Rotorflight Tips

December 1, 2024

I've run into more than a few problems while learning to use Rotorflight. It's honestly not the easiest thing to figure out for someone just getting into helicopters, especially if you're coming from something like the Goosky S2 that already has the flight controller set up. With this in mind I figured I'd set up a collection of hopefully useful but, at the very least, somewhat interesting tidbits that should make your Rotorflight experience a bit smoother.

Swash and Tail Correction

When setting up the Servos inside the "Servo" tab, it should be stated that you must only set the centers and limits of the servos. Do not attempt to correct swash setup or tail pitch within this menu. Those should be adjusted inside the "Mixer" tab. There is a dedicated swash correction and tail trim centering within the mixer tab. Also, check out this video for valuable information about yaw calibration in the "tail geometry" section. Actually, just check out all the Nexus videos from RC Video Reivews channel.

One really great tip in that video is how to check the tail servo is moving the correct direction. To do this, you set the tail blades vertical, then fold the top tail blade 90 degrees toward the helicopter canopy. Inside the "Mixer" tab, enable the over-ride and adjust the yaw a few degrees clockwise. If the tail servo is moving in the correct direction, the tail blade will point right when viewing the helicopter from the top down with the canopy facing forward.

Hobbywing Platinum 150A ESC Hookup

When using the Hobbywing Platinum 150A V5 with the Nexus, you will need to attach the leads as follows:

Brown, Red, Yellow (Listed as R + - on the case) --> RPM Port
Black, Red, White (Listed as S + - on the case) --> ESC Port
Yellow (Marked as ⎍ on the case [next to - + ]) --> SBUS

The designations are found next to the wires on the back of the case.

You'll need to adjust the SBUS port in Rotorflight Configurator for ESC Telemetry. This can be found in the "Configuration" tab.

Alternatively, you can just change the connector and plug into one of the available A, B or C ports. It's also worth noting that if you follow my instructions for adding a backup capacitor pack, you will lose access to the SBUS option in the serial port menu of the configuration tab. If you're using a different size hobbywing ESC and don't have a lead for telemetry, you can carry a lead out from the pulse output of the programming port on the ESC and take it back to the flybarless instead. That would be the port marked P + - or ⎍ + - .

Adjusting ESC PWM Parameters

When setting up the Motor there are some PWM settings available. The presets are 1000 for throttle stop, 1070 for 0%, and 2000 for 100%. I've found some videos online that state the 0% should be 1010, but one of them stated to play with that value until you get the motor to just turn on using motor override set to 5%. That video also stated that on Hobbywing ESC's a value of 1033 seems to work well. This did not work for me. I found that I needed a value of 1368 before the motor would start at 5%. Also worth noting that even though the motor gets started at 5%, it still turns it up to 1157 RPM. I'm not sure why that is, but I can say that with these settings the Helicopter soft starts very well and I set the governor to 1000 RPM to make sure that my motor wasn't somehow being turned up with that 1170 PWM value. It maintained 1000 RPM just fine. (Solved Below)

After some time fiddling around with settings, I've found that the reason I couldn't get the helicopter to start at 5% with the above mentioned settings was because the ESC was in ELF Governor mode. It clearly stated in the instructions for the Hobbywing ESC's that the ELF Governor requires that the throttle be higher than 40% before the motor will start. DOH! Switching to External Governor mode corrects this issue. In my defense, I was using a stock Goosky RS4 ESC, which, to the best of my knowledge, does not have an interface to adjust these settings. Either way, this is a step in the right direction to properly tune the helicopter.

One more note, once the ESC was changed to External Governor mode I adjusted the PWM values to those stated in the manual, defaults being 1100μs - 1940μs and everything starts perfect. I believe this also explains why the helicopter RPM would overshoot when starting up, then come back down to the proper setting.

Nexus Orientation

The Nexus unit is intended to be installed with the servo connection pins facing the canopy of the helicopter. If you intend to orient the unit differently, this can be done inside the "Configuration" tab under the "Board and Sensor Alignment" setup. Something that's a little confusing when you look at your options is that you'll see one that says First GYRO with an option for setting the direction. I think that when the Nexus is plugged in it probably populates that field so the configurator knows that the gyro inside the Nexus unit is turned clockwise 90 degrees since the configurator works with many different modules. Apparently, the proper way to change the orientation of the entire unit is by adjusting the roll, pitch, and yaw degrees to match the direction you decide to turn your unit.

Rotorflight Configurator 2.1.0 takes care of this rotation misunderstanding by completely eliminating the option to change physical gyro position.

Calculating Transmission Gearing

The stock transmission gear ratios are the same in the Kraken 580 as they are in a Raw 580, but a useful interactive guide for figuring out transmission ratios can be found here. Make a copy of the spreadsheet and follow the directions to use it. I added the Kraken 580 to the list using the stock gearing found in the manual. This can be done by adding the data using their data sheet tab found at the bottom of the spreadsheet.

Elevator and Collective Adjustments

When adjusting the servos use the reverse sliders to make sure that the servos are moving in the correct direction, but don't attempt to correct elevator and collective directions. The elevator and collective reversal needs to be done inside of the "Mixer" tab. In the picture shown you'll see that on my Kraken 580 I had to reverse the elevator control for proper swash movement.

Gyro Filters

The "Main Rotor Minimum Filtered RPM" should be set to 200 RPM lower than the minimum RPM you ever plan on running. Mine is currently set lower than it should be. It's important that the filters are not too wide because this will slow the flight controller processing down, causing sluggish reactions.

Governor Debugging

If you're going to use the Nexus unit as a governor you may need to enable a few more features in the blackbox settings. When I was going through Rotorflight's guide on tuning the governor I couldn't figure out why their examples had different options shown for data viewing. I missed this very important part; in the debug options under blackbox settings, you need to select "GOVERNOR" in order to see the Rotorflight example data. I also selected "THROTTLE" because it seemed logical, but there are some other options available you may want to play around with.

It's very important that if you choose to use the flybarless unit as a governor you also remember to change your ESC governor settings. I think most hobbywing units come preset with ELF* Governor enabled and this needs to be changed to External Governor mode with PWM range settings at 1100μs - 1940μs. This will prevent problems with the motor starting at low values, but you will still need to start the motor with at least 6% throttle before it turns over, even in External Governor mode.

*I contacted Hobbywing tech support about this "ELF" Governor term. They tell me it's not actually an acronym, but a translation from Mandarin. I believe that it's not supposed to be taken as a little elf creature operating the governor, but instead the Mandarin term for "clever" or "smart", which is very similar to the word elf. It's just been a little lost in translation.

If you're having issues with the resolution on your receiver while using DSMX protocol, you can enable "extended throws" inside the radiomaster radio to help improve your resolution.

PID Tuning by Bert Kammerer and "..."

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