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91
GCS General / Re: How get relative to ground altitude?
« Last post by Marico on July 16, 2021, 03:03:46 pm »
I recall that OSD also does this for you so it shows friendly numbers in goggles.

I have an old OSD module which requires a typical NMEA GPS. AFAIK Revolution can output telemetry data on selected ports.
Is this telemetry data just "emulate" real GPS output, so I can connect Revolution telemetry output to GPS input in my OSD? Or Revolution require dedicated OSD module (MinOPOSD)?
92
GCS General / Re: How get relative to ground altitude?
« Last post by TheOtherCliff on July 16, 2021, 01:45:48 am »
Sorry, I focused on "relative to ground" and first thought is that GPS/baro doesn't do this on the side of a hill.

PFD on FlightData page is relative to HomeLocation.

System -> DataObjects -> PositionState is relative to HomeLocation.

I recall that OSD also does this for you so it shows friendly numbers in goggles.

Just re-get HomeLocation before you take off (so that HomeLocation == ArmLocation == TakeoffLocation).  With USB or OpLink telemetry connected, a good GPS sat count, and aircraft sitting where you will take off, go to Configuration -> Attitude -> Settings -> HomeLocation and press the Clear button.  In a few seconds it will display the new HomeLocation.  The only problem with this is if you are using Waypoint flight, and your waypoints are relative to HomeLocation, you just moved all the waypoints.
93
GCS General / Re: How get relative to ground altitude?
« Last post by Marico on July 15, 2021, 11:50:57 pm »
This requires a sonar or something similar.  A sonar sends a sound pulse and measures the time it takes to bounce back.

Why not use GPS? Is on the board already.
Couple years ago I made a small GPS+mcu+3 digit display module, there was a button for set base altitude  at ground level before fly. During fly it substracted stored base level from current level and stored  such calculated maximum value for later reading. Many OSD systems show (relative to ground) altitude calculated from GPS. That's all I need.
94
GCS General / Re: How get relative to ground altitude?
« Last post by TheOtherCliff on July 15, 2021, 11:30:30 pm »
This requires a sonar or something similar.  A sonar sends a sound pulse and measures the time it takes to bounce back.

Sonar only works when within range of the ground (a few meters).  That range depends on what the ground is made of.  Soft thick grass has short range.  Cement has long range.

I wrote some test code that uses sonar and when the sonar is within range (the sonar tells you if it within range) then the absolute altitude was changed into altitude above ground.  The result was that you could fly up and down a hill or steps using the current altitude hold/vario flight modes.

I found that you cannot use a cheap sensor because the prop noise fools a cheap sensor that is out of range into saying that it is staying at that max range instead of saying it is out of range.  I bought a good sensor that uses some of the same technology that cars with radars use to avoid hearing other similar cars, but had moved on to other projects by the time it arrived.   ::)

A quick search on the wiki returned these links which themselves contain some links:

theothercliff (me) video of climbing stairs and link to code repo
  (look earlier in this thread for some links)
https://forum.librepilot.org/index.php?topic=3390.msg23410#msg23410

mr_w sonar code branch and discussion
  (I think it only updates the sonar altitude number which is not currently used for flying?)
https://forum.librepilot.org/index.php?topic=767.msg5504#msg5504
95
GCS General / How get relative to ground altitude?
« Last post by Marico on July 15, 2021, 10:24:37 pm »
Hello,
Is there any way to display (on a gadget) altitude relative to ground calculated from GPS (from formula: current alt - armloc alt)?  All available altitude related gadgets display altitude values in "non friendly" units (like baro in pressure or GPS gadget shows alt  above sea level).
96
Hardware / Re: How activate a buzzer when there no free rc channels...
« Last post by TheOtherCliff on July 15, 2021, 08:50:41 am »
Thanks for posting.  I would have assumed it was not possible from your results.
97
Hardware / Re: Auxmag axis z stays unchanged.
« Last post by TheOtherCliff on July 15, 2021, 08:49:27 am »
I guess I didn't know you were using NMEA.  I had tried that in the long ago past and got a slowly oscillating attitude while sitting motionless on the ground.  I recall that it is because EKF (INS13) needs velocity data to converge well.  Ublox protocol has velocity data, but NMEA does not.

NMEA is only useful for position on map, not for GPS flight modes.

Glad to hear you got it working.  :)
98
Hardware / Re: How activate a buzzer when there no free rc channels...
« Last post by Marico on July 14, 2021, 10:41:15 pm »
That's strange. I attempted a second try to configure buzzer with "mirrored" PWM channel and now it works! I configured Accessory0 to the same input channel (5) which controls flight modes and I routed it to output channel #5 where buzzer is connected. My flight mode (switch) is configured to 3 positions, when I switch to 3 buzzer is activated. Nice.
 I have no idea why earlier status board reported input error and refused to arm....
99
Hardware / Re: Auxmag axis z stays unchanged.
« Last post by Marico on July 14, 2021, 10:30:44 pm »
I replaced failed aux magnetometer and GPS too. I bought a GPS module with magnetometer (ublox m8n + HMC5883L). I extended tail a little bit to mount it away from the wires and voila! After calibration Aux error rate is below 2% with running  motors (!). Now all GPS related flight modes seems to work correctly.  I just made only one test flight before it got dark, can't wait to test it more.
 I think my GPS related problems were caused by too slow (previous)  gps module. There is no direct/clear info in howtos saying "don't use NMEA only based GPS for gps flight modes, is too slow). I think GCS GUI should display such warning when user select  nmea protocol with GPS related flight modes...
100
Hardware / Re: Auxmag axis z stays unchanged.
« Last post by Marico on July 14, 2021, 10:18:22 am »
I don't have much hope, but to degauss you need to use a soldering gun, not iron.  :)

Gun has a coil of wire that acts as part of a transformer.  Iron is just a resistive heater.

LOL, of course I meant a soldering gun not iron.  ;D
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