Quanum Nova (CX-20) with APM FC - Pilot Tips

In this post, I thought I would summarize some important tips. I will add them here (as they come up) if they don't seem to fit anywhere else. But in general, be sure to use top Blog Search.

Arming Tips:
Arming in Loiter, and then switching to Stabilize before take-off is best. If Arming in Loiter, HDOP (GPS quality) must be 2.0 or better or it will not Arm. So give it (up to) 5 minutes before first Arming attempt. Just because you get a get GPS 3D-Fix (7 or more satellites, so green led steady-on) doesn't mean HDOP is good enough (actually, lower is better). First flight of day will take the longest (as gps-almanac is updated). Otherwise, as a test ... you can Arm in Stabilize. I still recommend at least a 3D-Fix (green led steady-on ) but HDOP is not checked. Therefore, do not utilize GPS dependent flight modes during that flight (including Loiter or RTL). Also, GPS doesn't really work indoors.

Arming Trouble:
- Check that TX radio itself and FC radio inputs are properly calibrated (center stick trims first).
- Be sure no TX radio Inputs are reversed. Also, that Throttle goes down when stick is down.
- In MissionPlanner/FailSafe, be sure correct radio sticks are correctly assigned (ie for Mode-2 Throttle and Rudder/Yaw are on left stick gimbal.
- In MissionPlanner/FailSafe, be sure correct radio sticks respond and in gradual and linear fashion.
- Normally, MissionPlanner's main-screen HUD will show the Pre-Arm error. Repair sub-system in error.
- Try Arming Motors in APM Stabilize mode ( aka CX-20 "Manual" mode). It requires no GPS-Fix.
- Try disabling GeoFence (if you have used the MissionPlanner Setup Wizard lately, it might be on). If it's ON, you must have a GPS 3D-Fix (even in Stabilize). So basically, you can only Arm Motors outdoors.

Confusing Cheerson Flight-Mode Names:

True APM Modes and comparable (Nova-CX20 Mode):
Stabilize (Manual)
Loiter (Stable)
Simple (Direction Locked)
Altitude Hold (Altitude Hold)
RTL (Return To Home)
-   In my docs, I always use the true APM flight-mode-names.

Stock-white Radio Note (using confusing Mode-names from Nova/CX20 Owner's Manual): If you are having trouble Arming quad, here is a summary: If you have GPS-3D Lock (solid green light) AND hdop <= 2.0, you can (and should) Arm in Stable switch mode. Then, switch to Manual mode and take-off. Otherwise, you can just Arm in Manual mode ... but don't expect RTH (pilot invoked or emergency) to work during that flight. Also, don't switch to and try to use any GPS dependent modes like Stable during that flight.

GPS Operation (in layman's terms):
I think 6-7 sats is minimum to get a basic GPS-Fix (Nova's green rear-led on steady). HDOP is one way to measure quality of that fix. To Arm in Loiter, you need a hdop of 2.0 or lower/better. IIRC, what Dkemxr said ... the stock GPS module's resolution is 2.5 meters. So hdop of 2.0 is 2.5m * 2.0 = 5.0meters (15 feet). So, anything GPS dependent (Loiter, RTL) can have a 5 meter location variance and still be within acceptable limits. You can see why lower hdop is always better. As for hdop definition, Google is your friend. Main thing to remember is H stands for "Horizontal" or location "across" the earth (not altitude). I'm no expert, and this is just my very basic understanding of how it works.

The compass plays an important role in GPS navigation.  In "GPS Dependent Flight Modes" like Loiter, PosHold, or RTL, the APM Flight-Controller calculates a desired lat/lon position, compares it to the current lat/lon position, and then lastly uses the compass to know which direction to go to get there.
If the compass is "off a little" the new position will be off, so the process will repeat resulting in a circling hover (aka "toilet-bowling" or "toilet-bowl effect"). A good/clean/accurate/proper compass calibration is the fix. Any time the compass mount is disturbed or changed, a new compass calibration is again necessary.

Mission Planner basics:

• Install Mission Planner for Windows (download)
• The APM Flight-Controller/ Arduino drivers for Windows will also install.
• You will see drivers load either now, or when you later connect USB cable
• Connect Nova's LiPo battery
• Connect USB cord to laptop. Listen for Windows "new USB Device Connected" chime
• Be sure you are using a real USB cable and not just a cell-phone "charging-only" cable.
• If Windows can not detect Nova's "Arduino Mega 2560" Flight-Controller, Mission-Planner will surely not be able to either. Fix this problem first (should look similar to image below, but COM port number might be slightly different).
• If it won't detect using Nova's lower (Mini-USB) external port, open Nova shell and connect USB cable directly into side of Flight-Controller (a Micro-USB). Be sure it fits thru white FC case to seat completely.
• Still having detection problems? Use a known good/tested short USB cable. Connect to real USB-port on back of computer (no hubs or extensions). Try a USB-2.0 port. 
• Press Reset button on FC before connecting to USB port.
• Be sure external yellow/amber LED on Nova is not flashing (signifies FC is in a self-induced calibration mode).
• Start MissionPlanner. Set comm-port to Auto and then click "Connect" button (top-right)
• Ignore prompts to upgrade firmware unless you know what you are doing and what you are getting yourself into.
• The shipped (CX-20 custom) version of ArduCopter v3.1.2 works fine for initial flights.
• When finished, click "Disconnect" in MP before disconnecting USB cord.
• NEVER disconnect USB cord while MP is connected-to and communicating-with FlightController (it has been known to corrupt FC firmware).
• Shutdown MP
• Disconnect USB cord (this order prevents triggering Nova's LowVoltageWarning).
• Disconnect Nova's LiPo battery

Analyzing Logs:
While I used to log more items, I'm now backing down to Default+IMU. LOG_BITMASK,958 which is ATTITUDE_MED GPS PM CTUN NTUN IMU CMD CURRENT (the basics plus vibrations). See this page for help using logs.

Simplified Full Nova/CX-20 Setup:
A simplified version of this. While I don't have a stock-white-radio set, this should work for those setups. Could be used as a basic build-up (with default parameters), just to make sure quad hardware is functional and core FC software is working. This is not meant to be a "final" config ... just a simple-flyable one.

• Start with base quadcopter, with no payload or optional equipment.
• Check all wiring for good connections at connectors and soldering points.
• Remove propellers and use (known good) fully-charged 11.1v-3s LiPo battery
• DO NOT upgrade firmware on a new Nova/CX20. The version installed from factory is fully functional. If you must do it, see "Firmware Upgrades" section below.
• Press Reset button on top of FlightController to MasterReset it before starting. Give it time to reboot.
• Attach USB cable to bottom of quad and secure to landing-gear so it doesn't accidentally become unplugged. Windows should detect USB device.
• In MissionPlanner, select Auto com-port and click Connect.
• In Parameters Full List, click "Reset to Default" button
• Do all "Mandatory Hardware" calibrations in MP
• Radio first, then all the other hardware devices.
• Click Write parameters and wait 20 seconds
• Calibrate ESCs (outside of MP). Test motors.
• For RTF models, this can probably be skipped for now. PnF/BnF models likely need it done at least once in it's ESC's lives.
• Test FailSafe
• Click Write parameters and wait 20 seconds
• Backup Parameters (They are Defaults with current Calibration data).
• Install propellers (in proper way) and bolt-on tight. Also install all body screws.
• Carefully do "Holding by Landing Gear" test and verify Throttle, Pitch, Roll, and Yaw.
• Take outside to grass field with light or no wind. Stand safe distance behind quad. Get GPS-3D fix.
• Arm in Loiter, but take-off in Stabilize. Give it plenty of throttle (60% ?) to get into the air. Try to hover 6ft off of ground.
• Please note that your ANGLE_MAX parameter might be set rather high by Default. This will allow quad to save-itself in an emergency RTL/RTH situation (including in stronger winds at higher altitudes). So, "take it easy on the sticks" and use caution when pushing them toward full gimbal travel.
• I use ANGLE_MAX,3000 (my Parameter edits)

Initial Quad Setup Trouble:

• First Flight with ArduCopter
• After a hard landing ... while sitting on level desk, Mission Planner main-HUD shows Nova NOT to be level.
• Open quad and verify Flight Controller is still mounted properly (level and perpendicular to front of Nova).
• Re-calibrate Accelerometer (includes gyro).
• Nova (or CX-20) orbits in a small circle or "toilet-bowls" or while Loitering
• Note: Loitering depends on all instrumentation sub-systems
• To Loiter properly, Nova needs a GPS-Fix (preferably with a good hdop)
• Calibrate Compass
• Calibrate Accelerometer
• Barometer (Altimeter) calibrates itself on power-up
• All ESCs are beeping
• ESCs are getting main (hard-wired) run voltage from main LiPo battery, but ESCs can tell they have no PWM control (control signal that tells them to stay Off or stop, Arm motors and start them, speed-control, etc.)
• Check in this order
• This can be caused by no BEC (+5v) voltage being connected to RX radio (and therefore, also no power being passed to FlightController).
• FC might not be getting power (usually via CH-1 Aileron connection)
• FC can tell that Radio-Calibration has not been completed.
• FC might be damaged or malfunctioning
• FC might have a corrupted firmware and needs to be reset and Firmware re-loaded with MissionPlanner.
• Followed by loading of Default params & complete calibration.
• All of a sudden, MissionPlanner for Windows can not connect to Nova quad any more.
• Remove the body shell.
• Unplug the quad's USB extension cable from side of FlightController.
• Use a slightly different cable. Plug your spare Micro-USB cable directly into the Flight Controller and then directly to laptop.
• If this works, the quad's built-in USB extension-cable might be bad.
• See "Mission Planner basics" above.

Firmware Upgrades:
DO NOT upgrade firmware on a new Nova/CX20. The version installed from factory is fully functional (even the Uart port for 3DR Telemetry radio works). If you expect your firmware is corrupt (unlikely) or would like to go-back a version, you can use MissionPlanner to load desired AuduCopter version (non-beta). If you need "Terminal" to aid in Troubleshooting, load ArduCopter v3.1.2 or AC315 (v3.1.5). After hardware passes, you can always load a newer version.

• Start with base quadcopter, with no payload or optional equipment.
• Check all wiring for good connections at connectors and soldering points.
• Remove propellers and use (known good) fully-charged 11.1v-3s LiPo battery
• Press Reset button on top of FlightController to MasterReset it before loading a different firmware.
• Connect USB cable to Windows
• If you want to backup your Parameters, now is the time.
• Start MissionPlanner but do not click "Connect" button.
• Upgrade firmware to desired version from "Initial Setup" screen
• You can load current ArduCopter v3.2.1 Quad (no Telemetry on this FC)
• You can click "Load Custom Firmware" and load custom v3.1.5, 3.2 or 3.2.1
• Once you select the file, the upgrade will start. You will not get a chance to abort or cancel.
• The Firmware will Load, and then Verify.
• The read red-led is off. The green-led flickers quickly
• When Done, light go back to normal
• You can click "Pick Previous Firmware"
• Select one with AC at the end. For example, you might want AC315 
• Follow all prompts and directions
• Don't be in a hurry. Don't let USB cable become unplugged.
• Now that firmware is installed, press Reset button on top of FlightController to MasterReset it one last time.

Battery Tips:
I use a Turnigy 11.1v 2700mah 3s 20-30c LiPo (102x35x28mm). I have 2 identical ones that I rotate. They usually take-in around 2700ma again, but I've seen them both take-in as much as 2800ma before. Not sure about all LiPos, but these are obviously rated 2700ma between their useable range of 9.0v-12.6v. If you take-into-account that they hold more like 2800 ... rated 2700ma between their (safer) useable range of 10.0v-12.6v.

I Balance Change at 1C (2.7amps) and it takes about 90 mins. My AccuCell-6 Charger also has a Discharge setting. I never use it, but I did test it the other day. It's voltage limit is not adjustable (only by cell count). It always discharges to 3.00volts per cell. Contrary to forum reports, I think it's highly unlikely that draining to this level damages LiPos. And think about it ... that's less than 20% of rated 3.7v cell voltage. I tried it ... took 3S down to 9.0volts. You guessed it ... no damage, fire or LiPo explosion. Not sure where pilots get some of these crazy misconceptions.

Also tested/observed ... when starting to charge my 3S-2700 back up from 9.0v, it gets back to 10.5 volts after only taking in about 25ma.

To apply Ohms Law ... Power (watts) = Volts * Amps.
So, as Volts goes down, you can still reach your required Power target if you have sufficient Amps (to make-up for it). Pretty sure that is where the High-C or Current ability comes into play. Battery must be able to deliver increased current toward the end of the flight.

I also have a Predator 2200mAh that works fine, but I only use it while Nova is on workbench or office (getting logs, params, etc.). This way, my 2 main 2700's are always fully charged and ready when I get to the field.

The Nova is currently 1002g (All-Up-Weight with Mobius and battery). I am getting 11-12 minutes on each 2700mah battery. The first single-beep LowVoltageAlarm first sounds around 10.9v. A minute or so later, the continuous beeping/flashing LVA happens at 10.6v (and I'm already landing at this point). According to forum reports, the Nova's LVA is sometimes inaccurate, but seems to be working fine for me so far. This will have to do until I wire-up a Power-Module to Telemetry. I also use a count-down Timer on the Taranis.