kk 2.1.5 trim problem

[llukas11]

Hi,

I built a batbone with kk 2.1.5. I wonder why it is not possible to center trims when in CPPM mode (I got orangeRX and DX9) but when I use separate cable for each channel it works no problem? (zero trims on radio equal to zero position on KK?)

Best regards,
L

edit:
I didnt reflash firmware - I think it is non custom

 

[Craftydan]

Llukas,

Welcome to the forum!

I've played with the ORX615x too, tyring to take advantage of the cppm, but what you're experiencing isn't unique . . . and it's in the RX. I'm not convinced it's an issue across the whole range, but the signal resolution in CPPM mode on that RX simply isn't up to snuff. you can get a full 2056 different widths out of the pwm ports (I haven't measured, but it acts like you can), but at least around center, the step sizes between pulse widths on the CPPM are quite large, leading you to see the sudden jump in trim skipping over center.

If you can ignore the loss of resolution (a matter of how hard you're flying, I suppose) other control boards will allow you to define what the "center" pulsewidth is, although it's rarely a simple task. For the KK2, that would require reassembling the firmware -- doable but just barely.

Otherwise, I'd recommend switching back to the PWM channels, and back to 7 wires

 

[llukas11]

Thanks for quick and torough answer. I guess I'll keep separate wires. I'm just beginning and found that tricopter drifting away during start makes things a bit harder.

 

[Craftydan]

Yup. sure does.

It really is a shame the 615x isn't able to run this feature like it should, but I can see HK cutting corners to make something almost work

Otherwise it's a perfectly nice RX. Perhaps they'll have this working properly in the next version. Not holding my breath, but it would be nice . . .

 

[Balu]

Dan,

how do you measure the CPPM signal resolution? Do you have an oscilloscope? I'm using an 615X on my MWelectroHub build and had some drift issues too. So I finally know what might be causing that...

 

[Craftydan]

um . . . I'm using a very precise measurement setup . . . for input the radio's trim . . . and a kk2's receiver test.

For the RX on the PWM ports, I can generally give a click and a half per point of step on the kk2.
For the RX on the CPPM port, I can generally give a 4-5 clicks per jump, but the jump is 3-4 points on the kk2 (skipping 0, BTW).

No fine measure of precision there, but clearly the step sizes as outputted on the CPPM are far too course.

 

[Basscor]

Related issue perhaps as I am using the mini and 615x. In acro mode it's nice an level, but when I switch to auto-level it wants to drift to one side. If I trim for auto level, acro has a drifting problem. There is an option in the self level settings for Acc trim but it doesn't seem to have any effect. Thoughts?

 

[Craftydan]

Bascor,

Trim your radio to neutral and set the radio limits to get ±100 in the Receiver tests and leave your radio settings alone.

With those settings the acro mode should be neutral, then you need to tell the board what "level" is by running the ACC cal . . . but often your landing skids aren't level with your props, so you still need to trim -- do that in the board, NOT the radio.

For the kk2 boards, there are pitch/roll trims on the self level settings nudge those around until the quad holds a good level -- keep in mind it will still drift with the wind, but when the self level is trimmed it should drift the same amount in the same direction (downwind) regardless of the direction it's pointed. if you yaw 20 degrees and the drift changes course, you've still got a touch of trimming to do.

Once both your radio trim zeros out in the receiver tests and the accelerometer trims are set, you should be able to seamlessly transition between the two modes.

 

[Basscor]

Hey Dan

I had done as you said with the receiver test as in David's tricopter setup vid (I am running his V3 kit). With everything zeroed out and showing +- 100 for everything, acro mode is nice and stable without a tend to drift left, self-level not so much

I was doing my maiden and testing inside a gym, so no wind in there. I did rerun the ACC calibration at the location, but no dice. Looked at the selflevel settings and there is the acc trim for roll, but I went +- 20 and neither direction seemed to correct the problem.

Should I just prop up the front left side and then run the ACC calibration again?

 

[Craftydan]

That might be what you need to do. I've never had to add more than 5 or so points to either axis, but that's not to say it isn't normal for your board -- again the quality of your cal all depends on how level your skids are with your props, which really is unimportant other than the cal.

BTW, what ROM are you using? That might also make a big difference.

 

[Basscor]

I am running the Steveis 1.19s1 on the KK2.1.5 mini

 

[Craftydan]

Good. ROM shouldn't be an issue then.

when you get ready to re-cal, take a quick hover and see which direction it's drifting -- that's the side/corner you need to prop up a bit.