Taranis X8R SBus to PixHawk- Throttle problems

ArduCopter Copter 3.1
1

Hi

I had my PixHawk on a DJIF550 Hexa Frame with the new DJI E300 propulsion kit, controlled with a Spektrum DX9 and a HobbyKing R800x receiver that has SBus out connected to the PixHawk RC-IN port, and was working ok, after some tweaks.

Radio calibration on all channels had the range between 1088 and 1940.
The ESC’s from the DJI E300 kit are optocoupled and don’t support calibration.

The arming procedure of the PixHawk, that made the props rotate after arming was working ok with MOT_SPIN_ARMED of 130, but I had to tweak the RC_IN MIN of the Throttle to 1122 to have a smooth rotation on idle after arming.

I swapped the Radio Control system to a Taranis X9D + X8R receiver because the extra channels PWM could be hooked directly to a 3 axis gimbal.

The X8R receiver was set to Mode 4, i.e. 16 channels output with the last 8 exposed on the receiver PWM pins, and was connected to the PixHawk via the SBus to RC_IN same as before.

I redid the Radio Calibration and on all the first 8 channels the range is between 982 and 2006. The last 8 channels are also ok and control the gimbal perfectly (output range also between 982 and 2006).

This brought some issues with the arming procedure on the PixHawk. Now when I arm the PixHawk the props won’t spin, and I have to move the throttle until it reaches +/- 1150 value to have the props spinning.

So now my throttle was a small “dead zone” at the bottom where the props won’t spin, i.e. I arm the PixHawk, no props spin, raise the throttle and props start to spin at 1150, and increase normally until max speed, when lowering the Throttle the props STOP around 1150 down to the 982 lower value of the throttle value.

I’ve already messed with MOT_SPIN_ARMED from 0 up to the max of 270 with no solution.

I also looked at THR_MIN but besides not understanding from what the percentage is referring to (percent of what) and no matter what I use on the allowable range nothing changes on the behavior above.

Anyone has any tips on how to have the motors spinning at the current minimum throttle? I’m sure others here also use the Taranis+X8R+Pixhawk combo but not many with the E300 propulsion kit, but your inputs are welcome.

TIA

Luis

2

I managed to get a solution with the help of DJI

The E300 ESC’s have a range of 1120 to 1920.

The solution in this case is to set the Throttle channel limits on the radio, so that the PixHawk sends 1120 at minimum and 1920 at max throttle.

One can accomplish this using the RC Calibrate screen to check the output values, while changing the limits on your radio.

After this step, perform a standard radio calibration, and problem solved.

rgds

Luis

3

Brilliant thanks, this solved the mystery for me too as to why the E300 didn’t spin after arming, and why there was a deadband at the bottom of the throttle. Thanks!

I find the throttle mid position is around 700-720 which seems pretty high, do y’all see the same thing?

4

BTW as a newbie I love the E300 - it’s a nice balanced set of props/motors/ESCs at a pretty reasonable price, and like the self-tightening props (and as they’re exactly the same as the phantom props easy to get replacements for).

They also seem to be really efficient - I get 25min hover time out of my bog standard F450/E300 quad on a 3S 5000mah Zippy lipo using the standard 9443 props, which seems to be in a different league to the likes of the Iris.