mini is a good FC for someone who doesn't or can't (e.g. illegal frequency) use telemetry. FYI: "next" has support for other telemetry frequency bands; that basically requires replacing the Revo's / Sparky2's / OpLink's RF daughter board to change from 433mhz to 915 or 868. Very good soldering skills and tools required. I am not aware of any of these boards (Revo / Sparky2 / OpLink) being available on 915 or 868, but there are undoubtedly some out there done in very small volume, at least for personal use.
All that is left of any of these are clones, although there are some originals around. In order of clone volume (my guess):
- CC3D and variants
- Revo and variants
- Sparky2 (no variants that I know of)
- Nano (one variant on a Revo sized board existed that I know of)
Historical note: What we call a regular Revo now days was actually initially called a Revo Mini because there was an unreleased full size Revo. TauLabs and derivatives still call the regular Revo a Revo Mini.
The cloners have completely bastardized the names CC3D and Nano and add these two words to any boards associated with OpenPilot, just to get people to click and look. Atom is not far behind.