FrSky SBUS to PWM decoder?

[RGN01]

I can't get my FrSky SBUS - PWM decoder to work - can anyone see what I'm doing wrong, please?

The RX is a X8R. I first set each channel of the decoder using the FrSky SBUS Channel Changer and confirmed that each was set correctly. I then attach the decoder to the X8R SBUS port, attach a servo to any channel of the decoder and power up. All that happens is all the LEDS on the decoder light solid green and the servo/s buzz.

I can't get anything more than that to happen. Any ideas?

Thanks

Richard

[Kilrah]

What are your servos? You should only use digital servos on the decoder. The buzz is typical of analog servos not appreciating the fast refresh rate.

[RGN01]

Thanks, Kilrah.

I thought they were digital but I will need to check that, then. They are flap servos buried in a wing so I'll have to dig them out to confirm.

Richard

[Kilrah]

You might want to move channels around to connect the analogs directly to the receiver and keep the decoder pins for the digitals if you have a mix.

[RGN01]

Thanks again, Kilrah.

They are Savox digital servos. I get no movement at all, just a high frequency buzzing. They work fine attached to the RX directly.

I wonder if this is something unique to Savox? I will have to try to find another make of digital servo to test with.

Richard

[RGN01]

Just tried a Futaba S3050 digital servo. It goes to full deflection the doesn't do anything - it is also silent.

I'll keep trying!

A question, if I set one of the decoder output channels to the same as one of the RX channels (say channel 5), should the two outputs then both work? This isn't what I'm doing now - I'm using channels 9 - 12 on the decoder - but it may be a help when fault finding if this works.

Richard

[tilmanb]

My decoder worked when I added some mixes at channel 8 or so. Try that.

Written on my mobile. Please excuse my brevity.

[RGN01]

Actually just had another thought - I'm using the built in module on a Taranis and it is set to XJT-D16 mode with channels 1 - 8. Should I increase this to 1 - 12?

Thanks for the response, Tilmanb - I have a mix set up on channel 9 - 12.

Thanks again.

Richard

[RGN01]

Guys, thank you - just talking about it helped!

Changing the channels output on the TX module page on Taranis sorted it!

Richard

[Kilrah]

Yes of course, if the radio doesn't send out channels 9-12 it will be hard to use them on the other end

[tilmanb]

I had my recriver set up so it mirrored the first eight channels on sbus. I had a different issue. But glass you worked it out.

Written on my mobile. Please excuse my brevity.

[PhilG]

See
http://www.rcmf.co.uk/4um/index.php/topic,101234.0.html
Post 1: frame-rate divider for individual servos
Post 3: frame-rate divider for SBUS itself, affects all servos connected via the Frsky SBUS-PWM decoder

Both give an 18ms frame servo signal suitable for conventional servos

Cheers
Phil

[MikeB]

Can you tell which is the "first" of the repeated SBUS frames? I ask because if you pick the "second" one all the time you will add 9mS to the overall system latency.

(Off Topic)
I take it you are the PhilG I saw frequently on the GiantCod forum.
(/Off Topic)

Mike.

[PhilG]

Hi Mike, yes thats me. Cod was a long time ago, it used to be a great forum but went down the pan as soon as MHS took over.
The widget passes the very first burst it sees, and every subsequent 'odd' burst.
I'd not realised you were so heavily involved with the openrc projects, good work.
Cheers
Phil
http://www.singlechannel.co.uk

Edit - having to have my comments 'approved' is tiresome!

[jhsa]

Just the first 5 posts or so..

[Kilrah]

2 posts actually.

The widget passes the very first burst it sees, and every subsequent 'odd' burst.

The problem is that if the radio is set to send up more than 8 channels each frame updates only 8 channels, while the other 8 are just a copy of the previous values. As it is you have a 50% chance of always taking the "copies" rather than the "originals", and by that adding 9ms latency.

[Erni]

I was wondering if it was easyer and cheaper just to drop the SBUS decoder and use an Arduino mini instead.
There already is SBUS library to decode the sbus signal, and the Arduino servo library use the good old 20ms rate.
The only thing missing is a simple inverter.
I have tried it with just a single servo, just to see if it worked, and found no problems,