RunRyder RC
 2  Topic Subscribe
WATCH
 1 page 338 views
Scorpion Power Scorpion Power
HelicopterRadio - JR DMSS › DMSS Telemetry Sensors
07-07-2017 03:30 AM  4 months agoPost 1
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

Hi All,

Does anybody know what is the communication protocol between the DMSS sensors and JR receivers? I gues is something like I2C but not sure.

Thanks

Marco

PM  EMAIL  GALLERY  Attn:RR  Quote
07-07-2017 05:57 PM  4 months agoPost 2
Pistol Pete

rrProfessor

Seffner, FL

My Posts: All  Forum  Topic

You "might" find your answer here
https://www.rcgroups.com/forums/sho...to-RC-Protocols

~~Enjoying the hobby one flight at a time~~

PM  EMAIL  HOMEPAGE  GALLERY  BLOGAttn:RR  Quote
07-07-2017 10:49 PM  4 months agoPost 3
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

Thank you for the info!! Unfortunately there is no JR DMSS there and what I'm looking at is the protocol between the sensor and the receiver being transmitted via the sensor wire. The JR receivers use a standard servo "port" (3 wires) to connect the receivers and it somewhat recognizes different sensors connected in parallel. I'm just trying to understand how that works and maybe create some home made sensor options, since the JR ones are not that many.

Thank you!!

Marco

PM  EMAIL  GALLERY  Attn:RR  Quote
07-10-2017 11:21 PM  4 months agoPost 4
Pistol Pete

rrProfessor

Seffner, FL

My Posts: All  Forum  Topic

Doing a little research out of curiosity I have found out that JR is using same protocol as Hitec Aurora Tx.

Perhaps searching for Aurora protocol you may find what you're after in rcgroups.

~~Enjoying the hobby one flight at a time~~

PM  EMAIL  HOMEPAGE  GALLERY  BLOGAttn:RR  Quote
07-11-2017 12:00 AM  4 months agoPost 5
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

Proprietary to JR.....

Get a sensor.....open it's package....identify the ICs used....go to the IC's manufacturer's website....download the data sheet....

That would be the first thing I would do....

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-11-2017 03:58 AM  4 months agoPost 6
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

I will try both of those paths!!! I will open a sensor I have to see what's inside.... And search for the hitec stuff... Hitec has a current sensor that is one that I'm interested and Jr does not have it...

PM  EMAIL  GALLERY  Attn:RR  Quote
07-11-2017 04:17 AM  4 months agoPost 7
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

The JR sensors will probably all have the same IC to control the flow of telemetry data....and have whatever circuitry to provide the data.

Plus, whatever ancillary circuitry to make it works.

Hopefully, for your purposes, they won't have obscured the IC part numbers.

For instance, Blade used to do that.....but, if one looked at several "3 in 1" boards....one could get part of the IC # from 1 board....another part from another board, etc.

And then put all that together to ID the IC.

Once you get that, it's easy to look up the spec. data sheet online to learn how to program it.

In fact, the IC manufacturer usually has "starter board kits" for experimentation to get people to use the IC for whatever application it could be used for. Plus, they'll have some "started software" to use to get you started.

And, if you call the IC manufacturer tech support, they'll give even more info.

Best of luck.....

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-11-2017 08:20 AM  4 months agoPost 8
Pistol Pete

rrProfessor

Seffner, FL

My Posts: All  Forum  Topic

PM  EMAIL  HOMEPAGE  GALLERY  BLOGAttn:RR  Quote
07-12-2017 04:29 PM  4 months agoPost 9
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

BTW, I2C uses two signal wires to transfer data.....a clock signal coupled with a data signal.....rather than the 3-wire interface used by a satellite RX.

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-12-2017 06:48 PM  4 months agoPost 10
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

Can the ground wire be used as one of them? In that case it would still be possible to use 3 wires in that config if you add just the power supply line to the 2 I2C signal ones..

PM  EMAIL  GALLERY  Attn:RR  Quote
07-12-2017 07:29 PM  4 months agoPost 11
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

The ground? No.

The purpose of using a "clock" signal is to "indicate" to a "data receiver" that the "data" present is "valid" at that instant.

So, at that instant in time, the "data" can be "latched" correctly.

Without the "clock" signal, the incoming "data" must be severely "oversampled" in order to determine precisely when the "leading" edge of the "data" occurs.

Using the "clock" signal greatly increases the "data" transfer rate compared to that of "oversampling".

An software analogy would be that of processing an "interrupt" by a microprocessor.

The uP software could continuously monitor the "interrupt" by the "skip on flag" method....but, if the interrupt was missed by the last check of the "flag", there would be a delay due to the micro instruction cycle times to re-check that "flag".

And this delay would be variable in time.

On the other hand, if the circuitry was such that the uP interrupt software was immediately executed, the delay would be fixed in time....which would lead to faster interrupt processing of external "events".

Sorry for the tech jargon....

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-12-2017 10:40 PM  4 months agoPost 12
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

Thank you for the engineering class!!! I like that technical side of the hobby and that is why I try to do this type of stuff. I'm an engineer (aerodynamics/flying qualities) too but electro/electronics are not my strong side so I'm learning a lot in the process. Since you open up that side of the conversation, how do you imagine the serial data works on the JR stuff? They have the power cables and a single data cable right? I believe the sensor signal is not duplex since it does not need to receive data from the radio.. How would you align the data packets and extract the good ones? From the links posted above I see that JR TM is limited to 16 sensors so I guess it is a series of 16 values plus a parity bit? Something like that? Sorry for my ignorance but I'm really starting fresh in this serial communication tech...

Do you think I can emulate that with an arduino?

Thanks again

Marco

PM  EMAIL  GALLERY  Attn:RR  Quote
07-12-2017 11:43 PM  4 months agoPost 13
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

"how do you imagine the serial data works on the JR stuff? They have the power cables and a single data cable right? I believe the sensor signal is not duplex since it does not need to receive data from the radio.. How would you align the data packets and extract the good ones? "

Assuming the sensor data is not duplex.....and even assuming that JR's Xbus servos are not duplex(like "normal" servos with separate cables).....one way to receive data from separate devices along a common cable......or to send data to separate devices along a common cable.....is to "address" each device separately.

In the world of computer automated instrumentation control and data acquisition, among many applications, this is implemented....such as the GPIB(General Purpose Interface Bus).

With GPIB, all the instruments are "daisy chained" together via the exact same cable.

Another way is like the old style ethernet cables were connected via a common cable....

Even still is yet another method which involves the RS-232 method of "serial communication" which might seem odd, but it can be done....and I will use this as an example, as I have designed several such interfaces.

And because you mentioned the use of "parity" bits....lol

What can be done is to assign a bit(in the serial bit stream) as a "command/data" bit. When it's a logic "1", any bits in the 8 bit stream are considered a "command"....and when a logic "0", any bits are considered data.

A device is first "commanded" to receive the data sent....and at the same time, all others by default ignore the data.

In the same way, the instrument "addressed" only sends data back....all others remain "silent".

In other words, "don't speak unless commanded to speak"....because "you will be ignored if you do so"....

But, you've lost a bit for this purpose, so the max # of command/data bit combos are 128...0 - 7F hex.

Which limits you to "string" together a max of 127 instruments/devices, etc....and the data is limited to separate bytes of 0 - 127. Need more data, send/receive more "data bytes".

Need more instruments, forget about this method...

GPIB does this also, except it sends/receives data bit parallel but byte serially.

With regards to this RS232 analogy, use can use another serial transceiver that sends/receives "data" in 16-bit serial "packets"....

So, now you can interface many more than 127 "instruments"....via the common cable.

It's up to the software and hardware as to how to make all this stuff work together.

Assuming something similar is done with the JR XBus tech.....using a common cable is the keyword....I would assume that something similar is being done....only using the latest methods of serial communication technology.

Most likely proprietary to JR....in the way JR implements it.

When sending data to servos, you don't need 127 servos.....but for servo precision, you might need much more that 127 bits.

Perhaps they are using ICs that are capable of 16-bit transception....16-bits - 1 bit = 15 bits = 0 - 32768 bit resolution.

To send data to servos, each servo is first "addressed" to receive its intended data...the data is sent only to the intended servo...and when another servo is addressed, all others cease to listen to any data.

Likewise, as sensor is "commanded" to send its data....and all others, by default are told to STFU.

Unlike RS232, via a clock signal line(or even without such a line), this can happen very, very rapidly......

With the end user, the heli pilot "feeling" that the response is better than they have ever "felt".....because the data gets moved around so fast.

And all this stuff should be present in the serial bit stream....that streaming at a rate that it doesn't even look like the normal PWM signals that are sent the "old way".

That's my assumption as to what's going on....or that's perhaps another way of doing a similar thing....

Can you do what you are attempting to do?

Sure...but you've got a whole lot of work to do....given that you first have to understand what JR is doing...and then you have to integrate your device....using JR's way of doing things.

And that is no easy task.

But, if you are successful, you will be easily able to get a great, high paying job as a JR design and integration engineer...

And then, you won't be able to talk to us about it any more....because it's proprietary....and you'll have to sign non-disclosure agreements....LOLOL

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-13-2017 03:39 AM  4 months agoPost 14
mpafonseca

rrApprentice

Savannah, GA - USA

My Posts: All  Forum  Topic

One more time Thank You a lot for the explanations!!! I really regret not paying more attention to the basic electronics classes I had in College and even doing more of those... Its really interesting stuff... And sorry for my maybe not properly used terminology... I'm a total dummy at this so the probability I will be able to do it is minimal... LOL but its fun to try...
Cheers!!

PM  EMAIL  GALLERY  Attn:RR  Quote
07-13-2017 05:50 AM  4 months agoPost 15
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

"I really regret not paying more attention to the basic electronics classes I had in College "

I didn't learn that stuff in college....was into semiconductor physics there......

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-13-2017 05:55 AM  4 months agoPost 16
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

"I'm a total dummy at this so the probability I will be able to do it is minimal"

The game ain't over 'til the fat lady sings....

Like I said, the first thing is to ID the ICs in the sensor and to check out the IC manufacturer's data sheets.

Then you can get the applications engineers at that IC company to steer you in the right direction.

That's what I always do.....and it always works for me....to the extent possible.....then you're on your own....

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
07-13-2017 05:59 AM  4 months agoPost 17
EEngineer

rrProfessor

TX

My Posts: All  Forum  Topic

I have to add this....you're gonna need some test equipment.

A digital logic analyzer and an Oscope, at least....and they aren't cheap....

Logo 600SXs, 800XX, TDR IIs

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 1 page 338 views
Scorpion Power Scorpion Power
HelicopterRadio - JR DMSS › DMSS Telemetry Sensors
 Print TOPIC  Make Suggestion 

 2  Topic Subscribe

Saturday, November 18 - 5:58 pm - Copyright © 2000-2017 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online