Taranis home-brew DSMX (Spektrum DX4E) and RANGE CHECK?

[ImRich]

I hope someone can supply some guidance and help.

I have a Taranis usnig firmware 2.0.4

I made my own DSMX module using the DSMX module salvaged from a Spektrum DX4E along with a 3.3V BEC, a 1N4001 Diode and 4.7K resistor. It appears to fly ok, although it seemed to take some time to bind to my Spektrum receiver.

I'm using a Spektrum AR635 receiver.

My Question has to do with the RANGE check function. In trying to do a rang check, I was comparing it with another DSM2 Radio. On the DSM2 radio, I got about 35 paces.

I then rebound to my new DSMX module and the Taranis. I placed the unit in RANGE mode, and the warning beeps were occuring from my Taranis. After about 70 paces will full control I gave up!

The next day I looked at the output of the homebrew DSMX module with the RF Explorer spectrum analyzer and I couldn't see any diference in the output signal when I enable the RANGE check feature.

Attached are the captures from the analyzer, both with RANGE check mode on, and with RANGE check mode off.

Here is the RANGE check function on:

Range check function turned ON

Here is the RANGE check function off: (notice that it looks to have the same output levels as with the RANGE check on)

Taranis with RANGE check OFF

I don't see any difference in the output signal with RANGE check turned ON vs turned OFF when using the DSMX module and DSMX mode (I haven't tried other modes on the DX4E module yet).

By comparison, in D16 mode, the RANGE check mode seems to work perfectly:

Here is the D16 output with RANGE check OFF:

Taransi D16 mode RANGE check off

Here is D16 output with RANGE check ON: (notice that the output levels are significantly lower than with D16 mode with the RANGE check off)

D16 mode with RANGE check ON

Can anyone confirm that I'm doing this properly? How does one do a range check with a home brew DSMX Spektrum module on the Taranis?

[barjunk]

Have you tried any other versions of the software to see if you get different results?

Doubt it will matter, but it seems worth a shot.

Also, there is a newer version 2.0.5

Mike B.

[barjunk]

A couple more things come to mind...how are you verifying that the receiver is actually in DSMX mode?

Did you happen to take any readings of the radio before you transplanted the module?

Mike B.

[jhsa]

If you have a spectrum analizer you will know easily if it is in DSMX or aarrrghhh DSM2 this one just transmitts in 2 channels.

João

[ImRich]

Yes, from the images of the spectrum analyzer you can clearly see that I'm in DSMX mode.

But how do I get the module into RANGE check mode?

I haven't yet tried any other firmware.

[Kilrah]

By pressing enter on the [range] field as you did. Maybe somethng has been broken in the code, an issue has been opened to review it. Unfortunately I don't think anyone in the team has one of those modules to test anymore.

[bertrand35]

I just reviewed the code, it should work. When you go in [Range] mode, do you hear the special beeps?

[ImRich]

Yes, I hear the beeps. But as you can see, the signal output is as strong as it is when not in RANGE check mode.

Is there anything else I should check?

[bertrand35]

Yes, do we send the bit 0x20 in the first byte (which should be 0x38 in DSMX mode) of each frame?

[ImRich]

How can I check this? I have an old Tektronix oscilloscope, but nothing that could read a data stream, unless I can sniff it with FTDI USB cable or something?

I'm happy to do some legwork to help debug this if you can tell me what to do.

I thought that the spectrum analyzer output was very telling, and the reason for posting the D16 scans was to show that the RF Explorer could see evidence of a transmitter in range check mode.

[bertrand35]

You just need a logic analyser for this

[Hawk600]

I was running 2.0.3 (2.0.5 now) and the range check mode worked for me using a dx5 hack module and DSM2. I got between 30 and 40 steps.
At the limit the communication gets spotty and longer than that there is no response from the plane.
Just for the record I compared the DX5 hack with 2 HK orange tx modules (those do a range check with the bind button pressed) and besides people says different the Orange TXs had better range than the hack module.
I was able to walk up to 60 steps before loosing signal, but in a nutshell, yes the range check works, same as using a FrSky radio/rx.
I will try it again with 2.0.5 and DSMX and will report back.

[Kilrah]

Just for the record I compared the DX5 hack with 2 HK orange tx modules (those do a range check with the bind button pressed) and besides people says different the Orange TXs had better range than the hack module.

Note that there is no guarantee that the range check on both puts out the same level.
The Orange TX could be reducing output power less than the original.

[Hawk600]

You are right Kilrah but I also tested it many times near my house without range check pressed, walking as far as necessary before breaking or loosing signal and the HK ones went far away, I am guessing 20 to 30 %. I was really disapointed with the test results because I was especting the spektrum chip to have more power output.
In order to perform this test I used a phone under the plane to monitor servos and throtle response and walked away monitoring with my cell phone the tx commands and the plane response. A very improvised method but it works.

[ImRich]

I don't have a logic analyzer so I can't check the data stream. So someone else confirming that this is either working or not would help a lot.

My DSMX module came out of a DX4E. I believe the label on the module itself said DX5E.

Other than the range check, it seems to be working well. Although it did seem to take more time than I would have expected to bind with my receiver. I have flown several times with it without any issues so far (other than the range check issue).

[ImRich]

Here is an update. I just updated my transmitter to version 2.0.5 and checked again with the RF Explorer spectrum analyzer. It now looks like I get about a 25 dB difference when I turn on range check mode.

I can't confirm this yet with my receiver, as the receiver I used is about an hour away from me right now.

I don't know why this is different with firmware 2.0.5, and perhaps it's not the firmware, but I thought I would provide this update.

[barjunk]

ImRich,

Did this resolve?

Mike B.

[ImRich]

I have not yet been able to test with my DSMX receiver, so I can't be sure yet.

[ImRich]

I was able to do one simple test this weekend using 2.0.5 firmware. I walked about 100 feet away with the RANGE check on until I lost control, then I turned off RANGE check and control came back.

So I think this is working again. Sorry if this was a false alarm.

[bertrand35]

We didn't change anything, so it's perfect

[ImRich]

I understand that nothing has been changed, but it sure looks like it is working differently (both on the spectrum analyzer and in use at the field).

Either way, thanks for your work. If this changes I'll report back.

[randallpatrickc]

I have just built a DIY module from a DX4e and my test flight crashed and burned. I must confess that my range test comprised just a taxi and wiggling . I would be very grateful for a pointer to how to do a range test - this is my first foray away from my old 20 year old FM Tx. I see there is a [RANGE] option on the Taranis but I'm unsure how to use it with the DSM module. The model is an E-Flite BNF Carbon Cub and the Rx is buried inside. It's awaiting a new prop adapter and some foam friendly CA right now.. It took off fine and completed 1/2 a circuit before going into an unrecoverable knife-edge. The rudder seemed to be jammed over. All controls operate normally on the tabletop.
Does the [RANGE] option simulate collapsing the antenna on a FM Tx?

[Kilrah]

You might want to read up on range check procedure in the manual of a Spektrum radio.