> View over 200 data points collected every 1/10 of a second during the flight
Is there some significance to these numbers (20 seconds and 30 seconds of data) or is that just an attempt at "big numbers sound good"?
PX4 also has lots of "topics" logged at around 1/10, e.g. hover thrust estimate every 100ms:
https://github.com/PX4/PX4-Autopilot/blob/main/src/modules/l...
Running on a single-board computer with an applications processor like a Raspberry Pi or BeagleBone, with multiple cores at 1 GHz+, gigabytes of DDR3, with on-chip SDXC drivers? Logging loads are irrelevant. The only thing to watch out for is that if you want to use the logs to figure out why you had a catastrophic crash, the OS may have write-buffered a lot of data in RAM.
If you're running on a crossover MCU, like a Cortex M7, with a core or maybe two at a couple hundred MHz? Think about it what you log.
Running on a Cortex M3 with a few dozen MHz and a few dozen kB of RAM? Yeah, appending to and rolling over a whole 512-byte page in RAM and finding the time to push it over the SPI peripheral is going to be tough, you may want to use a binary protocol so you're not burning unnecessary cycles in itoa() and you get more data per byte of buffer.
The DJI drones discussed here have big Cortex-A53 SOCs that are already logging 4k video at 30 FPS to that SD card; the log file is only noticeable as a distraction from that task. I think the crossovers are the sweet spot, though, because a 'fast' clock or interrupt on that Linux board is slow in comparison to the more tightly integrated RTOSes.
The generic data channels number easily less than 50 - time, X,Y,Z, axis velocity, battery life, yaw, tilt, pitch, etc.
I dare say some of the special domain applications generate more channels of data from mounted instrumentation - all logged to a common DJI family log format - for extraction on landing or broadcast during flight etc.
The 200 channel Vs 300 channel thing is likely just poor copywriting from looking at max channels in two different application areas.
On top of that come RTK and ADS-B receiver data, and the really large ones (Matrice, Agras) add more engines, payload status (weight, flow rate), multi-battery health, RF quality and other data channels.
To be honest, it's amazing just how many features modern drones carry while still allowing sometimes well over half an hour of flight duration.