Backfitting X-Lite Bluetooth

 

In a modern transmitter which design and concept mainly appeal to the offspring, the trainer / student mode is certainly high on the wish list. The product strategy of FrSky seems all the more incomprehensible, just to equip the X-Lite neither with the necessary DSC socket nor with a Bluetooth module.

Of course you can help yourself by passing the signal of a receiver bind to the X-Lite to the DSC socket in the trainer transmitter - corresponding instructions can be found on the Internet.

However, it is also possible to retrofit the X-Lite with a Bluetooth module and then use Bluetooth to set up the trainer / student mode with another suitable transmitter. As far as I know this is all Bluetooth-enabled Horus and Taranis radios (except the X9e).

Whether in this way also telemetry data can be transmitted to suitable Bluetooth devices, I do not know and I have not tested.

The following tutorial describes step-by-step how I proceeded to extend my X-Lite and should be easily understood by any skilled hobbyist with some experience in soldering.

Attention:
The modification requires intervention in the hardware, which are not provided and supportet by the manufacturer and lead to my knowledge the loss of warranty. All replicas are therefore always at your own risk!

What is needed?


A suitable module and antenna are available from FrSky as replacement parts for the Horus X10, X10S and X12S.

As can be seen on the picture on the right side, my copy is the version "FrSky_WTv2" as of 11.04.18.

 

Step 1 - opening the transmitter housing

Opening the case of the X-Lite requires a bit of sensitiveness. On the Internet you will find the appropriate video tutorials, which should therefore be a good look in advance. There is also a very good illustrated guide, just google for "FrSky X-Lite Teardown Guide".

Attention: Please do not forget to remove the SD card - otherwise i
t will be damaged!

By the way, I like to use relatively hard guitar picks (for example the black Dunlop in 1.5 mm thickness) to pry open the case halves, which are still much softer than screwdrivers and similar tools and therefore leave far fewer marks or even damage to the plastic housings.

Caution: All connections should not be removed by pulling on the wires, but by carefully grasping the plugs themselves with a fine pair of pliers.

 

Step 2 - Removing the X-Lite motherboard


If the housing is open, first remove the four screws of the two battery holders and the board for the connection of external modules (in the areas marked with red circles).

Then carefully loosen the corresponding connectors.

 

Then carefully unscrew the U.FL plug of the internal antenna from the RF board, which has been secured against slipping with a yellow ground, and the two screws.


Now, the RF board can be lifted gently to release the connector on the bottom, and then removed completely.

 

Carefully cut and remove the two cable ties without loading the attached gimbal cable.


Then the two screws can be removed and then the holding frame can be removed downwards from the transmitter.

 

From the now accessible mainboard, carefully remove the connectors of the two gimbals, the two switch boards, the speaker and the two already disconnected connection cables to the RF board and module slot.


In addition, the module firmly soldered to the mainboard vibration module is removed from the rightmost out of the case. The module should be moved very carefully during all further steps so that the solder pads of the connection cables are not torn off the circuit board.


Finally, remove the six screws marked with yellow arrows.

 

The next step is a bit fumbling again. Carefully lift the mainboard only at the front. At the bottom you can now see the sensitive connector to the display.

To remove them, first loosen the lock by pulling the black part of the socket a few millimeters forward from both sides of the socket (as indicated by the red arrows).

Then the foil conductor can be carefully pulled with tweezers or similar from the socket.

 

 

An additional picture shows once again how the released locking of the socket must look in order to remove the foil conductor.

Finally, the mainboard can be removed from the transmitter.

Step 3 - Solder BT module

The actual soldering of the module itself is much less demanding than the disassembly and subsequent assembly of the transmitter. On the upper side of the mainboard, the intended module position is very easy to identify at the top left. Align the module as accurately as possible to the pre-tinned contact surfaces, provisionally fix with a piece of adhesive tape and then solder to the ten contacts with the lateral contact surfaces of the module. It is understood that this must be done carefully and sparingly with the solder, so as not to short-circuit between the contacts. That's it already.

 

Step 4 - positioning the Bluetooth antenna

The BT antenna consists of a narrow, self-adhesive film with a relatively long antenna cable.

Since I could not make out a spot in the transmitter housing that was obviously intended for the antenna of the BT module, I opted for the vertical surface on the front of the transmitter just above the power switch.

The BT antenna is thus parallel to the internal RF antenna and is not shielded by the user's hands or body during operation.

Step 5 - Assemble the transmitter

The assembly of the transmitter is simply in the reverse order as the disassembly.


The BT antenna cable I have first to the left and immediately in a bow back to the right side of the transmitter. After installing the motherboard, I could put the cable around the storage battery and it ended up exactly in the right place at the U.FL socket of the BT module.

Both antenna plugs were fixed after installation with a drop from the hot glue gun. This method has proven itself, as it reliably secures the antenna plug, but can be solved if necessary without damage.

When assembling, special attention should be paid to:

  • check that the display is clean in its frame before installing the mainboard
  • carefully insert the foil conductor of the display with tweezers into the socket, without force and especially
  • route all cables exactly as they did before disassembly
  • after connecting all the connectors on the mainboard, connect the batteries provisionally (do not confuse them!) and test whether the transmitter can be switched on, the display works and all keys can be operated (the RF board is not required for this)


Here are some pictures of the assembly:

 

First test


Boot the transmitter and select "Trainer" under "Bluetooth" in menu 8/9 of the system settings.

I could not dial the two address options with my system (that's the same with my Horus X12S).

Finally, you can enter a name for the radio.


Then just scan with a smartphone. In the first tests, the system was recognized only with a generic name (FrSky-BT or something like that), meanwhile I see it with the name given by me "xlite".