Understanding the protocol

[IamTheCarl]

I wanted to learn how to communicate with USB devices.
I felt re-implementing this library would be a good exercise.

I've got communications with the device and can successfully query the firmware version.

But there isn't much explanation on how this protocol works.
Like I see many lines of code like this one:

UP3D/UP3DCOMMON/up3d.c

Line 36 in 7e73e2e

(6 != resp[4]) )

Does the number six represent success?
Is there documentation on this protocol or did you just reverse engineer the protocol for these printers?
If yes, what tools/processes did you use to reverse engineer the protocol?

[kscheff]

Maik reverse engineered the protocol by recording and exploring the USB traffic. You can read about this on his blog: https://www.stohn.de/3d/

[IamTheCarl]

Thabk you for that.
Maybe I'm navigating the website wrong, because while there are articles with titles that sound like what I want, they are only pictures and videos.