Hi all,
I just bought an FrSky Taranis for my quad copter and needed to get the Mavlink data up on the Taranis LCD telemetry display. So here is my solution using a Teensy3.1 as a converter between MavLink and the S.Port on FrSky X8R.
See attached file below...
Replies
No one has any ideas?
On the subject of the FrSky SBus to CPPM convertor.
My new Rigol 1102E oscilloscope tells me that I have a 28 millisecond frame rate with the link connected, which I use with the APM2.5 and a 21 millisecond frame rate with it removed. I am happy with that but can anyone tell me where this is written down. I can't find it in the FrSky documents. I would like to be sure - my ocilloscope skills are a little rusty.
Alan
It's on a picture here http://www.frsky-rc.com/product/pro.php?pro_id=112
I am using an APM 2.6 and do not have the jumper installed. Is that correct? Does that mean it is 21ms? When would I use 28ms?
Fred,
You might not have an issue using 21 milliseconds....................
However, when each channel is operated the pulse width for that channel alters. At the end of the train of pulses is a sync pulse or space, which tells the APM when to expect the start of the next train of pulses. It is not of fixed width but takes up the remaining available milliseconds from either your 21 millisecond pulse train or your 28 millisecond pulse train, which ever has been set. If for example, all of your available channels are at maximum pulse width (about 2 milliseconds for each channel) and you have a 21 millisecond total pulse train length, the sync pulse can become indiscernible from the channel pulses and the flight controller can hiccup and loose sync, which can have unfortunate results - particularly if you don't setup the APM failsafe!
FrSky, which uses a 21 millisecond pulse train as standard, acknowledges this and has provided firmware updates for its receivers with CPPM capability and the choice on its SBus to CPPM converter to use 28 milliseconds and have a nice long sync pulse/space. It is not an APM issue, more the manufacturers original choice of pulse train length - the same issue occurs on a KK2.0 board. I don't know about the PixHawk, which can use the SBus directly - anyone care to comment?
The only downside is that the number of updates per second from your transmitter sticks to your model's control surfaces reduces slightly. Given that APM users are generally flying a self-levelling attitude-aware robot, it it not much of a loss.
Bottom line - use 28 milliseconds (jumper connected) for an APM2.5/2.6 with any receiver on CPPM.
Alan
Alan
Your comment about the APM failsafe got me thinking. I have set up the failsafe in the event the Taranus tx signal is lost/turned off. Is there some other failsafe mode I should set up?
Fred,
I believe you can setup failsafe on the basis of a low battery as well, if you have the 3DR Power module or an Attopilot module fitted but I haven't set this up on my quad. See the failsafe page in Mission Planner.
Alan
Wow! Thanks for the very detailed reply. I learned a lot. Installed jumper.
Aloha Fred
Brano,
thanks - saw that and thought it was a little ambiguous. However, maybe not given the scope reading.
Regards
Alan
I'm having quite often issues where the Teensy won't initialize. I have to unplug and replug Teensy to receiver, then it starts working.
To be precise, after plugging in main battery none the LED on Teensy won't light up at all. After re-plugging Teensy to receiver it starts working. Replugging the main battery doesn't help, I have to replug it to receiver (while main battery is connected).
Thoughts please? This is driving me crazy. ...FYI Teensy otherwise works nicely once it is initialized.
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