Beta mavlink2: onboard camera capture

[julianoes]

This adds the mavlink mode CAMERA which sends the following to an onboard camera module connected to the FMU:

• heartbeat
• attitude
• global position
• camera capture command on if armed and off if disarmed

start the mode on Telem2 (on Pixhawk):

   mavlink start -d /dev/ttyS2 -b 57600 -m camera

[DrTon]

@julianoes, just to let you know (if you really need it): you can set rate for some messages (e.g. for GLOBAL_POSITION_INT in your case) depending on desired data rate (-r option of mavlink start), see "normal" mode and rate_mult. I.e. if user wants to have 5000 bytes/s total rate, he will get it, filled with useful messages.

[julianoes]

@DrTon ok thanks but I don't have to? As it is, it's ok, right?

[DrTon]

I think it's better to have this feature, to allow users to use more fast or slow links on 100% without additional streams configuring. Add it please. I think for ATTITUDE, GLOBAL_POS, and maybe CAMERA_CAPTURE (your decision). And tune values to get approx. desired data rate. And in your script you can simply set -r option to get resulting message/data rate that you want.

[julianoes]

@anton: I added the rate multiplier.
How do I have to tune it? I just set -r 1000 in my startup script at the moment which gives me the desired 20Hz.

[DrTon]

Can you check total data rate on serial port? If it is ~1000bytes/s then it's ok.

[julianoes]

Hm, QGC says 1.4kB/s but that's in Bytes, right? And your -r is in bps so bits per second? Or maybe your warnx should say Bps?

[DrTon]

-r is in bytes per second. So you need to set something like 10 * rate_mult or 15 * rate_mult. (for -r 1000 rate mult is 1.0).

[julianoes]

Ok, I corrected the warnx to Bytes/s since bps would be bits/s: a989dd6
Also the rate of the camera mode is now around 1kB/s.
From my side, this is ready to merge.

[DrTon]

Yes, bytes/s is more clear, it was changed to bps by Lorenz, I don't know why :) Ok, great, then it can be merged, I think!

[LorenzMeier]

@julianoes @DrTon Once this is updated with beta_mavlink2 I think its good to merge.

[julianoes]

Merged. Compiling but untested.

[LorenzMeier]

In case you get a chance to test it I think we could go ahead and merge.

[julianoes]

Tested on bench, works fine.