Blogs

Until now, the only way to connect APM or Pixhawk via wireless is using radio modem. Well, you can also use blue tooth but the range is very limited. It may be good for set up or so but certainly not flying if you wish to view live data. 

For long range FPV or aerial mapping mission, I use RFD 900 radio modem. It has served me well and depends on local environment, I can receive live data up to about 10 KM. It is sufficient for our job most of the time. 

The Dragon link V3 advanced system was released early this year. Beside the usual long range ( they claim up to 50 KM ) radio control, their receiver is equip with bi direction data transfer capability. Once set up, it can virtually replace the long range radio modem. Another added benefit is their transmitter has build in blue tooth so we can use our note book computer to connect with GCS such as Mission Planner or using hand phone / tablet with Tower. This is a full bidirectional connection, so we can view live data AND also upload command or flight plan. 

The bi directional data transfer feature is fantastic to me but unfortunately the earlier version of their firmware didn't help much to get thing set up. Some user had successful link it up with computer or tablet but the blue tooth connection is not reliable. I have tried earlier but no luck. 

Early this month they release a new updated firmware with lots of improvement especially the data modem feature. A user call Noircogi kind enough to post a detail set up guild in RC Groups, which is also found in Dragon Link support page. I follow each step but still can not get it connect to my computer or tablet. After a few post in RC Groups, Noircogi and other help me with some suggestion and point out some error in my set up and now I can get reliable connection. There is actually nothing wrong with Noircogi instruction, just that I misunderstand some points. Therefore I think it may be good if I can put up a graphical guild for those who wish to try.

The work flow of the set up is :

• Connect the transmitter with computer / tablet / hand phone blue tooth
• Connect Pixhawk telem 2 port to receiver
• Configure Dragon Link receiver
• Configure Dragon Link transmitter 
• Configure Pixhawk parameter
• Configure Mission planner parameter. 

Now, lets get start

Connect the transmitter with computer / tablet / hand phone blue tooth

 ( All italic text is copy from DL support, for which I believe is contributed by Noircogi. )  

I set CH 5 as " Serial OUT " and " CH 6 as " Serial IN " You can set to other CH. In the PPM Channel, select 12. This step is not mention in the instruction and I was told it has to be the same number of channel in the transmitter, which we are going to set as 12 CH later. I am not using TX / RX with reference to pin number. This is because I found contradict info which confuse me. TX and RX can be either no 2 or 3. I'm sure those technical guy can easily know which is which by I rather just use number. No 1 is the outer most pin and progressively go toward the centre of the flight controller where no 6 is the inner most.

Save the setting and reboot.

Configure Dragon Link transmitter

On the Dragonlink Transmitter GUI
Main page under RF select; 12 Channels, High Bidir Bandwidth, Fastest Update-Rate
'Radio modem & Telemetry" page select; Bluetooth: Radio Modem, Baudrate: 57600
Save and reboot here too.

Re-bind your Dragonlink receiver to the new TX settings.

You'll need to rebind to transmitter with the receiver again to let the new setting come into effect. 

Configure Pixhawk parameter.

You can configure those parameter by using USB cable plug into Pixhawk or use the normal telemetry. Once connected with Mission Planner, go to Config / Tuning then Full Parameter list and change the value as listed below. 

BRD_SER2_RTSCTS        0
SERIAL2_BAUD              19
SERIAL2_PROTOCOL       1
SR2_EXT_STAT                1
SR2_EXTRA1                    5
SR2_EXTRA2                    5
SR2_EXTRA3                    1
SR2_PARAMS                   8
SR2_POSITION                 2
SR2_RAW_CTRL               1
SR2_RAW_SENS              1
SR2_RC_CHAN                 0

Configure Mission Planner

Under the same tab, go to Planner and set the following :

Attitude to           5

Position to          2

Mode/Status to   1

RC to                 0

Sensor to           1

Now the moment of truth, Ensure your computer had pair with the transmitter with blue tooth, you can check in blue tooth setting. My Tough Book still running Win7 Pro so it looks like this :

For me. the computer had assigned COM 40 as the blue tooth COM port. So in Mission Planner, select the appropriate port and select 57600 baud rate and hit CONNECT. It should be connect within a few seconds. Now you had full data link. Shall we throw away our traditional telemetry ? No, I don't think so. first and foremost the DL system need more 

time to test for stability more user friendly in term of set up. For serious FPV fun or aerial mapping work where expensive equipment on board, a back up system is never a bad idea. 

. 
Now you can test it out

Power cycle everything. Make sure your PC's bluetooth is paired to your the DL transmitter (for now, you can only do that with the DL receiver powered off).

Launch mission planner.
In the upper-right corner, select the first bluetooth serial port which shows up. Select 57600 baud.
Power on your plane.
Power on your DLA transmitter.
As soon as you see the blue telemetry light show up on the TX, hit "Connect" in mission planner.

It should come right up and work. If it fails right away, select the other bluetooth serial port, power cycle the DL TX and hit connect as soon as you see the blue light.

The settings above give you 5HZ updates on the artificial horizon, 2Hz updates for GPS and 8 parameter downloads per second. At first I had everything much slower but with these settings it's nearly as fast as I was getting with the separate 3DR telemetry radio!

Dropped telemetry packets don't seem to cause any trouble at all.

Noircogi has a nice video which show the full telemetry function using Dragon Link. Data update rate is not much difference, If any, compare to conventional 915 / 433 Sik radio modem.

I think Dragon Link Advanced system may worth consider. Just look at the price of a of pair RFD 900. User had reported
about 10 KM data range for which the out put power of the micro receiver only 25 mW. The soon to be available full size
receiver with up to 1 W out put power should give us a lot more range.

https://www.youtube.com/watch?v=jXO6cTJ7Ze0