[funtimegrandpa]

Ok,  I have my new revo board installed on my Eachine 250 Racer and everything is working well.  I had some issues with figuring out how to get alt hold to work, but this is what did it.  First you cannot power up in the flight mode that has Altitude setup.  So take off in other than that mode and get to a hover,  then flip to your Altitude Hold mode and things seem to work out good.   I am going to take it over later to where I fly and see how it works real time :-)     

Thanks again,    Grandpa Jake

[f5soh]

That a normal arming behavior.

https://librepilot.atlassian.net/wiki/display/LPDOC/Altitude+Hold#AltitudeHold-Howtouse

"Revo" or "Revo CC3D" doesn't exist, just Chinese marketing.
There is CC3D boards and Revolution boards

[Mateusz]

• Altitude Hold / Varion does not allow for arming for a reason. Which is safety. You can only switch to flight mode with that once you are in the air.
• Check barometer in scopes, is it within +-0.5m Altitude when aircraft is in rest ? If not look at Hardware issues https://librepilot.atlassian.net/wiki/display/LPDOC/Altitude+Hold
• If it still goes up and down check if you have a foam covering baro in the case. Baro is light sensitive and foam is to protect it from wind blowing and propellers but foam must also be thin to pass air flow to the sensor
• If still a problem persist, check if you have vibrations, try increasing accel filtering slightly.
• if it still does not work check vertical PIDs which are responsible for holding altitude (it's a control different from PIDs that stabilize aircraft) you can find those in System->Settings->VtolPathFollowerSettings

If none above helps, god have mercy on you, check one more time all above

[funtimegrandpa]

Ok you made me Laugh :-)    thanks I am going to look at all you said,  but I think I have most things worked out,  a true flight in my open flying area will tell.   I found that I take off in a non alt hold mode,  I switched to the alt hold and seems to be working.  How accurate it is I wont know till later.   But if it is off I will follow some of what you wrote.   Thanks again for the help and the laugh from your last remark :-)

[soulreaper]

I was wondering if i can use alt hold mode without a gps hooked up?.   I'm not interested in rth at the moment.   Thinking about buying a revo just for alt hold.

[Mateusz]

Altitude hold, Altitude vario on thrust with Complementary YES, it uses baro to maintaing height. Position hold no, that is a flight mode using all sensors including gps, mag and baro. Baros alone normally are accurate +-14cm but they are not very precise meaning rang of +-14cm can go up and down depending on the noise. Noise is average 0.5m on good revo, on bad clone it is way more chech wiki how to fix that if it happens you have bad cappacitor on yours.

Other considerations affecting altitude hold are vibrations, no case or transparent one, bad foam, chech my post above.

[soulreaper]

Thank you. ........

[funtimegrandpa]

I went out today to test things and if flew fairly well.   the alt hold worked good until I started to move around,  then it would change a lot up and down,   I could not fly low because it would one time move up and another down.   Any suggestions?   I am going to still check the things you listed,  but did not know if there was something I could try adjusting awhile

[Mateusz]

Hi,

How about recording raw baro measurements or checking them on scopes via oplink ?

If you have big jumps in baro read-outs it could be wind blowing while you move.

Other things to consider

• Tune vertical PIDs for your copter, maybe default are not good for your build
• Try to reduce vibrations (different mounting/foam tape/accel filtering)

[TheOtherCliff]

simple random higher and lower can be caused by light hitting the tiny rectangular metal baro sensor.  it must be covered so that light can't hit it.

strong quick, random jumps up (I use ALtitude Vario instead of Hold and I am forced to use zero throttle or switch modes) can be caused by not enough foam covering the baro sensor, or even a bad FC placement that always gets wind from props

slow (several to 10's of seconds) rhythmic vertical oscillations can be caused by too much foam (or too tightly compressed) on baro sensor.

[funtimegrandpa]

I am new to the CC3D and Librepilot so if I ask something stupid just guide me so I can learn better.    I am trying to find  oplink  so I can see what is going on.    I did go to the Scopes on LibrePilot but do not see anything for the Barometer   I will post a copy of what I am seeing.  Not sure where to get the screen for the Barometer?

[funtimegrandpa]

Hi,

How about recording raw baro measurements or checking them on scopes via oplink ?

If you have big jumps in baro read-outs it could be wind blowing while you move.

Other things to consider

• Tune vertical PIDs for your copter, maybe default are not good for your build
• Try to reduce vibrations (different mounting/foam tape/accel filtering)

     where do I get oplink

[hwh]

To get the baro scope I usually get rid of the flight time one in the lower right corner.  Do window->edit gadgets mode.  In the header for that scope that appears change scope uptimes to scope barometer.  Then turn off edit gadgets mode if you want.

You can then right click on where it says BaroSensor.Pressure, chose options, and reconfigure it if you want.

You can buy an oplink on eBay, banggood, aliexpress, etc.  They're usually around $20 with shipping.

[funtimegrandpa]

Ok starting to make a little sense now :-)    Here is what I see on the graph now,  does this show anything?    My CC3D does have foam over the sensor and is in a tinted plastic case.   As for air coming in the only area I see this happening is where the Pins connect to the ESC's   

Thanks again for all this help

[hwh]

That's pretty much a normal baro, it's varying less than a meter.   It's about the same as the one on my mini-revo The bad ones jump up and down several meters.

I've never tried it but if you're concerned with wind affecting it you could try blowing across the revo as it's mounted while watching the scope.