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Bidirectional DSHOT #3

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bkleiner opened this issue Mar 12, 2020 · 24 comments
Open

Bidirectional DSHOT #3

bkleiner opened this issue Mar 12, 2020 · 24 comments

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@bkleiner
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Hi,
Is there a chance that bidirectional dshot will be supported eventually?
Really like the hardware so far 👍

@IB1387
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IB1387 commented Apr 12, 2020

Bump. The only thing missing from this is support for RPM filtering. :-)

@speurhond
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RPM filtering would be great

@wuzle
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wuzle commented Jul 27, 2020

I agree. It would not have to be bidirectional DShot though, it could also be implemented into Betaflight. While I don't have any clue on how much work it actually is to make Betaflight OneWire compatible, in my opinion the update speed should be enough to provide a 8kHz PID-Loop with sufficient RPM-data.

In general I have not flown an ESC that so finely controls motors like the Fettec 35A. It really makes a big difference on tight lines and difficult tracks. This weekend I had the chance to directly compare two identical setups (one Singularitum with a Fettec35A V1.0 and another with that 20x20 Hobbywing BLHeli32) on our training track and the difference is quite stunning. The Fettec runs way smoother all around and provides way more control especially on the lower side of the throttle curve and upps the efficiency quite a bit. The only thing missing is the RPM-Filter. With that enabled you'd have no vibration leaking into the gyro data whatsoever with minimal filter latencies and I can't imagine that there is anything comparable on the market at the moment.
Right now, the Fettec ESC is slightly above my BLHElis32 in noise profiles, RPM-Filters would -I guess- catapult it way ahead.

@stackola
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stackola commented Aug 6, 2020

Bump

Can we get any update from the author on this?

@lichtl
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lichtl commented Oct 17, 2020

There is no plan to implement bidirectional DSHOT. The best is if Betaflight would directly support the Onewire protocol (which then would allow to get all telemetry data in real time (voltage/current/rpm).

@stackola
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stackola commented Oct 18, 2020

Are you guys working on getting Onewire into BTFL, or do you just hope someone from BTFL will do it them self?

@wuzle
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wuzle commented Oct 19, 2020

I guess Onewire integration into Betaflight would be even better. In the end for the consumer it doesn't really matter where the juice comes from :)

There is also additional functionalities like Battery compensation features that we could enable when there's fast enough telemetry data (normal telemetry is not fast enough)

@bkleiner
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Author

There is no plan to implement bidirectional DSHOT. The best is if Betaflight would directly support the Onewire protocol (which then would allow to get all telemetry data in real time (voltage/current/rpm).

Is there a specification document for OneWire (i guess its "just" serial?) to get the ball rolling on this.

@rauar
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rauar commented Oct 20, 2020

There's a (probably very old) document on rcgroups - unclear how much it fits the current onewire implementation on fettec escs: https://www.rcgroups.com/forums/showatt.php?attachmentid=8524039&d=1450424877

It mentions a PWM-based trigger to receive telemetry...

@lichtl: Would be great if the fettec devs could share some specs so that there's a chance to get it implemented in Betaflight. Currently stuck without RPM filter using a Betaflight FC and a Fettec 4in1 😖

@lichtl
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lichtl commented Oct 21, 2020

Hi @rauar

please find attached 2 implementations (one for Arduino and the one used in KISS FC firmware). They do contain some documentation as well. Hope this helps for the start.

FETtecOneWire.zip
FEttecESC_arduino.zip

@stackola
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@lichtl Are you guys actively working on getting this into BTFL, or are you just hoping and waiting for some community member to get around to that?

@rauar
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rauar commented Oct 25, 2020

@lichtl thanks a lot for the files. will check them out as soon as i find some spare time.

@stackola check out this betaflight issue - i tried to reactive the discussion on a former request and the betaflight and blheli devs plus Felix from Fettec were commenting: betaflight/betaflight#7264 (comment)

Unfortunately I seems like there are 2 ways how to implement this and there's no agreement yet on one of those options. One option is to implement it in DSHOT on the signal line (like BLHeli) and Mike prefers this (avoid multiple implementations of the same "thing") and Felix seems to promote Oneshot (using a dedicated telemetry wire).

Not sure if they will agree on one of those options (I doubt it atm) - but I see the points of both sides.

I think the more people ask for support for RPM filtering when using Kiss/Fettec ESCs the higher the chances they come to an agreement.

@Linjieqiang
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@rauar Any news?

@Linjieqiang
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@ronlix Any docs about the Fettec Onewire?

@stackola
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It's been almost a year since you have claimed to be going into testing. @FETtec

Can your customers ever expect to get working RPM filters on betaflight or not?

@krunked-fpv
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krunked-fpv commented Mar 21, 2021 via email

@stackola
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stackola commented May 26, 2021

Bruh. Lol. Give it up.

No!

Bump.
Give me bidrectional dshot!!!

@stackola
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Any day now!

@krunked-fpv
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krunked-fpv commented Jun 29, 2021 via email

@VolkerGoeschl
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Never gonna give you up, never gonna let you down, never gonna run around to D-shot!

@stackola
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Never gonna give you up, never gonna let you down, never gonna run around to D-shot!

Found a fix: Sold my Fettec stuff and won't be buying any more.

@homepods
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homepods commented Nov 8, 2023

with or without bidirectional dshot - does it matter? perhaps no. if you test side by side BF with rpm filtering/bidi shot and FT would you see a big difference or any difference at all?

@stackola
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stackola commented Nov 9, 2023

@homepods It matters a lot. AFAIK, FT also uses some bidirectional protocol but it's homebrew and not compatible with BF.

@homepods
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@homepods It matters a lot. AFAIK, FT also uses some bidirectional protocol but it's homebrew and not compatible with BF.

As I understand FT reads through the TLM the motor rpm and does the filtering accordingly.

  • BLheli 32 128K esc -> 24khz to ByRPM
  • Dshot 1200 or max supported
  • Fettech Alpha with G4 1.7 N

would you keep a fix pwm frequency or variable?

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