PINNED - Plug & Play PGDT for Radio Control

[Burgerman]

Fair enough. What additional bits?

[woodygb]

It's a male DB9 plug that plugs into the Arduino interface instead of the Omni.

It has the addition of four screw connections ( similar to choccy block ) ...2 for supplying power to the Arduino via the same pins that the Omni would use ... and 2 that output the voltage swing ...which would normally input into the Omni.

Make any sense?

Additional bits are the USB interface and the DB9 plug mentioned above.

[Burgerman]

Yes.

Did you test this on an Omni?
Will it work also on a normal joystick?

[woodygb]

Not tested on an Omni ..as I haven't got one...but tested on a VSI .

It isn't however wired up for EASY direct interfacing with a Joystick pod.... IF everything goes OK then I'll continue on and make one for a pod.

So ...as I haven't got an Omni your a Guinea pig ... I've done my best to get all connections etc correct according to the literature BUT...

It will probably be a good idea to check my Arduino - Omni DB9 input/output.

Perhaps the initial test may best be done with the chairs wheels off the deck ....it's just possible that the Fore/Aft & Left/Right directions may be wrong.

There are two plugs inside the interface box that can be swapped over if that is the case.

I've chucked in a note with the parcel that instructs you to REVERSE the Elevator channel on your Transmitter before starting.... as that is my setup.

However you may need to play with the channel direction depending on the outcome of YOUR testing.

[Burgerman]

Yep all standard RC stuff...

[Burgerman]

I will do it outside. It wont start without accurate neutrals. Which if I remember correctly were nowhere near the real 2.5v real midpoint for some reason.

[rustyjames]

Woody, if you decide to sell any, I'm still interested and would be happy to send you some money up front for one.

[woodygb]

I will do it outside. It wont start without accurate neutrals. Which if I remember correctly were nowhere near the real 2.5v real midpoint for some reason.

Well lets hope it isn't to far away as the default neutral is SET @ 2.5v

[woodygb]

Woody, if you decide to sell any, I'm still interested and would be happy to send you some money up front for one.

Let us see how well the testing goes ... I really want this interface to be Super Easy ...as close to plug and play as possible and SAFE.

THEN ..I'll be happy to provide some.

B.M. has the experience etc to Beta test ... hopefully no problems will crop up.

[rustyjames]

Woody, if you decide to sell any, I'm still interested and would be happy to send you some money up front for one.

Let us see how well the testing goes ... I really want this interface to be Super Easy ...as close to plug and play as possible and SAFE.

THEN ..I'll be happy to provide some.

B.M. has the experience etc to Beta test ... hopefully no problems will crop up.

OK, great! I still might be buying a programming cable off you too. Since I've been snowed in the last few weeks I've been so bored I'm attempting to construct one, but not sure how successful it'll turn out.

[LROBBINS]

Woody,

If necessary you can add a neutral point calibration to your calibration procedure.

Ciao,
Lenny

[woodygb]

It didn't even cross my mind that I'd need one for the Joystick neutral voltage ....or I would probably have added something .

[woodygb]

I've ASSUMED that the Omni requires that 2.5v is ALWAYS Neutral ...with a swing off 1.2 v either side of this.

The calibration routine is for setting a R/C Neutral and for any discrepancy in the pulse spread either side of this R/C neutral point ( = 2.5v ) .... thus it should be mapped perfectly to the voltage output of 1.3v - 2.5v - 3.7v seemingly required ( according to the pdf's data ) by the Omni.

[Burgerman]

Well lets hope it isn't to far away as the default neutral is SET @ 2.5v

Well my receivers are all preset fail safe capable. Each channel goes to wherever I tell it.

So I can program my transmitters sub trim to give the right output (say 2.6v?) with everything centralised. And all trims disabled. I can set end points individually too. From 10 to 130% throw each way.

As it is with default settings its VERY accurate at exactly 1.500ms (+/- 0.001) centre point. Although I can change it to whatever works.

[woodygb]

Nope ...my program outputs 2.5v at the R/C Neutral point set during Calibration.

You can sub trim over BUT it will upset the program as it is expecting the R/C Neutral point that was set in Calibration = 2.5v ... not the new external R/C neutral = 2.** v that you'll be setting via the sub trim.

Fairly easy I think to add an external 20 turn trim pot to move the neutral voltage via reading it in software and applying an offset....
You'll need to return the interface to me if it requires modification together with a measurement of the Neutral voltage required by the Omni.

[Burgerman]

Nope ...my program outputs 2.5v at the R/C Neutral point set during Calibration.

Ah...

Well then it may well be an issue...
You will need 2 trim pots.

Also my interface uses the transmitter trims to find the exact centre. (So the brake trip happens with the same amount of stick movement in every direction from the centre). I then save that value as the new transmitter zero point. And disable all trims.

You will need to do this with trim pots?

[Burgerman]

Also the output on the Omni is 12v. Is there 5v available now on your board to take the RX power from? (and with 3 added sats?)

[woodygb]

Also the output on the Omni is 12v. Is there 5v available now on your board to take the RX power from? (and with 3 added sats?)

The board has a Traco Power 5W Switching Regulator, 6.5 to 36V dc Input, 5V Output, 1A ... as recommended by Lenny.

http://uk.rs-online.com/web/p/switching ... s/6664379/

Hopefully it will be sufficient ...

The RED wire number 2 in the pic on the 5 pin row of the DB9 is 5v output when the board is powered from the Omni or the extra DB9 plug that I've provided.

OMNI CONNECTIONS.png

[woodygb]

In the Arduino programming 0 = 0v 128 = 2.5v and 256 = 5v

Using a trim pot and software... I'm fairly confident the I can assign an offset value to that of 128 currently programmed .. by "reading" the pots voltage ..making 2.5v equal ZERO and anything either side as a positive or negative number that will be added or subtracted ..in software ... to my neutral value of 128.

[Burgerman]

Well first I will see if it works!

If not I can lie to it when calibrating, then revert to the real zero on my transmitter. So it will see centre stick as slightly off centre...

[woodygb]

Just be aware that FAILSAFE outputs 2.5v on loss of Signal / Receiver wire comes adrift ... so the chair .. if 2.5v isn't neutral ..could go wandering off if such occurs .

[Burgerman]

Yes. But if it needs some offset, then I will post it back, or add a couple of 5k 20 turn trim pots and a resistor or some such to the output?

[LROBBINS]

Woody,

If you still have the calibration only sketch from my CAN project, it does have a neutral point calibration sub-routine so you might want to take a look at it. I think it better to do this in software than to add trim pots that might drift over time. The CAN master module also allows one to set a deadband -- a minimal deadband (once neutral is calibrated) can make sure that the chair can't wander and that the brakes do get set even if the joystick has a gooey cam slider.

Ciao,
Lenny

[woodygb]

Lenny,

Just to be clear on this interface build ...there is NO additional separate joystick ..just a voltage swing output via a digital pot controlled by the R/C....
So I'm essentially attempting to interface a Radio controlled Joystick .

The biggest problem that I have is my lack of understanding about the Omni's Inputs and Outputs and whether I should be outputting a joystick reference voltage for the Omni ( which I'm currently not ) or whether it's outputting one for the interface to use ...which again I'm not using .

The Omni seems to have a built in Joystick calibration routine ... and I was hoping that running that would match /calibrate the R/C joystick outputs to the Omni.

6.1.1 Joystick calibration
Each time a new joystick type input device is connected to the Omni+ Module, the
system should be calibrated. To enter joystick calibration mode, switch the Omni+
Module on while depressing the Select button. After the normal power-up message,
the joystick calibration screen will be entered. At this point simply follow the instructions
on the screen and depress the Select button to accept the instruction.
Example: The first instruction is to center the joystick. The screen will appear as below.
Ensure the joystick is in the center position then depress the Select button. The next
instruction will appear as shown on the screen below.
Center Joystick
ok
Push Joystick F'ward
ok
Deflect the joystick to the full forward position, hold it there and depress the Select
button. The next instruction will appear etc.

I may need to ask P&G for clarification .

http://www.wheelchairdriver.com/pdf-files/omni.pdf

[woodygb]

@ Lenny ,

My problem arises from B.M's statement

. It wont start without accurate neutrals. Which if I remember correctly were nowhere near the real 2.5v real midpoint for some reason.

"Nowhere near" is hardly definitive .

I had assumed that Neutral is 2.5v as it is on my VSI ..and the voltage swing is 1.2v either side of this....

So...what are these accurate neutral values ....how do you find them ...is there a reference voltage that will give them or do you just need to use the Calibrate function of the Omni?

BTW... I have a R/C deadband value that can be altered in software.... the interface will only output 2.5v until this deadband is exceeded ... but I suspect that the Omni also has it's own built in joystick deadband.

[Burgerman]

Voltage unknown. Will measure. I say unknown because with a 5v supply tied to ground, the 50 percent duty cycle given by my speed controller at neutral stick, wouldn't allow the Omni to arm. You get the flash code saying that joystick off centre. I had to adjust it until it worked. Maybe that pin marked reference was important?

Yes Omni has a dead band. I would rather it had less of one.

A package has arrived!

[woodygb]

Excellent! .... Just set your super Transmitter up as a bog standard pulse spread with Ele reversed ... no offsets etc....

[Burgerman]

Ok...

As I suspected, if I connect to Omni, switch on, I get "JS REF ERROR" on startup which is what I get with the exact 2.5v when I tried this. It thinks its not zeroed.

So what to do?
Return, fiddle, connect RX and set a non real centre point? I suspect that will work but not the right way to do things.

Also, how do we know that the volt swing is exactly the right amount each way? I did it with trim pots, and watched the response. So that full stick didn't give out of range errors but full speeds/turn rates.

[woodygb]

Have you tried the Omni calibration routine?

I can only follow the specs provided by the Omni pdf.

For optimum performance, The Omni+ module should be calibrated for individual
joysticks. The voltage swing of 1.2V is a nominal value, actual values of between 1.1V
and 1.3V will be accepted by a calibration sequence.
If the voltage swing with respect to Vpin3 exceeds 3.0V, then the Omni+ Module will
assume a fault condition.

[woodygb]

Feel free to find the required neutral voltage by offsetting the transmitter.

I could then ... once you measure it ..use that voltage value as neutral.

Which would entail it's return.