Modifying a FrSky DJT Module for Telemetry
For telemetry data from the model to be conveyed from the module to the 9XR Pro transmitter for display and sounding of warnings, additional connections are required. These can be provided by a cable from the Futaba port on the transmitter to the socket on the DJT module. Alternatively, the module can be modified to eliminate the need for a cable. Doing so will void your manufacturers warranty.
The Turnigy 9XR Pro already has the internal connections needed to accept telemetry signals from the module. The Ersky9x firmware already has the coding needed to display the telemetry data not only from all the FrSky sensors but also from the Winged Shadow How Hi altimeter.
Circuit Diagram:
Parts Required
R43: 2,700 Ohm 1⁄2 Watt resistor R44: 4,700 Ohm 1⁄2 Watt resistor D3: BAT85 Schottky Diode (1N5819 Schottky diode may be substituted) Note: The diode is only required if the module is for use in a Taranis transmitter.
Opening the DJT Module
Undo the screws and release the back cover. It is connected to the circuit board by a short coaxial cable to the base of the antenna. It is possible to complete the modifications without releasing this cable. The small U.FL connector used at the circuit board end has limited life and should not be removed frequently, so it is desirable to leave the the antenna cable connected. The circuit board, which lies in the bottom of the plastic box, is retained by detents moulded into each end of the box.
The switches and LED assembly are mounted on the this board too, so that when you remove the board they will be removed with it. Hold the box lengthwise with both hands, your thumbs on the top edges and fingers pressing underneath the base of the box. Push upwards with your fingers, bending the base of the box upwards and hence pushing the circuit board up. With enough force the circuit board will spring out of the detents at one end. Remove the box.
Adding the Components
Orient the circuit board with the switches toward yourself and the top away from you. The board is now oriented the same way as the circuit diagram above. There are four pins at the top left of the board and five sockets on the bottom right.
Solder the 2,700 Ohm resistor between the base of the top left pin and the pad adjacent to the second socket from the top on the right side of the board. Ensure that the end of the resistor is soldered as low as possible on the pin. Solder the 4,700 Ohm resistor between the base of the second from the top left pin and the pad adjacent to the bottom right socket. (Do not use the adjacent hole with copper trace around it, as this terminal is not connected to the bottom socket.)
If you intend to use this module with a FrSky Taranis (possibly to enable use of older V8 series receivers) you must fit the diode.
The “base” end of the diode is the one with a ring (in terms of the diode symbol, it's the end with the thick bar at the point of the triangle). Bend back the wire from this end parallel to the body of the diode. Cut the two wires so that the diode can be installed vertically, as shown. Spread the wires apart and solder the short wire to the pad adjacent to the second lowest socket. Bend the longer wire to fit and solder it to the end of the resistor adjacent the lowest socket.
Assembly of the Module
One end of the circuit board has the corners removed to fit the pillars in the box for the back cover screws. Place the circuit board inside the box and carefully push it to the bottom so that it rests parallel with the bottom of the box. Be careful not to apply force to the antenna cable and clip. Using a thumb at each end push the circuit board until it engages the detents.
At the end adjacent to the switches, the cover has tags which slot into the module box. Insert these tags holding the other end at a slight upward angle. Ensure that the switches align with the openings in the cover and close the top end of the cover, making sure the antenna cable is free inside the box. Insert and tighten the screws.
If you have more than one DJT module, mark this one as being modified.
Use of the Module
In addition to the Turnigy 9XR Pro, this module may be used with the FrSky Taranis and the SKY 9x boards. It should NOT be used with the regular Turnigy 9XR or the various 9x transmitters, as the pin connections are not compatible.