[daveapplemotors]

Today I should receive my long awaited Revo Nano and a GPS module from BG. I am excited because I have been trying to get one since last summer.
 
If the hardware fits a 250 heli I will learn altitude control, way point navigation, auto take off / landing, etc.

I wonder how much this will cost me? Wish me luck...

[TheOtherCliff]

You seem to already have a good grasp for setting up a heli. 

Given that, the GPS stuff is quite doable.  Twist your high current power wire pairs/triples, battery to ESC, ESC to motor.

Always have Attitude mode on your flight switch, take off and land with it.  If there is a problem in the air, you can always switch to it.

Get it flying in Attitude mode first (same as CC3D), then change the Attitude Estimation Algorithm to INS13 and fly again, then add a flight mode with AltitudeVario throttle mode to test the baro, then add GPS and add a VelocityRoam flight mode.  At that point, you have GPS flight mode working and you can branch out from there to waypoint, etc.

[daveapplemotors]

Revo Nano came last night. Setup includes 'nose down and right side west' or 'left side down and nose south' for the magnetometer and / or accelerometer sections.

Thanks theothercliff for the note about emissions from my power wires. I will braid my ESC / motor wires

Since I didn't have the Revo installed into my heli yet I propped the unit on books and things to calibrate. It was probably positioned more accurately for each orientation than it will be in the heli. And I will redo calibrations to be accurate now the Revo is installed.

My board is not level when my heli is sitting on the skids and the mainshaft is not perpendicular to the heli base even if the skids were perfect. But the Revo board is perpendicular to the mainshaft and aligned well longitudinally.

questions:

Is it necessary to be as accurate as possible for all calibration orientations? Should I make a jig to hold the heli level and at right angles? I should calibrate based on orientation of the helicopter's mainshaft, que no?

What is the temperature compensation for?  It failed to calibrate 3 times because it didn't vary 10 deg . It was about 15 degrees where I was and it reported nearly 30 degrees after a while. What causes the temperature change? Is it heated electrically?

Thanks,
Dave

[f5soh]

I have recently added some pages to Wiki, take a look here:
https://librepilot.atlassian.net/wiki/display/LPDOC/Sensor+calibration

Accel calibration is done without frame, it calibrate every axis for bias and scale assuming the gravity is 9.81

[TheOtherCliff]

The angles for calibration aren't super critical.  I just eyeball it.

When it says stationary though, it must be completely still.

When you are doing the thermal calibration it also needs to be still.  To get a good range that covers winter and summer, I:
- plug usb cable into just FC
- put FC in a sealed baggie in the freezer for 10 minutes, gets it down close to freezing.
- take it out of the freezer (leave baggie on till done) and immediately put it in a shoe box or similar on top of a hot light bulb
- immediately plug it into computer and start thermal calibration
- don't let it get over 70C, switch off light bulb way before that

When flying a true heli, the rotor won't even be level in stationary hover, you will probably want to adjust the rotate virtual roll a few degrees for that.

[daveapplemotors]

I spend a lot of time adjusting, checking and test flying each helicopter so that with all three axes in "Rate" it's happy to hover a while hands-off.  And I understand that eyeballing my three axes will get it flying pretty well because people are really good at eyeballing 90 degree. Furthermore the geometry of 88 or 89 degrees is very near 90 for our applications.

But, I want precision a little more so I will work on a "Device For More Precise Orientation During Setup" a bit which will be probably a wooden or cardboard box, some tape and a line on the field The "Aim the nose north" part is worth drawing a line anyway, que no? 

Thermal Calibration: baggie in the freezer and then into a bowl of hot water at 69 degrees. Foolproof with saucer holding the important part of the baggie under water. Thanks, theothercliff, for the how-to which probably should go into the wiki verbatum.   

And I must learn how much battery that first flight can use flying after it spends 20 minutes finding satellites.

[f5soh]

The angles no need to be perfect while calibrating Accelerometers, if board is 88° instead of 90° the error is very small.
On six positions he try to adjust bias and scale assuming the gravity is 9.81

In practice, a board with a case and a box to maintain board perfectly still and vertical at some steps.

For thermal calibration no need 70°C max.
As an example, initial compensation from baro manufacturer only applies below 20°C. Assuming the sensor response is linear above 20°C.
Water is not a good idea because the pressure inside bag should change, not good for baro sensor (air temperature, water pressure)

[daveapplemotors]

Weird problem:
If the tail servo is plugged in when I connect flight battery none the servos work. Disconnect the tail servo and the cyclics function then re-connect the tail servo and everything works. I will try another tail servo when I get time--maybe the E Flite DS76t again!** And maybe I get time to test fly this weekend but the weather report looks lousy. Note to self: shorten 13 wires to tidy up.

This Revolution Mini from BG doesn't have regular 3 pin outputs to servos. There is an 8-wire plug for outputs. I don't think it is possible to specify it in "Configuration " because it is default. The 8 output wires: red is + pos, black is ground; green = ESC ; White, Blue & Yellow are cyclics (1-3); gray is for the tail. Orange is unused so far.  You must distribute power to the servos because they each need pos and neg. I used a couple of headers with the pins soldered together. (see photo on Google drive https://drive.google.com/drive/folders/0B5McJ3wwtyLxMnpDZHJ0NEtPYW8).

It acquired 7 satellites while at my kitchen table last night! Can't wait to fly!

**I tried this DS76t before but it overheated even when I lowered input frequency to 50.

[daveapplemotors]

Weird Problem:

with USB:
If the USB is connected before or after flight battery then the servos work. If the USB is then disconnected afterwards they continue to work.

without USB:
If the heli is powered up without the USB cable connected the servos don't work unless the tail servo is disconnected when powering up then cyclics work and then reconnect the tail and everything works.

Any ideas?

[f5soh]

Check your +5v source.
Maybe there is a current spike with all servo connected, especially with your tail servo ?

[daveapplemotors]

“From theOtherCliff:
Always have Attitude mode on your flight switch, take off and land with it.  If there is a problem in the air, you can always switch to it.”
Got it Attitude Mode is easy. I have my DX7s set for 6 flight modes.

“Get it flying in Attitude mode first (same as CC3D), then change the Attitude Estimation Algorithm to
INS13”
Got it change in (System / RevoSettings / BaroTempCorrectionExtent / FusionAlgorithm)

“ and fly again, then add a flight mode with AltitudeVario throttle mode to test the baro,”

****EDIT
OK I found “Altitude Vario” and I notice it's linked to collective and that any setting will be in all three Settings Banks.
**That brings up two questions.
How do I invoke “Altitude Vario”? 
Is this just to test baro because I notice that it will be same for all three settings banks?

 “then add GPS”
More than in Configuration / Harware ?

“and add a VelocityRoam flight mode.”
Got it -- Configuration / Input / Flight Mode Switch Settings
 
 “At that point, you have GPS flight mode working and you can branch out from there to waypoint, etc.”
Thanks.

[daveapplemotors]

One step forward and ..
The servo problem cured by tining the connector pins with a little solder.

In preparation for autonomous flight I set a flight mode for "Attitude". With the heli on the bench and motor dis-armed the swash jumps about 20 degrees to the right going into "Attitude". That will crash. It jumps back when it is switched back into another mode.

I tried "Attitude" mode once on the CC3D board and very nearly crashed. I had to get out of "Attitude" mode quickly.
The other flight modes don't move the swash.

Anyone every fly a heli in "Attitude" mode?

[f5soh]

About attitude, check how is the PFD when level.
Bank the heli and see if PFD horizon react fine.

In flight: Take care about vibrations (Attitude state can be totally wrong due to vibrations), try a little fly in rate or manual mode almost level and check your PFD. You can log your flight: Tools > Record..

[daveapplemotors]

G'day Laurent,

You are right on, thank you.

Redoing all the calibrations helps. Now the swash jumps aft a tiny bit when I engage "Attitude". When I get to the field I will calibrate again so that jump will probably disappear. But now I must wait for 30 cm of snow to melt.

About balancing:
I use Audacity software and an old earbud to balance all my helicopters including Blade nano tail rotors.

be well,
Dave

[daveapplemotors]

Good weather yesterday. I tried to move my home position to the center of the soccer pitch instead of a sidewalk near some trees.

EDIT: I don't know how to move home position, Can anyone help me with this?  --I got this.

On another note it appears the PIDs are treated differently in LP than they were in OP. I had to drastically reduce settings--notably pitch--on tow of the 250s. Settings that were smooth in OP make a bucking bronco in LP.